Term 1 Flashcards
Commensal microbes
help defend the first line of defence:
• Secrete antimicrobials (S. epidermidis)
• Alter surface chemistry (Cutibacterium acnes)
induce protective responses that prevent colonization and invasion by pathogens. On the other hand, these bacteria can directly inhibit the growth of respiratory pathogens by producing antimicrobial products/signals and competing for nutrients and adhesion sites.
invasins
Pathogens may overcome these defences by the production of invasins (proteins associated with the penetration of bacteria into mammalian cells),
Hyaluronidase: Dissolves hyaluronic acid which holds connective tissue cells together
Collagenase: Breaks down collagen in muscle
Kinase: Dissolves blood clots
Phospholipases: Break down phospholipids in cell membranes
Hyaluronidase
: Dissolves hyaluronic acid which holds connective tissue cells together
Collagenase
: Breaks down collagen in muscle
Kinase
: Dissolves blood clots
Phospholipases
: Break down phospholipids in cell membranes
mucous membranes
Made up of epithelial layer and underlying connective tissue layer
• Secretes fluid, viscous glycoprotein (mucus)
• Prevents tracts from drying out (barrier)
• Traps potential pathogens
Lysozyme
in perspiration, tears, saliva, nasal secretions and urine destroys bacterial cell walls
IgA
prevents attachment of microbes preventing penetration of mucous membranes
Sebum
Lowers PH of skin inhibiting growth of pathogenic bacteria and fungi
Bacterial IgA proteases
Immunoglobulin A protease degrades IgA, allowing the organism to adhere to mucous membranes
Neutrophils
(polymorphonuclear leukocytes) active in initial stages of infection – enter infected tissues
Basophils
important in inflammation and allergic responses
Eosinophils
mainly act against parasites – numbers increase upon parasitic worm infection/hypersensitivity reactions
Monocytes
only actively phagocytic once they have entered tissues and matured into macrophages
Granules of NK cells release perforins and granzymes
– kills infected cells & releases microbes for destruction by phagocytes; active against tumour cells
Leukocytosis
Increasedtotalno.WBCinmostinfections;especially bacterial infection
• Duringactivestageofinfectionnumbersmight increase 2 – 4-fold
• Meningitis, infectious mononucleosis, pneumococcal pneumonia & gonorrhea
• Alsooccursinautoimmunedisease(RA),leukemia& in drug toxicity
Leukopenia
DecreasedWBCcountfromimpairedWBC production or increased sensitivity of cell membranes to complement
• Salmonellosis,someviralandrickettsialinfections
• Septicemia – extremely severe bacterial infection
• Alsooccursinautoimmunedisease(lupus), lymphoma, radiation therapy, anticancer drugs, antibiotics & diuretics
Leukocidins
cytotoxin that destroys both neutrophilic leukocytes and macrophages.
Humoral
Antibody-mediated response Extracellular fluids B cells Fast response upon detection Act on Extracellular pathogens Antibody-mediated destruction or neutralization MHC class II proteins
Cell Mediated
T cell-mediated response Location of antigen-presenting tissue T cells Slow response Acts on Intracellular pathogens, cancer cells Cell lysis and programmed death MHC class I proteins
Adaptive immune response - evasion
Concealment of antigens from the host:
• Staying inside host cells without displaying antigens (e.g. latent bovine herpesvirus)
• Infecting ‘privileged sites’ (e.g. microbes that colonise the skin, intestinal lumen, CNS, host cell DNA (retroviruses),
etc.)
Antigenic variation
• During the course of infection in a given individual (e.g. gene switching in brucellosis)
• During spread through the host population, e.g:
- ‘antigenic drift’ as influenza spreads through a community
- ‘genetic shift’ in influenza A virus as human and avian virus strains recombine
Immunosuppression:
Direct action on immune cells (e.g. paramyxovirus (cattle plague) on T cells) or release of immunosuppressive molecules
Cause a rapid ‘hit and run’ infection (e.g. rhinoviruses): invade, replicate and be passed on faster than immune system can respond
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What is another name for humoral immunity?
Antibody mediated immunity
After production in bone marrow, where do B cells mature?
Spleen
- Provide on example of a secondary lymphoid organ where mature B cells will be found?
Lymph nodes, spleen, lymph node nodules
- What feature of antibodies provide their uniqueness for binding with a specific pathogen?
Variable region
- What feature of antibodies distinguishes the major antibody classes?
Constant region
- What is the role of MHC-II proteins on the surface of B-cells?
Presentation of pathogen
- What is the role of follicular T-helper cells?
Bind to antigens on B cells and activate B cells
- What type of cells produce large quantities of antibodies?
Plasma cell
- What is antibody class switching?
When activated B cells switch from igM class to another class
- What is the purpose of the antigen-binding test that takes place in the B-cell germinal centre?
To select and preserve cells with the highest affinity for the antigen to then go on and become memory B cells
Compound light microscope
Compound – consists of two lens systems
Light – uses beam of light to view specimens
Light path of a microscope:
• The optimal set up for a light microscope is referred to as ‘Kohler
illumination’.
• In this case the iris diaphragm of the lamp, the specimen and the primary
image are simultaneously in focus.
• The objective forms a magnified primary image of the specimen in the
image plane, which is viewed and further magnified by the eyepiece.
Bacterial smears Blood smear Histology slides Swabs
Fine needle aspirates
Dark-field microscope
Special condenser set-up scatters light causing it to reflect off the specimen at an angle
Results in bright specimen on a dark background
Phase-contrast microscope
Light waves that are diffracted and shifted in phase by the specimen (termed a phase object) can be transformed by phase contrast into amplitude differences that are observable in the eyepieces
Good for observing live organisms as allows visualisation of transparent cells and structures without the use of stains
Ageing
An accumulation of physical changes over time that render organisms more susceptible to disease and death
A progressive loss of physiological integrity, leading to impaired function
Ageing – hair loss
Hair loss/shedding:
• Atrophied hair follicles
Ageing - sarcopenia
Weight loss/muscle loss • Sarcopenia
• Reduction in muscle fibres
• Affects ‘normal’ activity
Ageing – skin conditions
Dry, flaky skin: • Sebaceous glands less productive • Skin dries out and flakes (dandruff)
Ageing - odour
Odour:
• Reduced immune function
• Recurrent secondary skin
infections
Ageing – immune system
Immune function: • Reduces levels of immune cells • Impaired ability to fight infection & target cancer cells 10
Ageing
Ageing – vision loss
Vision loss: • Cataracts
• Iris atrophy
• Retinal degeneration
Ageing – hearing loss
Hearing loss:
• Degeneration of nerve cells
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Ageing – vocal change
Muffled/weak bark:
• Degeneration of nerve
cells in the larynx
Ageing – incontinence
Incontinence: • Weaker anal and urinary sphincters • Changes in hormone levels can also affect urinary sphincter
Ageing - arthritis
Osteoarthritis: • Progressive degeneration of the joint • Inflammatory disorder • Pain and stiffness in joints
Ageing – cognitive disfunction
Cognitive disfunction: • Changes in behaviour • Secondary to age-related degeneration of the brain • Canine cognitive dysfunction rating (CCDR)
Cognitive disfunction: • Changes in behaviour • Secondary to age-related degeneration of the brain • Canine cognitive dysfunction rating (CCDR)
Ageing – cardiac failure
Cardiac failure:
• Dilated cardiomyopathy
• Valvular disease
• Arterial hypertension
Ageing - diabetes
Diabetes mellitus: • Insufficient insulin production • More common in overweight animals
Hallmarks of ageing – genomic instability
DNA is continually being damaged, mutated and altered
The longer an organism is alive, the greater the chances that a DNA change could lead to disease
Hallmarks of ageing - proteostasis
Impaired protein homeostasis. Proteostasis involves mechanisms for the stabilization of correctly folded proteins and the degradation of incorrect or unneeded proteins by the proteasome or the lysosome
Hallmarks of ageing – cellular senescence
“stable arrest of the cell cycle coupled to stereotyped phenotypic changes” The accumulation of senescent cells in aged tissues can affect function and cause inflammation
Stem cell exhaustion
• • •
Decline in the regenerative potential of tissues
One of the ultimate culprits of tissue and organismal aging
Recent promising studies suggest that stem cell rejuvenation may reverse the aging phenotype at the organismal level
Altered intracellular communication
Alterations in communications between cells and tissues can have widespread effects
Pro-inflammatory status (inflammaging) impacts many organ systems
Parallel dysfunction in the immune system can aggravate the ageing status
Leukocidins
: cytotoxin that destroys both neutrophilic leukocytes and macrophages.
fixed macrophages
Some fixed macrophages are resident in tissues and organs
(e.g. Liver (Kupffer’s cells), lungs (alveolarmacrophages), CNS (microglia), spleen (splenic macrophages), bone (osteoclasts), placenta (Hofbauer cells) etc)
pattern recognition molecules (PRMs)
The initiation of innate immune response relies on the recognition of pathogen-associated molecular patterns by pattern recognition molecules (PRMs), including the cellular pattern recognition receptors and extracellular soluble PRMs.
pathogen-associated molecular patterns (PAMPs)
PAMPs activate innate immune responses, protecting the host from infection, by identifying some conserved nonself molecules. Bacterial lipopolysaccharides (LPSs), endotoxins found on the cell membranes of gram-negative bacteria, are considered to be the prototypical class of PAMPs.
damage-associated molecular patterns (DAMPs)
Damage-associated molecular patterns (DAMPs)[1] are molecules within cells that are a component of the innate immune response released from damaged or dying cells due to trauma or an infection by a pathogen.[2] They are also known as danger-associated molecular patterns, danger signals, and alarmin because they serve as a warning sign for the organism to alert it of any damage or infection to its cells.
toll-like receptors in phagocytosis
detect invaders and activate other cells and processes in innate and adaptive immune system
4 steps of phagocytosis
4 main steps
• Chemotaxis & Adherence
• Chemical signals attract phagocytes to microorganisms
• Phagocyte attaches to microbial cell surface – facilitated by interaction of PAMPs with PRRs on phagocyte surface
• Ingestion
• Opsonization: microorganism is coated with serum proteins to facilitate ingestion
• Phagocyte forms pseudopods to engulf the microbe – formation of phagosome
• Digestion
• Phagosome fuses with a lysosome → phagolysosome where microbe is digested
• Discharge
• Residual body discharges indigestible material from the cell
Various anti-phagocytic mechanisms have evolved to avoid phagocytic killing mechanisms including:
Eluding contact (capsule) Inhibiting or killing the phagocyte (e.g. organism releases toxin) Protection against intracellular death, e.g. - resistance to killing (e.g. staphylococci produce antioxidants) - inhibition of phagolysosome fusion (e.g. Mycobacterium tuberculosis); - escape into the host cell cytoplasm (e.g. leishmaniasis)
Helminths
Multicellularmetazoanparasites
• Requires antibody-dependent cellular cytotoxicity (ADCC)
• FcreceptorsonMo,Eosandneutrophils interact with antibodies coating helminth
• Stimulatesreleaseoftoxic chemicals/proteins
inflammation
Four main signs and symptoms:
• Redness
• Swelling (oedema)
• Pain
• Heat
Three main functions:
• To destroy injurious agent and to remove it/its by-products from body
• To limit its effects on the body by confining/walling off the agent
• To repair and replace tissue damaged by the injurious agent
- Vasodilation & increased permeability of blood vessels
- Phagocyte migration & phagocytosis
- Tissue repair
What are the Chemical signals released by damaged cells, pathogens and activated macrophages cause nearby capillaries to widen and become more permeable
Chemokines
• Cytokines
• Histamines
• Prostaglandins • Leukotrienes
Increasing the permeability of capillaries helps as it:
Increased permeability allows defensive substances in blood to enter injured area:
• Fluid (oedema)
• Antimicrobial proteins
• Clotting elements
Vasodilation also results in redness and heat
Glucocorticoids
Anti-inflammatorymedication
• Suppresscertaincomponentsof the immune system
Fever
systemic response of body to injury
Most frequent cause of fever is infection by bacteria & viruses
Inflammation
local response of body to injury
fever
Complications
- Tachycardia – particularly if any underlying cardiopulmonary disease
- ↑ metabolic rate → acidosis
- Dehydration
- Electrolyte imbalance
- Seizures
- Delirium & coma
- Can be fatal
The compliment system
The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen’s cell membrane. It is part of the innate immune system,[1] which is not adaptable and does not change during an individual’s lifetime. The complement system can, however, be recruited and brought into action by antibodies generated by the adaptive immune system.
Interferons
Interferons are proteins that are part of your natural defenses. They tell your immune system that germs or cancer cells are in your body. And they trigger killer immune cells to fight those invaders. Interferons got their name because they “interfere” with viruses and keep them from multiplying
Antimicrobial peptides
Antimicrobial peptides (AMPs) are a class of small peptides that widely exist in nature and they are an important part of the innate immune system of different organisms. AMPs have a wide range of inhibitory effects against bacteria, fungi, parasites and viruses.
Dominant allele
an allele that produces the same phenotype whether its paired allele is identical or different.
Recessive allele
only expressed if the individual has two copies and does not have the dominant allele of that gene.
Heterozygote
an individual having two different alleles of a particular gene or genes, and so giving rise to varying offspring.
Homozygote
an individual having two identical alleles of a particular gene or genes and so breeding true for the corresponding characteristic.
Autosomes
An autosome is any of the numbered chromosomes, as opposed to the sex chromosomes.
Sex chromosomes
A sex chromosome is a type of chromosome that participates in sex determination. Humans and most other mammals have two sex chromosomes, the X and the Y
Mutation
A mutation is a change in a DNA sequence. Mutations can result from DNA copying mistakes made during cell division, exposure to ionizing radiation, exposure to chemicals called mutagens, or infection by viruses.
Differential regions
Parts of a chromosome that havenocounterpart on the other sex chromosome
• Genesfoundindifferentialregionshow ‘sex-linked’ inheritance patterns
Genetic linkage
Gene loci that are closer together are less likely to be separated onto different chromatids during crossing over
Liability (in the context of genetic disease)
the combined effect of all factors (environmental and genetic), that render an animal more or less likely to develop that disorder
Immunodiagnostics
, Diagnostic tests that use antibodies
Tests either:
• Detect antibodies in a sample OR
• Detect antigens in a sample using antibodies
What is an Antigen (Ag) ?
- Specific portion of pathogen
* Protein found on surface of pathogen • Non-self
What is an Antibody (Ab) ?
- Self
- Protein
- Immunoglobulins
- Designed to “fit” onto specific Ags and so neutralise them
- Specific binding sites
Ig molecules bind specifically to an antigen and eliminate it
For infectious diseases, can test for one of two factors:
Presence of infection
• Looking for pathogen / antigen
Evidence of exposure
• For diseases where antibodies are created
Immunoassays
Immunoassays test for or measure: • Presence of antigen • Presence of specific antibodies • Levels / quantities of antibody to determine level of protection, stage of disease (getting worse or better)
What is required of a test?
Accuracy Repeatability Reliability Quality control
Practicality?
Examples of Immunoassays
Precipitation
Agglutination with latex beads Radio-immunoassays
Agar Gel Immunodiffusion (AGID) Complement Fixation (CF)
Precipitation
Precipitation reactions are based on the interaction of antibodies and antigens. They are based on two soluble reactants that come together to make one insoluble product, the precipitate. These reactions depend on the formation of lattices (cross-links) when antigen and antibody exist in optimal proportions.
Binding of antibodies to the antigen forms precipitate
Agar Gel Immunodiffusion
An antigen and an antibody are placed in separate wells of an agar gel
Antigen and antibodies diffuse towards each other
A thin white line is formed due to the precipitation of antigen/antibody complex
Agglutination
addition to causing precipitation of soluble molecules and flocculation of molecules in suspension, antibodies can also clump together cells or particles (e.g., antigen-coated latex beads) in a process called agglutination . Agglutination can be used as an indicator of the presence of antibodies against bacteria or red blood cells.
Complement Fixation
The antibody from the patient serum and the antigen are mixed with fresh complement. Sensitized sheep cells are then added. When the patient antibody is absent, the complement will be able to bind to the antibody-coated sheep cells and cause hemolysis. But when the antibody is present, the antigen-antibody complex binds to the complement, and therefore, no hemolysis will occur. When there is no hemolysis, it indicates a positive reaction.
Enzyme Linked Immunosorbent Assays
2 types of ELISA:
• Direct test - Antibodies used to test for antigen
• Indirect test – Antigens used to test for antibody Can test for:
• Bacteria or bacterial toxins
• Viruses
• Protozoa
• Ab to any of these or Ab to parasites, yeasts,
Direct Elisa
Antibodies used to test for antigen
Indirect Elisa
Antigens used to test for antibody
Immunohistochemistry (IHC)
To detect antigens in cells of a tissue section
Antibodies introduced that bind specifically to the antigens in questions in situ in the tissue sample
Antigen-antibody complex visualized in different way
Immunofluorescense
Radio-immunoassays
The basic principle of radioimmunoassay is competitive binding, where a radioactive antigen (“tracer”) competes with a non-radioactive antigen for a fixed number of antibody or receptor binding sites.
A RIA is a very sensitive in vitro assay technique used to measure concentrations of substances, usually measuring antigen concentrations (for example, hormone levels in blood) by use of antibodies.
Nucleic acids can be detected by
staining and visualisation through gel electrophoresis (and other methods)
The only way to know if a particular sequence of DNA (a gene) is present is to selectively amplify it
Polymerase chain reaction (PCR)
- Uses oligonucleotide primers to amplify region of interest (gene)
- Cycles of heating and cooling drives each step
- Millions of copies can be produced in minutes
- Number of copies provides information on presence and/or amount of starting material
PCR - denaturation
High temperature breaks hydrogen bonds holding base pairs together
‘Melts’ double-stranded DNA revealing bases in specific order
Fun fact! The polymerase enzymes needed for this procedure were identified in thermophilic bacteria so they could cope with the high temperatures
PCR - annealing
• At cooler temperatures, complementary bases can bind
• Oligonucleotide primers ‘match’ small regions of the target
area (gene of interest)
• They bind to the matching areas (anneal)
Primers must be designed so that one matches the sense strand and the other matches the antisense strand
PCR – extension/elongation
• Temperature raised to approximately 74°C
• Synthesis of new complementary DNA strand from 3’ end
of primer
Only regions where primers bound will be amplified/copied. So it’s really important that they only match the region we’re interested in
PCR – cycling
- In one cycle (denaturation; annealing; extension) we have gone from one copy to two
- Cycle is repeated multiple times and product number increases exponentially
- Average PCR run is 40 cycles
The amount and size of the PCR product can be visualised using
staining and gel electrophoresis
This visually confirms if our pathogen / gene of interest / strain is present
Known as semi-quantitative PCR
qPCR
method by which the amount of the PCR product can be determined, in real-time, and is very useful for investigating gene expression.
does not rely on any downstream analysis such as electrophoresis or densitometry and is extremely versatile, enabling multiple PCR targets to be assessed simultaneously
fluorescence is measured after each cycle and the intensity of the fluorescent signal reflects the momentary amount of DNA amplicons in the sample at that specific time. In initial cycles the fluorescence is too low to be distinguishable from the background. However, the point at which the fluorescence intensity increases above the detectable level corresponds proportionally to the initial number of template DNA molecules in the sample. This point is called the quantification cycle
What are the four distinct phases within the qPCR curve?
Lag
Exponential
Linear and plateau
Reverse transcriptase PCR (RT-PCR)
Uses reverse-transcriptase enzyme to produce double stranded DNA from RNA
• This provides template for normal PCR
• Can also be incorporated into qPCR = RT-qPCR
The Lawrence Livermore Microbial Detection Array (LLMDA)
Livermore scientists analyzed the genetic code of every microbe that has been sequenced (about 6,000 species and strains in all) and then selected the roughly 360,000 most important genetic markers.
In one microarray configuration, 360,000 probes—short stretches of DNA or RNA that complement the isolated genetic markers—are arrayed in a microscopic square grid on a 2.5- by 7.5-centimeter glass slide.
When a fluorescently labeled fluid sample containing the genetic material of microbes contacts the microarray’s probes, only the squares with DNA or RNA unique to a particular organism are activated.
The activated squares produce a fluorescent pattern, from which species present in the sample are identified.
In this way, multiple pathogens are detected simultaneously, with typical processing times of less than 24 hours.
The current-generation LLMDA can identify 3,111 viruses, 1,967 bacteria, 94 protozoa, 136 fungi, and 126 archaea (primitive bacteria).
A good quality clinical specimen should:
- Be collected before the start of antibiotics (where possible)
- Be representative of the infection site
- Be collected in a sterile manner
- Transported properly and quickly
Microscopy
Stained preparations alow you to see
Morphology
- Size
- Shape
- Arrangement
- Staining affinity - Spores
- Capsule
Microscopy Unstained preproductions allow you to see
motility
Simple staining
involves directly staining the bacterial cell with a positively charged dye in order to see bacterial detail, in contrast to negative staining where the bacteria remain unstained against a dark background
Differential staining
Differential Staining is a staining process which uses more than one chemical stain. Using multiple stains can better differentiate between different microorganisms or structures/cellular components of a single organism. … One commonly recognizable use of differential staining is the Gram stain.
Special staining
“Special stains” are processes that generally employ a dye or chemical that has an affinity for the particular tissue component that is to be demonstrated. They allow the presence/or absence of certain cell types, structures and/or microorganisms to be viewed microscopically.
gram stains
Gram stain or Gram staining, also called Gram’s method, is a method of staining used to distinguish and classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria
Gram staining differentiates bacteria by the chemical and physical properties of their cell walls. Gram-positive cells have a thick layer of peptidoglycan in the cell wall that retains the primary stain, crystal violet. Gram-negative cells have a thinner peptidoglycan layer that allows the crystal violet to wash out on addition of ethanol. They are stained pink or red by the counterstain,[2] commonly safranin or fuchsine. Lugol’s iodine solution is always added after addition of crystal violet to strengthen the bonds of the stain with the cell membrane.
Ziehl-Neelsen stain
Differential stain to distinguish between acid fast and non acid fast cells
Initially, carbol fuchsin stains every cell. When they are de-stained with acid-alcohol, only non-acid-fast bacteria get de-stained since they do not have a thick, waxy lipid layer like acid-fast bacteria. When counter stain is applied, non-acid-fast bacteria pick it up and become blue (methylene blue) or green (malachite green) when viewed under the microscope. Acid-fast bacteria retain carbol fuchsin so they appear red.
Differential culture media
Differential media contain compounds that allow groups of microorganisms to be visually distinguished by the appearance of the colony or the surrounding media, usually on the basis of some biochemical difference between the two groups.
Biochemical tests – oxidative-fermantative
The oxidative-fermentative test determines if certain gram-negative rods metabolize glucose by fermentation or aerobic respiration (oxidatively). During the anaerobic process of fermentation, pyruvate is converted to a variety of mixed acids depending on the type of fermentation. The high concentration of acid produced during fermentation will turn the bromthymol blue indicator in OF media from green to yellow in the presence or absence of oxygen .
Biochemical tests – catalase test
The catalase test is primarily used for gram positive bacteria and can be utilized to distinguish Staphylococcus spp.
and Micrococcus spp., which are catalase positive from Streptococcus spp.
and Enterococcus spp., respectively, which are catalase negative
The presence of the catalase enzyme can be demonstrated by adding hydrogen peroxide to the bacterial inoculum, which results in the rapid liberation of oxygen bubbles. The lack of enzyme is demonstrated by the absence of such bubbles.
Citrate test
Some bacteria can utilize citrate as the only carbon source and the citrate test shows if the actual bacterium has this capability.
Positive test result: growth in citrate medium or growth with colour change to blue in Simmon’s citrate tube.
Negative test result: no growth in citrate medium eller growth but no colour change (still green colour) in Simmon’s citrate tube.
Use
The citrate test is used to distinguish between, among others Citrobacter freundii and Escherichia coli.
Coagulase test
Some bacteria produce coagulase, which is an enzyme that converts fibrinogen to fibrin, which means that it can coagulate plasma. The ability to produce coagulase is assumed to be associated to the virulence of staphylococci. The test is used to distinguish between coagulase positive and coagulase negative staphylococci.
Positive reaction if the plasma coagulates and the coagulate is stable. It must not be dissolved upon stirring.
Negative reaction if the plasma does not coagulate or if the coagulate is dissolved again upon stirring.
The coagulase test is used to distinguish between Staphylococcus aureus from coagulase negative Staphylococcus spp
DNase test
Many bacteria have enzymes that break down nucleic acids. The bacteria can then use the resulting nucleotides to build up their own nucleic acids. DNase is such an enzyme, which thus hydrolyzes DNA. Existence of DNase is characteristic for certain species or strains of bacteria and can be used for typing.
Presence of DNase can be determined by cultivation on an agar plate, which contains DNA. If the bacterium has DNase and if the bacteria are allowed to grow over night, the DNA will be hydrolyzed into the constituting nucleotides. Diluted hydrochloric acid (HCl) is then poured onto the plate and there will be a clear zone close to the colonies or the streak, because individual nucleotides are soluble in diluted HCl, but not DNA, which precipitates in the rest of the plate.
Use
The test is useful to distinguish between:
Serratia spp. and Enterobacter spp.
Staphylococcus aureus (most strains are coagulase positive) and coagulase negative Staphylococcus spp.
Moraxella catarrhalis and Neisseria spp.
Hippurate test
Some bacteria can hydrolyze hippurate to the amino acid glycine and benzoate by means of the enzyme hippuricase. Glycine can be detected with ninhydrin (2,2-Dihydroxyindane-1,3-dione), which reacts with free amino groups (-NH2) and a blue product is formed.
Positive test resultat: Deep blue colour.
Negative test result: Pale blue colour.
Use
The hippurate test is primarely used to distinguish between Campylobacter jejuni (hip+) and Campylobacter coli (hip-) and to distinguish between different streptococci (see figure).The test is also used, in combination with other methods, to type Brachyspira spp.
Hydrogen sulfide production test
Some bacteria can metabilize certain sulfur containing compounds under production of hydrogen sulfide (H2S). Hydrogen sulfide is a toxic, flamable and badly smelling gas (smells like rotten eggs). If soluble iron or lead salts (for instance ferric citrate) is used in a so-called H2S-medium, which should also contain sodium thiosulfate (Na2S2O3), they can react with H2S, if present, under formation of black insoluble iron and lead sulfide, respectively.
Positive test result: a black precipitate in the medium.
Negative test result: no precipitate in the medium.
Use
The test can be used for differentiation of, among other bacteria, certain Campylobacter spp.
Kovac´s reagent
Positive test result: The indole reagent change colour to cerise red.
Negative test result: The indole reagent remains pale yellow.
Use
Confirmation of suspected E. coli-strains. Typing (species determination) of Brachyspira spp. in combination with other tests. Kovac’s indole reagent is more sensitive than the indole spot reagent, but it is not recommended for use with anaerobic bacteria. The indole spot reagen is suitable for both aerobic and anaerobe use.
Lecithinase test
Many bacteria have enzymes which can break down lipids, so-called lipases. Lecithinase, which is also called phospholipase C, is such an enzyme that splits the phospholipid lecithin (= e.g. phosphatidylcholine). Phospholipids, which are charged are usually soluble in water, but one of the products which is formed by the splitting, namely a diglyceride, is not charged and it has two long hydrocarbon chains. It is, therefore, unsoluble in water and this is utilized in the lecithinase test, where bacteria are cultivated on egg yolk agar. Egg yolk contains a lot of lecithin.
Method
Apply the bacteria in the form of a streak onto the egg yolk agar.
Read the plate after 24 h.
Positive test result: Precipitation around the streak of bacteria.
Negative test result: No precipitation.
Can among other things be used to differentiate between certain species within the genus Bacillus.
Mixed acid fermentation test
Some bacteria can ferment glucose to a mixture of the following organic acids: formic acid, acetic acid and lactic acid. This is called mixed acid fermentation and it causes highly decreased pH in the medium. Mixed acid fermentation can, therefore, be detected by addition of the pH indicator methyl red (MR). The test method is sometimes called the MR test.
Positive test result: red colour change
Negative test result: no colour change.
Use
Some members of the family Enterobacteriaceae have mixed acid fermentation (see the respective bacterial page), which can be used to differentiate these bacteria.
Oxidase test
Bacteria, which have aerobic respiration, often have cytochrome c and a cytochrome c oxidase. The presence of these components can in combination with other methods be used for typing. A commersial test, which contains an artificial electron acceptor (N, N, N’, N’-tetramethyl-p-phenylenediamine, see Fig. 1), is often used. This artificial electron acceptor change colour depending upon redox state.
Positive test resultat: Dark blue-purple colour change within 10-30 sec.
Negative test resultat: No colour change or colour change after more than 30 sec.
The oxidase test is used for identification of gram negative bacteria. For instance to identify members of the family Enterobacteriaceae, which are oxidase negative, except members of the genus Plesiomonas (oxidase positive). Members of the family Pseudomonadaceae, and the genera Aeromonas and Campylobacter are oxidase positive.
Potassium hydroxide test
The purpose of the potassium hydroxide test (KOH test) is to identify gram negative bacteria. KOH dissolves the thin layer of peptidoglycan of the cell walls of gram negative bacteria, but does not affect gram positive cell walls. Disintergration of gram negative cell walls lyses the cell and release its contents, including the DNA. The DNA will make the solution very viscous and the solution will stick to the plastic loop when touched. Gram positive bacteria will not be affected by KOH, because they have thicker peptidoglycan layer in the cell wall. Thus, the cells will not be lysed, the DNA not released and no viscosity will be observed.
Positive results: The solution with the bacteria (gram negative) will be viscous
Negative results: The solution with the bacteria (gram positive) will not be viscous
Use
The purpose of the KOH test is to quickly distinguish between gram negative and gram positive bacteria as a complement to Gram staining. The test is not useful for anaerobic bacteria.
Urease test
Some bacteria have the enzyme urease, which in the presence of H2O converts urea (=carbamide) to NH3 (ammonia) and CO2 (carbondioxide), which forms ammonium carbonate in the presence of water.
Positive test result: colour change to pink.
Negative test result: no colour change.
Klebsiella spp. and Enterobacter spp. has the capacity to perform butanediole fermentation in contrast to Escherichia coli, Salmonella spp. and Shigella spp.
refractometer
instrument that measures the refractive index of a liquid. The more particles there are in a liquid the more a beam of light will be bent (refracted) as it passes from one medium to another e.g. from air to urine. The result is the formation of a shadow line between the illuminated and dark areas. The result is read from where this shadow line crosses the scale on the refractometer
Veterinary clinical refractometers typically have two or three scales (figure 3). The scale used to measure specific gravity is normally found on the righthand side and is typically labelled as U.G. (urine gravity) or S.G. (specific gravity) with a range of 1.000-1.030 or 1.000-1.040
The scale on the left is for serum protein (S.P.). It is used to measure the total protein levels present in a serum or plasma sample. Its units are typically g/dl (g/100ml). These units may also be printed on the lid of the refractometer case.
3
The central scale is the refractive index scale (nD or ND). It can be used with appropriate conversion charts to measure the concentration of many other solutions. It is not present on all clinical refractometers.
Specific gravity
The specific gravity of a substance refers to its density divided by (or relative to) the density of water. This is why specific gravity has no units, as it is based on the ratio of one density to
another, so the units cancel each other out. The specific gravity of pure (distilled) water is therefore expressed simply as 1.000
In veterinary medicine we frequently want to know the specific gravity (S.G.) of liquids such as urine or colostrum because this information can be clinically useful.
Urine typically has a S.G. in the range of 1.003 to 1.035. This means it is slightly denser than water. This makes sense as we know that urine consists of a mixture of excess body water and waste products of metabolism such as urea and creatinine, along with some crystals etc. Even very dilute urine contains some of these waste products so it will always have a S.G. >1.000. Very dilute urine is often seen in animals suffering from polyuria & polydipsia (PU/PD).
Tips for accurate urine S.G. results:
• If the sample was refrigerated allow it to come to room temperature before testing.
• Ensure that you are using the correct scale(!).
• Ensure that distilled water is reading 1.000 on the correct scale before testing.
• Ensure the urine sample is well mixed before testing it.
Increased urine S.G. is associated with
dehydration, shock, acute renal failure, reduced water intake and/or increased fluid loss e.g. vomiting, panting, sweating or diarrhoea, as well as increased excretion of urine solutes (such as glucose in cases of undiagnosed or poorly controlled diabetes mellitus).
Reduced urine S.G. is associated with
increased fluid intake (polydipsia), overzealous administration of fluid therapy. Diseases that reduce the ability of the kidney to reabsorb water (pyometra, diabetes insipidus, some liver conditions, kidney disease) will result in low S.G., as will the administration of diuretic drugs.
Isothenuria
occurs when the urine S.G. is the same as that of the glomerular filtrate (1.008-1.012). This indicates renal disease severe enough to result in the loss of the ability to concentrate or dilute the urine e.g. chronic renal failure. Even if these animals are deprived of water, their urine S.G. will not rise. Animals with less severe renal disease may have moderate but persistent dehydration and a urine S.G. that remains slightly higher than isothenuria (1.015-1.020).
California mastitis test
The California Mastitis Test (CMT) is a cow side test to estimate the somatic cell count of milk. It is a diagnostic tool to aid in the quick diagnosis of mastitis in dairy cows, and for an udder health management program.
The CMT is performed to;
• Detect the presence of subclinical infections at the beginning of or during lactation as part of an udder health management program.
• Additional diagnostics for cows with clinical signs of Mastitis.
The CMT will only trigger a visible reaction with a concentration of 400,000 cells/ml or more Observing results:
Mastitic milk tends to gel when tested by the CMT procedure. The degree of gelling indicates the presence and severity of mastitis. The change in colour indicates the pH variation of the milk and therefore, the level of inflammation
When infection occurs, white blood cells, or leukocytes, gather to engulf bacteria and stop the spread of infection. High leukocyte counts in milk strongly indicate mastitis-causing bacteria are present. The
CMT reagent, when added to milk, disrupts cell membranes allowing the DNA in the cells to react with the reagent and form a gel. The greater the mastitis infection, the more leukocytes present and the more gel-like substance that forms
Urinary dipsticks
The chemical examination of urine is usually performed by the use of reagent strips. These are multiparameter strips that contain a number of pads, each designed to test for a specific urine constituent:
Glucose
Bilirubin
Ketones
Blood
pH
Protein
Urobilinogen
Nitrite
Leukocytes
glucosuria
The term used to describe glucose in the urine is glucosuria. The reagent strip method for detecting glucose is specific for glucose, meaning no other sugar will cause a positive result. Possible causes of false positives with the reagent strips are contamination with hydrogen peroxide, as well as other strong oxidizing agents, such as chlorine. False negatives (or decreased values) can be seen in urine samples preserved with formalin.
bilirubinuria
When bilirubin is present in the urine, the term “bilirubinuria” is used. Bilirubin is unstable in sunlight or artificial light and should therefore be tested immediately. Delaying testing will result in false negative values.
Ketones: urinary dipsticks
There are three ketone bodies that are produced: acetone, acetoacetic acid, and β -hydroxybutyric acid. Most reagent strips are sensitive to acetoacetic acid, less sensitive to acetone, and do not detect β -hydroxybutyric acid. The presence of ketone bodies in the urine, or ketonuria, is often accompanied by a fruity odor
Blood urinary dipsticks
Reagent strips have the ability to detect intact RBC (hematuria), free hemoglobin (hemoglobinuria), and myoglobin (myoglobinuria) in a urine sample. The test is quite sensitive, and positive samples may appear normal in color during the physical exam.
pH urinary dipsticks
pH testing through reagent strips offer analysis of the urine’s acidity or alkalinity over a pH range of 5.0– 8.5. Results are read at 0.5 intervals on the pH scale. Care should be taken when using the reagent stick as not to contaminate the pH pad with the acidic buffer contained within the neighbouring protein pad.
Protein urinary dipsticks
When protein is present in the urine, the term proteinuria is used. Reagent strips are not specific for any particular protein. They primarily detect albumin and are less sensitive for globulins and mucoproteins. False negatives may occur due to the low concentration of protein contained within the sample therefore the concentration may fall below the sensitivity level of the reagent strip.
Urobilinogen urinary dipsticks
When testing for urobilinogen, the same light-sensitivity precautions used for bilirubin should be taken. Other false negatives can result from the use of formalin as a preservative.
Nitrite urinary dipsticks
Nitrites are products formed from nitrates by the actions of certain species of bacteria. Because of this, the presence of nitrites can suggest a bacterial infection, but the absence of nitrites should not rule it out. The reagent strips are specific for nitrites only.
Leukocytes urinary dipsticks
Leukocytes present in the urine are termed pyuria. The reagent strip method for detecting leukocytes relies on the detection of a leukocyte esterase enzyme. The presence or absence of leukocytes should always be confirmed with a sediment examination.
Microscope urinalysis
Sediment examination is the final step of a complete urinalysis. A sediment exam not only allows you to visualize structures such as cells, crystals, and casts, but it also serves to confirm suspected findings during the physical and chemical examinations previously conducted. As with all phases of testing, fresh urine is preferred, but appropriate preservation, typically refrigeration, is acceptable, especially when a delay in processing is anticipated.
Characteristics of a good smear
- Covers 3/4 of the slide
- Symmetrical, bullet-shape
- No tails or ridges
- Microscopically: should have an even distribution of cells
Blood smear stains
After a smear has completely air dried, it must be stained to identify cells and their characteristics. A Romanowsky-type stain, Wright’s stain, is used in hematology to stain blood smears. A commercial stain that is commonly used is Diff-Quick, which is a modified Wright’s stain (see Figure 2.9). The stain consists of three solutions that fix and stain various components of the cells. The first solution, a fixative, consists of 95% methanol. The second solution, eosin, has an acidic pH and stains cell cytoplasms and eosinophilic granules. The third solution, methylene blue, has an alkaline pH and stains the nuclei of the cells. The slide exposure time to each solution varies slightly depending upon the desired result or sample being stained. Typically, dipping a slide into each solution five times for one second each time dip will give adequate staining. This can be adjusted to alter the appearance of cells. It is important to rinse the slide after the last dip into stain #3. Distilled water is preferred. The now stained smear should be allowed to air dry. Rapid drying, such as a hair dryer or waving the slide, will cause crenation (distortion) of the RBCs.
slide agglutination
Immune-mediated haemolytic anaemia (IMHA) is one of the most common immune-mediated hematologic disorders in dogs and cats.
complement formation against RBCs causes accelerated cell destruction and subsequent anaemia. The anti-RBC antibodies can be either immunoglobulin G or M (IgG or IgM). In IMHA the body actually coats its red blood cells with antibodies and then the red blood cells end up sticking together.
IMHA is a
type II immune reaction, where antibody and/or High levels of anti-RBC antibodies sometimes result in their attachment to more than one cell, causing spontaneous RBC agglutination. Agglutination may be appreciated as red speckles when blood is placed in an EDTA tube or onto a microscope slide.
haematology analyser
Resources on the haematology analyser can be found on the manufacturer’s website here
Haematology analysers are used widely in patient and research settings to count and characterize blood cells for disease detection and monitoring. Basic analysers return a complete blood count (CBC) with a three-part differential white blood cell (WBC) count.
The three main physical technologies used in hematology analyzers are: electrical impedance, flow cytometry, and fluorescent flow cytometry. These are used in combination with chemical reagents that lyse or alter blood cells to extend the measurable parameters. For example, electrical impedance can differentiate red blood cells (RBCs), WBCs, and platelets by volume. Adding a nucleating agent that shrinks lymphocytes more than other WBCs makes it possible to differentiate lymphocytes by volume.
Electrical impendence
The traditional method for counting cells is electrical impedance, also known as the Coulter Principle.
It is used in almost every haematology analyser. Whole blood is passed between two electrodes through an aperture so narrow that only one cell can pass through at a time. The impedance changes as a cell passes through. The change in impedance is proportional to cell volume, resulting in a cell count and measure of volume. Impedance analysis returns CBCs and three-part WBC differentials (granulocytes, lymphocytes, and monocytes) but cannot distinguish between the similarly sized granular leukocytes: eosinophils, basophils, and neutrophils. Counting rates of up to 10,000 cells per second can be achieved and a typical impedance analysis can be carried out in less than a minute.
Flow cytometry
Laser flow cytometry is more expensive than impedance analysis, due to the requirement for expensive reagents, but returns detailed information about the morphology of blood cells. It is an excellent method for determining five-part WBC differentials. A single-cell stream passes through a
laser beam. The absorbance is measured, and the scattered light is measured at multiple angles to
13
determine the cell’s granularity, diameter, and inner complexity. These are the same cell morphology characteristics that can be determined manually from a slide.
Fluorescent flow cytometry
Adding fluorescent reagents extends the use of flow cytometry to measure specific cell populations. Fluorescent dyes reveal the nucleus-plasma ratio of each stained cell. It is useful for the analysis of platelets, nucleated RBCs, and reticulocytes.
refractometer
instrument that measures the refractive index of a liquid. The more particles there are in a liquid the more a beam of light will be bent (refracted) as it passes from one medium to another e.g. from air to urine. The result is the formation of a shadow line between the illuminated and dark areas. The result is read from where this shadow line crosses the scale on the refractometer
Veterinary clinical refractometers typically have two or three scales (figure 3). The scale used to measure specific gravity is normally found on the righthand side and is typically labelled as U.G. (urine gravity) or S.G. (specific gravity) with a range of 1.000-1.030 or 1.000-1.040
The scale on the left is for serum protein (S.P.). It is used to measure the total protein levels present in a serum or plasma sample. Its units are typically g/dl (g/100ml). These units may also be printed on the lid of the refractometer case.
3
The central scale is the refractive index scale (nD or ND). It can be used with appropriate conversion charts to measure the concentration of many other solutions. It is not present on all clinical refractometers.
Specific gravity
The specific gravity of a substance refers to its density divided by (or relative to) the density of water. This is why specific gravity has no units, as it is based on the ratio of one density to
another, so the units cancel each other out. The specific gravity of pure (distilled) water is therefore expressed simply as 1.000
In veterinary medicine we frequently want to know the specific gravity (S.G.) of liquids such as urine or colostrum because this information can be clinically useful.
Urine typically has a S.G. in the range of 1.003 to 1.035. This means it is slightly denser than water. This makes sense as we know that urine consists of a mixture of excess body water and waste products of metabolism such as urea and creatinine, along with some crystals etc. Even very dilute urine contains some of these waste products so it will always have a S.G. >1.000. Very dilute urine is often seen in animals suffering from polyuria & polydipsia (PU/PD).
Tips for accurate urine S.G. results:
• If the sample was refrigerated allow it to come to room temperature before testing.
• Ensure that you are using the correct scale(!).
• Ensure that distilled water is reading 1.000 on the correct scale before testing.
• Ensure the urine sample is well mixed before testing it.
Increased urine S.G. is associated with
dehydration, shock, acute renal failure, reduced water intake and/or increased fluid loss e.g. vomiting, panting, sweating or diarrhoea, as well as increased excretion of urine solutes (such as glucose in cases of undiagnosed or poorly controlled diabetes mellitus).
Reduced urine S.G. is associated with
increased fluid intake (polydipsia), overzealous administration of fluid therapy. Diseases that reduce the ability of the kidney to reabsorb water (pyometra, diabetes insipidus, some liver conditions, kidney disease) will result in low S.G., as will the administration of diuretic drugs.
Isothenuria
occurs when the urine S.G. is the same as that of the glomerular filtrate (1.008-1.012). This indicates renal disease severe enough to result in the loss of the ability to concentrate or dilute the urine e.g. chronic renal failure. Even if these animals are deprived of water, their urine S.G. will not rise. Animals with less severe renal disease may have moderate but persistent dehydration and a urine S.G. that remains slightly higher than isothenuria (1.015-1.020).
California mastitis test
The California Mastitis Test (CMT) is a cow side test to estimate the somatic cell count of milk. It is a diagnostic tool to aid in the quick diagnosis of mastitis in dairy cows, and for an udder health management program.
The CMT is performed to;
• Detect the presence of subclinical infections at the beginning of or during lactation as part of an udder health management program.
• Additional diagnostics for cows with clinical signs of Mastitis.
The CMT will only trigger a visible reaction with a concentration of 400,000 cells/ml or more Observing results:
Mastitic milk tends to gel when tested by the CMT procedure. The degree of gelling indicates the presence and severity of mastitis. The change in colour indicates the pH variation of the milk and therefore, the level of inflammation
When infection occurs, white blood cells, or leukocytes, gather to engulf bacteria and stop the spread of infection. High leukocyte counts in milk strongly indicate mastitis-causing bacteria are present. The
CMT reagent, when added to milk, disrupts cell membranes allowing the DNA in the cells to react with the reagent and form a gel. The greater the mastitis infection, the more leukocytes present and the more gel-like substance that forms
Urinary dipsticks
The chemical examination of urine is usually performed by the use of reagent strips. These are multiparameter strips that contain a number of pads, each designed to test for a specific urine constituent:
Glucose
Bilirubin
Ketones
Blood
pH
Protein
Urobilinogen
Nitrite
Leukocytes
glucosuria
The term used to describe glucose in the urine is glucosuria. The reagent strip method for detecting glucose is specific for glucose, meaning no other sugar will cause a positive result. Possible causes of false positives with the reagent strips are contamination with hydrogen peroxide, as well as other strong oxidizing agents, such as chlorine. False negatives (or decreased values) can be seen in urine samples preserved with formalin.
bilirubinuria
When bilirubin is present in the urine, the term “bilirubinuria” is used. Bilirubin is unstable in sunlight or artificial light and should therefore be tested immediately. Delaying testing will result in false negative values.
Ketones: urinary dipsticks
There are three ketone bodies that are produced: acetone, acetoacetic acid, and β -hydroxybutyric acid. Most reagent strips are sensitive to acetoacetic acid, less sensitive to acetone, and do not detect β -hydroxybutyric acid. The presence of ketone bodies in the urine, or ketonuria, is often accompanied by a fruity odor
Blood urinary dipsticks
Reagent strips have the ability to detect intact RBC (hematuria), free hemoglobin (hemoglobinuria), and myoglobin (myoglobinuria) in a urine sample. The test is quite sensitive, and positive samples may appear normal in color during the physical exam.
pH urinary dipsticks
pH testing through reagent strips offer analysis of the urine’s acidity or alkalinity over a pH range of 5.0– 8.5. Results are read at 0.5 intervals on the pH scale. Care should be taken when using the reagent stick as not to contaminate the pH pad with the acidic buffer contained within the neighbouring protein pad.
Protein urinary dipsticks
When protein is present in the urine, the term proteinuria is used. Reagent strips are not specific for any particular protein. They primarily detect albumin and are less sensitive for globulins and mucoproteins. False negatives may occur due to the low concentration of protein contained within the sample therefore the concentration may fall below the sensitivity level of the reagent strip.
Urobilinogen urinary dipsticks
When testing for urobilinogen, the same light-sensitivity precautions used for bilirubin should be taken. Other false negatives can result from the use of formalin as a preservative.
Nitrite urinary dipsticks
Nitrites are products formed from nitrates by the actions of certain species of bacteria. Because of this, the presence of nitrites can suggest a bacterial infection, but the absence of nitrites should not rule it out. The reagent strips are specific for nitrites only.
Leukocytes urinary dipsticks
Leukocytes present in the urine are termed pyuria. The reagent strip method for detecting leukocytes relies on the detection of a leukocyte esterase enzyme. The presence or absence of leukocytes should always be confirmed with a sediment examination.
Microscope urinalysis
Sediment examination is the final step of a complete urinalysis. A sediment exam not only allows you to visualize structures such as cells, crystals, and casts, but it also serves to confirm suspected findings during the physical and chemical examinations previously conducted. As with all phases of testing, fresh urine is preferred, but appropriate preservation, typically refrigeration, is acceptable, especially when a delay in processing is anticipated.
Characteristics of a good smear
- Covers 3/4 of the slide
- Symmetrical, bullet-shape
- No tails or ridges
- Microscopically: should have an even distribution of cells
Blood smear stains
After a smear has completely air dried, it must be stained to identify cells and their characteristics. A Romanowsky-type stain, Wright’s stain, is used in hematology to stain blood smears. A commercial stain that is commonly used is Diff-Quick, which is a modified Wright’s stain (see Figure 2.9). The stain consists of three solutions that fix and stain various components of the cells. The first solution, a fixative, consists of 95% methanol. The second solution, eosin, has an acidic pH and stains cell cytoplasms and eosinophilic granules. The third solution, methylene blue, has an alkaline pH and stains the nuclei of the cells. The slide exposure time to each solution varies slightly depending upon the desired result or sample being stained. Typically, dipping a slide into each solution five times for one second each time dip will give adequate staining. This can be adjusted to alter the appearance of cells. It is important to rinse the slide after the last dip into stain #3. Distilled water is preferred. The now stained smear should be allowed to air dry. Rapid drying, such as a hair dryer or waving the slide, will cause crenation (distortion) of the RBCs.
slide agglutination
Immune-mediated haemolytic anaemia (IMHA) is one of the most common immune-mediated hematologic disorders in dogs and cats.
complement formation against RBCs causes accelerated cell destruction and subsequent anaemia. The anti-RBC antibodies can be either immunoglobulin G or M (IgG or IgM). In IMHA the body actually coats its red blood cells with antibodies and then the red blood cells end up sticking together.
IMHA is a
type II immune reaction, where antibody and/or High levels of anti-RBC antibodies sometimes result in their attachment to more than one cell, causing spontaneous RBC agglutination. Agglutination may be appreciated as red speckles when blood is placed in an EDTA tube or onto a microscope slide.
haematology analyser
Resources on the haematology analyser can be found on the manufacturer’s website here
Haematology analysers are used widely in patient and research settings to count and characterize blood cells for disease detection and monitoring. Basic analysers return a complete blood count (CBC) with a three-part differential white blood cell (WBC) count.
The three main physical technologies used in hematology analyzers are: electrical impedance, flow cytometry, and fluorescent flow cytometry. These are used in combination with chemical reagents that lyse or alter blood cells to extend the measurable parameters. For example, electrical impedance can differentiate red blood cells (RBCs), WBCs, and platelets by volume. Adding a nucleating agent that shrinks lymphocytes more than other WBCs makes it possible to differentiate lymphocytes by volume.
Electrical impendence
The traditional method for counting cells is electrical impedance, also known as the Coulter Principle.
It is used in almost every haematology analyser. Whole blood is passed between two electrodes through an aperture so narrow that only one cell can pass through at a time. The impedance changes as a cell passes through. The change in impedance is proportional to cell volume, resulting in a cell count and measure of volume. Impedance analysis returns CBCs and three-part WBC differentials (granulocytes, lymphocytes, and monocytes) but cannot distinguish between the similarly sized granular leukocytes: eosinophils, basophils, and neutrophils. Counting rates of up to 10,000 cells per second can be achieved and a typical impedance analysis can be carried out in less than a minute.
Flow cytometry
Laser flow cytometry is more expensive than impedance analysis, due to the requirement for expensive reagents, but returns detailed information about the morphology of blood cells. It is an excellent method for determining five-part WBC differentials. A single-cell stream passes through a
laser beam. The absorbance is measured, and the scattered light is measured at multiple angles to
13
determine the cell’s granularity, diameter, and inner complexity. These are the same cell morphology characteristics that can be determined manually from a slide.
Fluorescent flow cytometry
Adding fluorescent reagents extends the use of flow cytometry to measure specific cell populations. Fluorescent dyes reveal the nucleus-plasma ratio of each stained cell. It is useful for the analysis of platelets, nucleated RBCs, and reticulocytes.
polymorphisms
When there are multiple potential versions of a gene that are common in a population they are referred to as polymorphisms
Polymorphisms can be:
• Single nucleotide polymorphisms - differences in a single nucleotide
• Deletions (of large or small amounts of DNA)
• Copy number variation - chromosomal regions that differ in copy number of certain
regions from one to the next
• Microsatellites – tandemly repeated short DNA sequences (also called simple sequence repeats or short tandem repeats) which vary by how many repeats are present
(there are many other types as well!)
Single nucleotide polymorphisms
Single nucleotide polymorphisms (SNPs or ‘snips’) are a prevalent type of polymorphism
Single base-pair differences between individuals in a population
Every genome contains millions of SNPs
and they can be used to identify unique features in individuals (e.g. in a paternity test)
Some SNPs are the cause of inherited genetic disorders as the polymorphism can result in a faulty, inactive or overactive gene product.
Analysis of our patient’s DNA can be done in three main ways:
- Polymerase chain reaction (PCR) – to look at individual SNPs
- DNA microarrays – for analysing collections of known genetic variants
- Whole genome sequencing (WGS) – identifying the exact sequence of every nucleotide in a patients genome to pick out any polymorphisms linked to disease phenotypes (currently cost-prohibitive in veterinary medicine)
Linkage tests (DNA based)
Most DNA tests look for a particular gene that is known to cause a particular condition. Sometimes scientists are unable to find the exact gene, but are able to know approximately where in a dog’s genome it is located. Genes and other genetic markers are often inherited together because they are near one another on the same chromosome. While it may be difficult to identify the exact gene causing a condition, scientists are sometimes able to find sections of DNA that are usually linked to, and inherited alongside, the unknown gene. By identifying these linked genetic markers, breeders are able to know, with considerable confidence, the genetic status of their dogs.
Risk-based DNA tests (incomplete penetrance)
Most DNA tests look for a particular gene that is known to cause a particular condition. For some conditions, certain environmental factors, or other genetic influences can also contribute to whether a dog becomes affected. Having copies of the disease-causing genes will therefore not be a guarantee that the condition will occur. Similarly an absence of these genes will not be a guarantee that the condition will not occur.
These risk-based tests are sometimes not quite as accurate as other DNA tests, but can still be highly accurate and laboratories will often estimate how accurate their test is.
There are several methods available for assessing gastrointestinal samples for the
presence of parasites, which include -
Stained faecal smear – protozoan oocysts and trophozoites
• Passive faecal flotation – helminth eggs
• Centrifugal flotation – protozoan cysts
• Faecal sedimentation – helminth ova (especially trematode ova) • Baermann technique – lungworm larvae in faeces
• Vomit flotation – nematode ova
Blood analysis for endoparasites.
Assessment of blood samples can aid in the detection of certain parasite
species.
• Direct blood examination – heartworm microfilaria • Modified Knott’s test - heartworm microfilaria
• ELISA testing – heartworm antigens and antibodies • Stained blood smear – blood protozoa
Urine Analysis for endoparasites.
• Urine sedimentation – helminth ova
Skin Analysis.
• Skin scrapes/brushings/hair plucks – range of ectoparasites
Gastrointestinal diagnostic methods: Faecal Sampling for parasites
Many parasites pass ova, cysts or larvae in the faeces, which can then be detected by faecal analysis.
• Shedding of larvae and ova is often intermittent, so ideally, samples should be collected over three consecutive days for increased diagnostic sensitivity.
11
• Collection of faecal sample.
• Faecal samples can be collected from the ground
or directly from the rectum.
• From the ground - If the sample is collected from the ground, it must be picked up as soon as it is passed to avoid contamination with free-living nematodes and mites which may confuse diagnosis and obscure the field of view during microscopic examination.
• Directly from the rectum – Using a gloved hand/finger (species dependent) this method achieves a fresh, uncontaminated sample.
• Care must be taken to avoid damaging rectal mucosa.
12
• Storage of sample.
• Once collected, samples should either be examined immediately, or stored at 4°C to
prevent hatching of ova or larval development.
• Hookworm eggs will rapidly develop and hatch if faeces are left at room temperature.
• Ensure that faecal sample fills the container – too much air space encourages parasite eggs to hatch prior to examination.
• Store for no more than 7 days in sterile, airtight and clearly labelled container – if examination is delayed, dilution with 10% formalin stops endoparasite development.
Causes of sample deterioration or inaccurate results
General operator error
Incorrect sample collection technique
Delay between defaecation and examination
Contamination of sample (on collection, in storage or in the lab)
Incorrect handling, storage or sample preservation
Inappropriate package / storage for transport to external lab
Direct faecal smear
Direct smear is a very simple technique and can easily be
performed in practice.
• A small faecal sample (the size of the head of a match) is mixed with a drop of water on a microscope slide and examined with a cover slip under the microscope.
• The addition of a drop of lugol’s iodine will aid in the detection of Giardia cysts, which will be stained yellow.
• Direct smears only analyse very small volumes of faeces, and, as a result, are considered too insensitive for the detection of helminth ova, which are passed in relatively low numbers.
• Lung worm larvae such as Crenosoma vulpis and Angiostrongylus vasorum may be detected, and is useful as an initial screen for these parasites, however the low sensitivity (54% to 61%) for the detection of lungworm by this method means it should not be relied on as a sole test if negative.
Faecal flotation.
- Faecal flotation remains the most common method to detect helminth eggs and protozoan cysts and are commonly used in large and small animal faecal analysis.
- Flotation techniques allow much larger volumes of faeces to be examined by concentrating ova into small volumes of liquid whilst eliminating debris and allowing direct assessment of parasitic ova.
• Principle.
• The principle of faecal flotation is based on the specific gravity (SG) differences of the various parts of a faecal sample, i.e. faeces, ova, cysts and debris.
• The parasite eggs are lighter (i.e. a lower SG) than the flotation solution and so will float to the surface, whereas the heavier faecal matter (i.e. higher SG) sinks rapidly.
• Therefore,theflotationsolutionutilisedmusthaveahigherSGthan the parasite eggs or cysts.
16
- There are several faecal flotation solutions that are commonly used in diagnostic assessment.
- Many of these can be made quickly and easily in practice.
- Solution utilised should be chosen based on health history of animal and the expected findings.
Many different faecal flotation methods are described in the literature, however the Modified McMaster Technique (MMT) is commonly used (see practical sessions for details).
• The McMaster technique uses a counting chamber that has two compartments, each with a grid etched onto the upper surface.
• When filled with a suspension of faeces in flotation fluid, much of the debris will sink while eggs float to the surface where they can easily be seen and counted.
• If a known weight of faeces and a known volume of flotation fluid are used to prepare the suspension, then the number of eggs per gram of faeces can be calculated.
• (The MMT may have diagnostic sensitivities as low as 60% for some roundworm ova such as Toxocara species and has poor sensitivity for tapeworm egg detection, however pooling samples over a three day period will increase sensitivity)
Sodium chloride for fecal flotation
Common helminths, protozoan ova and cysts
Sg: 1.2
Sheather’s solution for fecal flotation
Common helminth, protozoan ova and cysts (particularly Cryptosporidium oocysts)
Sg: 1.2-1.25
Sodium nitrate solution for fecal flotation
Common helminth, protozoan ova and cysts
Sg:1.2-1.33
Zinc sulphate for fecal flotation
Common helminth (particularly Giardia), protozoan ova and cysts (particularly lungworm larvae) Sg:1.18
Magnesium Sulphate solution for fecal flotation
Protozoan ova and cysts
Sg:1.32
Centrifugal flotation technique.(fecal flotation)
- Centrifugal flotation increases effectiveness by spinning down faecal debris, allowing the eggs/cysts to float to the surface.
- Many research papers have demonstrated that correctly carried out centrifugal flotation results in significantly higher faecal egg counts than using flotation techniques alone.
Vomit flotation.
• While not common, it is possible to identify some nematode ova by evaluating
vomit using the same methodology as for faecal flotation.
• Likewise, vomit may also be scrutinized under a microscope to locate parasites common to the stomach.
• Vomit flotation is useful when parasites, such as Physaloptera species or Ollulanus tricuspis, are suspected in dogs and cats.
Faecal Sedimentation
- The majority of trematode (fluke) eggs are too large and heavy to float reliably in the flotation fluids normally used for nematode eggs, i.e. they have a higher SG, however they do sink rapidly to the bottom of a faecal/water suspension and this is the basis of the faecal sedimentation technique.
- Also, some parasites pass free larvae instead of eggs which cannot be detected by routine faecal flotation.
- The faecal sedimentation method allows detection of large/heavy eggs and certain free larvae.
- This method may also be used for ova that will be distorted or destroyed in the presence of the super saturated salt solutions used in flotation techniques.
The Baermann technique.
• The Baermann technique uses inexpensive equipment, much of
which can be reused, for the detection of larvae in faeces.
• A rubber hose is attached to a funnel and warm water is placed into the funnel into which the faecal sample, wrapped in gauze is placed.
• The warmth of the water activates the larvae in the sample, but they are unable to swim upwards against gravity and as a result will drop through the gauze into the tubing.
• This allows collection of the larvae which can then be centrifuged to concentrate the sample.
• Addition of Lugol’s iodine before examination kills the larvae, making identification easier.
• As well as Angiostrongylus vasorum,the larvae of other lungworms such as Oslerus osleri and Crenosoma vulpis may also be detected using this method.
Coproantigen testing.
• Coproantigen ELISA tests are available for the detection of excretory/secretory
products from intestinal nematodes.
• These tests allow infections to be detected when ova shedding is not occurring and so flotation methods will be ineffective.
• ELISA tests also avoid false positive results due to coprophagia.
• Testing for Giardia faecal antigens is a highly sensitive and specific test, as are recently commercially launched test kits for intestinal roundworms, whipworms and hookworms.
• However, this type of testing indicates the presence of nematodes but gives no indication as to what extent ova shedding is occurring.
• Coproantigen testing is being developed for commercial Echinococcus species testing, and PCR testing of faeces is now commercially available.
Considerations when assessing faecal samples.
• All faecal examinations that rely on the visual detection of parasite eggs, cysts, oocysts or larvae in the faeces have some implicit constraints and may not be indicative of the number of worms present –
• Inaccuracies in counting can occur.
• Microscopic examination of faecal samples cannot detect infestations involving immature
worms or those involving only males.
• Ideal flotation methods may differ for diagnostic stages of different parasites, but due to time constraints and the desire for standardized protocols, a single method is often used for all faecal testing.
• Even though centrifugal flotation has been shown to be superior for parasite recovery from faecal samples, many veterinary practices continue to use a standing, passive flotation.
Other, patient specific considerations include -
• The daily output of eggs by fertile females is influenced by host-physiological factors
such as stress or lactation (increased) or immunity (decreased).
• Chemotherapy can affect egg-production, e.g. corticosteroids (increased) or sub-lethal anthelmintic doses (decreased).
• Some food-stuffs may affect egg production e.g. tannin-rich forages (decreased).
• The concentration of eggs is influenced by the daily volume of faeces being produced by the host, the rate of passage by the ingesta through the intestine, and the distribution of eggs throughout the faecal mass.
• Some eggs from different species are indistinguishable (particularly trichostrongylids and strongylids) which complicates clinical interpretation.
25
- Coprophagic behaviour needs to be identified in dogs prior to testing,
- False positives can occur if dogs are coprophagic prior to testing.
- Strongyle eggs in ruminant and horse faeces will pass through the digestive tract of cats and dogs unchanged, giving the impression that the pet is infected with hookworm.
- Similarly, Toxocara cati eggs may be found in dogs that have eaten cat faeces.
Blood diagnostic methods.
• Dirofilaria immitis (heartworm) infects cats and dogs and is
found in the pulmonary artery of the heart.
• (Although D. immitis is not endemic in the UK, increasing numbers of infected rescue dogs are being imported from endemic countries.)
• Three methods are used to diagnose heartworm infection in dogs –
• Direct Smear – examination of blood on slide.
• Modified Knott’s Test (MKT) – detects and allows identification of microfilariae (larval form of D. immitus) of D. immitis via examination of buffy coat layer.
• Antigen Test – detects adult female heartworm (ovarian) antigens in a serological assay (ELISA methods such as SNAP Heartworm test available).
Direct Smear
examination of blood on slide.
Modified Knott’s Test (MKT)
– detects and allows identification of microfilariae (larval form of D. immitus) of D. immitis via examination of buffy coat layer.
Antigen Test
– detects adult female heartworm (ovarian) antigens in a serological assay (ELISA methods such as SNAP Heartworm test available).
Blood diagnostic method considerations
- The antigen test is the most sensitive test however false negatives can occur –
- In animals with low burden of female heartworms (detects ovarian antigens) or when only male worms are present
- If certain types of wormers have been used that lead to the formation of immune complexes that can block detection of the antigen.
- Animals on heartworm preventive medication become amicrofilaraemic and so the MKT will be insufficient.
- Feline dirofilariasis cannot be reliably diagnosed by microfilaraemia or antigenemia tests, because heartworm numbers are typically too low.
Urine diagnostic methods.
- Urine testing for parasites less relevant for the UK.
- There are several parasites restricted to the urinary system, such as the giant kidney worm (Dioctophyma renale) and bladder worm (Pearsonema plica).
- Ova may be identified by examining urine sediment samples collected through cystocentesis.
Ectoparasite diagnosis.
- Animals displaying dermatoses should always be evaluated for the presence of ectoparasites or signs of their presence.
- Superficial close examination may reveal the presence of certain ectoparasites (lice, ticks, flies) but further methods are required for microscopic parasites or those that live beneath the surface of the skin.
- The techniques described can be used in a range of veterinary species but are most commonly utilised in companion animal species.
Skin Scraping.
- Skin scraping is an easy and effective method that can be used to make a definitive diagnosis of ectoparasitic infestation.
- The edge of a scalpel blade is gently scraped across the surface of the skin in order to collect material which can then be examined under a microscope, usually in a drop of mineral oil on a slide under low power-magnification.
- Addition of 10% potassium hydroxide solution may help to clear debris and allow better visualization.
- Some surface living ectoparasites such as Cheyletiella may be found with a superficial scrape, however those that burrow (Sarcoptes) or live in hair follicles (Demodex) will require a deeper scrape (capilliary ooze).
Interpretation of a skin scrape.
• Finding one mite, egg or deposit of faeces from
sarcoptic mites allows a definitive diagnosis.
• However, as demodex mites are commensals on several species, the significance of one or two mites is not clear.
• False negatives are common with skin scrapes, especially with the deep living forms, and so the absence of a parasite in a sample does not confirm absence on the animal.
Coat Brushings.
• Coat brushings are useful to indicate presence
of fleas and Cheyletiella mites.
• The simplest approach is to place a sheet of white paper below the animal and rub or comb the fur towards the paper.
• Debris removed by this method can indicate fleas through the presence of black, comma- shaped faeces which can be moistened to further confirm presence.
• Debris can also be examined with a microscope to identify presence of mites or eggs.
Tape Strips.
- Tape strips can be useful to indicate the presence of Cheyletiella mites, Trombicula autumnalis (harvest mite) larvae, Otodectes and lice.
- Demodex mites may be seen on these samples if infestation is severe.
- Clear adhesive tape is applied to several locations and then transferred to a microscope slide for examination.
Hair Plucks.
- Hair plucks can indicate the presence of Demodex mites, Cheyletiella eggs, lice and lice eggs.
- Small clumps of hair are plucked and examined under a microscope slide.
Sarcoptes serology.
• A serological (ELISA) test is available for the
diagnosis of sarcoptic mange in dogs.
• Serum IgG antibodies against Sarcoptes antigens are measured.
• It has been reported that the test has 95-98% reliability and a positive result indicates past or present exposure to Sarcoptes scabiei.
• Time to sero-convert to positive is approximately 4 weeks and so false negatives are possible.
• Time to sero-convert back to negative varies between individuals but can be several months thus affecting accurate assessment of treatment success.
Antimicrobial sensitivity testing should:
- Be standardised
* Include the most appropriate antimicrobials • Use the most appropriate methodology
Direct method of getting specimens for the testing of antibiotics
- pathological specimen (e.g. urine, swab of pus etc.)
- Sample is used to inoculate a culture plate
- Single colonies are selected to inoculate a liquid culture
InDirect method of getting specimens for the testing of antibiotics
- Pure culture already isolated
- Sensitivity plate created directly
from pure culture
Disc diffusion (Kirby-Bauer method)
• Solid agar plate (containing suitable nutrients)
• Discs, tablets or strips containing a known concentration of antimicrobial agent
• Pure culture of microbe to be tested
Measures zone of inhibition to find MIC
Minimum inhibitory concentration (MIC)
The lowest concentration of an antimicrobial that will inhibit visible growth of a microorganism after incubation
Dilution methods
- Dilution methods take a volume of antimicrobial to be tested and create a series of dilutions to produce individual tubes or agar plates with a range of strengths of antimicrobial
- A small amount of the microbe of interest is then added and incubated
- The lowest concentration at which there is no visible growth of microbes is identified as the MIC (minimum inhibitory concentration)
E.g agar and broth dilution method
Etest
Etest (previously known as the Epsilometer test) is a way of determining antimicrobial sensitivity by placing a strip impregnated with antimicrobials onto an agar plate. A strain of bacterium or fungus will not grow near a concentration of antibiotic or antifungal if it is sensitive. For some microbial and antimicrobial combinations, the results can be used to determine a minimum inhibitory concentration (MIC) via where the elliptical meets the strip
Molecular methods of antibiotic sensitivity testing
- Many antimicrobial resistance genes have been identified in many different microorganisms
- Molecular methods allow us to identify if a pathogen in our patient sample possesses that gene and would therefore not be susceptible to that antimicrobial
- Offers very rapid, accurate and specific resistance testing
- Currently used alongside disc-diffusion AST for comparison
Clinical breakpoint
The concentration of antibiotic used to define whether an infection by a particular bacterial strain/isolate is likely to be treatable in a patient
efficacy ratio of different antimicrobials can be calculated by
comparing the recorded MIC from the AST with the clinical breakpoint MIC
Breakpoint MIC divided by measured MIC = efficacy
Describe the muscle composition of the Equine Oesophagus
Proximal two thirds skeletal muscle Distal third smooth muscle
Margo Plicatus
A region called the margo plicatus is present which separates the glandular and non-glandular parts of the equine stomach. The non-glandular area is lined with squamous mucosa (not columnar). The glandular portion consists of mucosa
Equine Stomach
- Simple monogastric stomach
- 10-20 Litres capacity
- Anatomy of oesophageal sphincter (the cardia) prevents eructation under normal conditions
- Squamousmucosainfundus–no digestive function
- 2-3 litres of gastric acid produced by glandular mucosa each day
- Veryacidicenvironment(pH4)
Glandular mucosa (equine)
- HCl produced by parietal cells in responseto;
- Parasympathetic action (acetylcholine from vagus nerve)
- Gastrin stimulation from G-cells in the gastric antrum
- Histamine stimulation
- Increase expression of H+/K+-ATPase proton pumps on apical surface of parietal cell
Equine Small Intestine
20-25 metres long – Duodenum(1metre) – Jejenum – Ileum(0.5metre) Function similar to other species • Digestion/absorption of Non-Structural CHO Proteins Fats
“Suspended” from roof of abdomen by the great mesentery
Normally positioned in
left dorsal abdomen
Relatively mobile with long mesentery can lead to;
• Volvulus
• Incarceration/herniation
• Intussusception
Equine Large Intestine – Ascending Colon
Large colon holds 70-80 litres of semi-liquid ingesta
Contains 10% of total body water content
Hind-gut Fermentation
• Starts in caecum
• Microbial digestion of structural CHO to release VFAs for absorption
Equine Taenial Bands
Concentrations of the external longitudinal musculature at various aspects around the circumference of the ascending colon
➢Creates segmentation of the colon = HAUSTRA Formation
➢Haustral ‘flow’ contractions of taeniae to mix
Ingesta
All sections have at least 1 taenial band at the mesenteric attachment
Identifying the number and position of additional bands is key knowledge for evaluating the equine GIT by trans-rectal palpation
How many taenial bands in the caecum
4
How many taenial bands in the right ventral colon
4
How many taenial bands in the left Ventral colon
4
How many taenial bands in the pelvic flexure
1
How many taenial bands in the left dorsal colon
1
How many taenial bands in the diaphragmatic flexure
2
How many taenial bands in the right dorsal colon
3
How many taenial bands in the transverse colon
2
How many taenial bands in the descending colon
2
Equine Caecum
First Section of the Ascending Colon up to 1m long, holding up to 30-35 litres of fluid ingesta
Base
• Fixed in position in right caudodorsal abdomen, occupying right PL Fossa
✓ Retroperitoneal attachment at level of right kidney
✓ Attachment to root of mesentery
✓ Attachments along lumber vertebrae
✓ Attachment to right dorsal colon
Body
• Cylindrical and curved, following right flank
Apex
• Tapered blind-ended apex which sits toward midline, extending to xyphisternum
Ileoceacal junction sits dorsal to the caecocolic orifice
Ingesta spills into the body of the caecum
Peristaltic contractions begin at caecal apex to move ingesta up to the caecal base and toward the caecocolic orifice
Enters into the Right Ventral Colon
Equine Ascending Colon – Sections and Flexures
Main body of the ascending colon is “divided” into 4 sections and 3 flexures, based on their topographical location within the abdomen Right Ventral Colon Sternal Flexure Left Ventral Colon Pelvic Flexure Left Dorsal Colon Diaphragmatic Flexure Right Dorsal Colon
Equine Ascending Colon
Ventral and Dorsal colons closely bound by mesocolon
Left Ventral colon narrows as it reaches pelvic flexure
Pelvic flexure is 180-degree bend in colon
Pelvic flexure and left dorsal colon only have 1 taenial band, and no haustra formation
Entire left colon sits ‘free’ within the abdomen, with no body wall attachments
Equine Descending Colon
Heavily segmented, narrow aspect of colon, leading to rectum
Final Reabsorption of water
Formation of faecal balls
Sits within left caudodorsal aspect of abdomen
Arteries in the equine GIT
Caudal Mesenteric Artery
Cranial Mesenteric Artery
Splenic Artery
Coeliac Artery
Nephrosplenic Ligament & Nephrosplenic Space
The nephrosplenic ligament connects the left kidney to the spleen in the horse.
Clinical significance as left colon can become entrapped in this space
Veterinary epidemiology
- thestudyofthedistributionanddeterminantsof
animal health, welfare and production
• The goals are to determine the frequency and distribution anb risk factors for the disease
• Epidemiology – mainly concerned with populations rather than individuals
• Key question often asked by epidemiologists – what is the denominator – the population from which cases came from
• Estimates the frequency of events by:
a. countingthenumberofhealth-relatedeventswhichoccur
within a specified time in different populations b. takingthedenominatorintoaccount
• Help compare occurrences between different populations.
Descriptive epidemiology:
- examine the distribution of disease in a population - observing the basic features of its distribution
Analytic epidemiology:
- investigate a hypothesis about the cause of disease by studying how exposures relate to disease
The epidemiologic triad/triangle
– consist of an external agent, a susceptible host, and an environment that brings the host and agent together.
• Disease is the result of forces within a dynamic system consisting of:
- Agentofinfection
- Host
- Environment
Host
- behaviours
- genetic predisposition
- immunologic factors
Agents
- biological - physical
- Chemical
• Influence the chance for disease or severity
Agents
- environment
- external conditions - physical/biological
• Contribute to the disease process
Heterodonty
heterodont (of an animal) possessing teeth of more than one kind, such as incisors and molars
four types of teeth
incisors
canines
pre molars
molars
decidous dental formulae of the cat
3130/3120
= 26 teeth
permanent dental formulae of the cat
3131/3121
= 30 teeth
decidous dental formulae of the dog
3130/3130
= 28 teeth
permantent dental formulae of the dog
3142/ 3143
= 42 teeth
Brachydont
-(‘short teeth’)-Carnivores, omnivores, incisors ruminants
Do not grow continuously.
Carnivores have specialised teeth for grasping and tearing: canines and carnassials.
Hypsodont
(‘long teeth’)- herbivores
Most teeth of herbivores except incisors of ruminants.
Erupt throughout life.
Have complex grinding surfaces: cement covers enamel of hypsodont teeth
horse dental formulae
3-1-4-3/ 3-1-4-3
the insisor is only sometimes present and mostly in males
Jaw size and shape of horse
Head of mandible is larger in species where lateral grinding of food matter is the predominant movement, and disk of TMJ thicker.
Third joint at mandibular symphysis allows for crushing and cutting by the jaw of carnivores eg dog.
judging Ageing
of horses
By stage of eruption of permanent dentition- up to 5 years old
By shape owing to wear and eruption
Ageing by wear on incisors
angle of incisors
descriprion of horse teeth at 6 days
1st deciduous incisor erupts
descriprion of horse teeth at 6 weeks
2nd deciduous incisor erupts
descriprion of horse teeth at 6 month
3rd deciduous incisor erupts
descriprion of horse teeth at 1 year
3rd deciduous incisor in wear
descriprion of horse teeth at 2 1/2 year
1st permanent incisor erupts
descriprion of horse teeth at 3 1/2 year
2nd permanent incisor erupts
descriprion of horse teeth at 4 1/2 year
3rd permanent incisor erupts
descriprion of horse teeth at 5 years
First and second incisors level, all cups present
descriprion of horse teeth at 6 years
Cups begin to disappear
descriprion of horse teeth at 8 years
Cups gone, stars appear
descriprion of horse teeth at 10 years
Incisors become round
equine paranasal sinuses
frontal sinus
caudal maxillary sinus
rostral maxillary sinus
frontomaxilary sinus
Trephination
creating a hole in the skull- in this instance allows access to the sinuses to flush out debris and infection.
Nasolacrimal duct
he nasolacrimal duct (also called tear duct, latin: ductus nasolacrimalis) is a channel that is directly continuous with the lacrimal sac and opens into the nasal cavity, forming the final part of the tear drainage system of the lacrimal apparatus.
the horse has how many thoratic vertebrae
18
the equine heart sits between ….
the 3rd and 6th rib
the horse has how many lobes in the lung
none, it is unilobular
Tracheal wash
samples from trachea
Bronchoalveolar lavage
samples from lower airways
what do th extrenal inetercostal muscles do in respiration
elevating the ribs and expanding the chest cavity to trigger in inhilation
what do th internal inetercostal muscles do in respiration
assist with exhalation and moving the ribs and chest cavity back to their original position.
Visceral Piston Effect (equine)
Gastrointestinal tract swings cranially as forelimbs hit the ground, pushing against the diaphragm and compressing the thorax, forcing air out
Gastrointestinal tract swings caudally as hindlimbs are loaded, drawing the diaphragm caudally drawing air into the lungs
Links stride frequency to respiration
what does PAM stant for in regards to auscaultation the heat of a horse and whaere are these points located
Pulmonary valve- 3rd Intercostal space
Aortic valve- 4th Intercostal space
Mitral valve – 5th Intercostal space
(on the left side)
how and where do you auscultate the tricuspid valve of the horse
Tricuspid valve- 5th intercostal space on right hand side
describe the structures important to the pallate in the horse
Pharynx: oropharynx, nasopharynx and laryngopharynx
Nasopharynx something really unusual: entry to the auditory tubes (=guttural pouches)
Hard palate (palatine bone) and soft palate which separates oropharynx from nasopharynx
Soft palate free border stuck under the epiglottis: nasal breather and not able to vomit*
Palate muscles: levator veli palatini and tensor veli palatini, palatinus and palatopharyngeus
Lymphoid tissue in the palate
muscles controlling the soft pallet
tensor veli palatini
levator veli palatini
palatinus
palatopharyngeus
function and innervation of the tensor veli palatini
tenses rostral aspect of the soft pallet
innervaded by the mandibular branch of thr trigeminal nerve
function and inervaation of the levator veli palatini
elevates the pallet durning swallowing and closes the nasopharnyx
pharyngeal branch of the vagus
function and innervation of the palatinus
shortens and deperesses the palete
pharyngeal branch of vagus
function and inervation of the palatopharungeus
shortens and depresses the pallet
paharyngeal branch of the vagus
function and innervation of the Stylopharyngeal muscles (nasopharyngeal wall)
Elevates pharynx and larynx Glossopharyngeal nerve (CN IX)
equine Soft palate
regulates entry of air in upper airway If dysfunction of the SP goes above the epiglottis DDSP (“gurglers”?) Close relation with tongue and associated musculature (tongue tie) Lymphoid tissue (palate, pharyngeal wall and tongue tonsils)
name the bones of the hyoid appaeratus
stylohyiod epihyoid thyrohyoid cerahyoid basihyoid
name the hyoid muscles
geniohyodeus, sternohyoideus, omohyodeus, thyrohyoideus
Laryngeal cartilages:
Arytenoid
Epiglottis
Thyroid and cricoid (not visible on endoscopy but palpable during CE)
Rima glottis (or rima glottidis)
Intrinsic laryngeal muscles:
CAD CAL Crycothyroideus Vocalis Ventricularis Arytenoideus transversus
Extrinsic laryngeal muscles:
Hyoepiglotticus (controversy about epiglottic position?)
Thyroihyoideus pulls larynx forward
Sternothyrohyoideus pulls larynx caudally and ventrally
what nerves innervate the laryngeal muscles
Cranial and caudal laryngeal nerves (branches of the vagus, X)
what is th efunction and innervation of the crycothyroideaus
tenses vocal folds indirectly by pullung the cricoid caudally
crainail laryngeal branch of vagus nerve
functions and inervation of the CAD
opens rima glottis (abducts vocal process of ary tenoids and folds)
caudal recurrent laryngeal branch of vagus nerve
functions and innervation of the CAL
narrows the rima glottis
Caudal recurrent laryngeal nerve (branch of vagus
rima glottis
narrowest point of the cavity of the larynx
function and innervation of the Vocalis
rensing the vocal cords
Caudal recurrent laryngeal nerve (branch of vagus)
ventricularis
tensing the vocal folds
Caudal recurrent laryngeal nerve (branch of vagus)
arytenoideus transversus
adduction of rima glottis but opens vocal cords
Caudal recurrent laryngeal nerve (branch of vagus)
Dynamic endoscopy of the larynx can show
abnormalities during exercise (DDPS, RLN, EE, etc…)
Larynx: functions
Glottis closes forcing pressure from abdominal press leads to cough
Glottis closes when effort (defecation, micturition, parturition) maintaining intrathoracic pressure
Full opening during breathing
Phonation (vocal folds and ventricles)
(in cats purring = larynx muscles)
Protection from inhalation of food
Together with tongue and palate deglutition
Larynx: sections
Vestible
Glottic cleft (middle part)
Infraglottic
Guttural pouches
2 large, air-filled sacs ONLY IN THE HORSE connecting with the auditory tube and pharynx
Lined by mucous membrane
Close to vital structures: pharynx, larynx, arteries, nerves and hyoid apparatus
Strangles (bacterial infection), GP mycosis (fungal infection)
Thought to be to cool the brain during exercise (envelop the cranial arteries)
Cranial nerves affected in GP pathology
IX glossopharyngeal nerve, X vagus nerve, XI acessory nerve, XII hypoglossal nerve, Pharyngeal branch of glossopharyngeal nerve, pharyngeal branch of vagus nerve, cranial laryngeal nerve, cranial cervical ganglion
Guttural pouch mycosis and strangles
Effect on essential structures! Remember:
Internal carotid artery
Glossopharyngeal, vagus, accessory, hypoglossal nerves
Sympathetic trunk
External carotid artery
Internal carotid artery
clinically relevent Vessels and nerves
in the equine head
Jugular vein – iv injections
Transverse facial vein – blood collection
Common carotid artery – avoid during iv injection in neck!!!
External carotid artery – in guttural pouches
Internal carotid artery – in guttural pouches
Linguofacial artery – pulse
important veins in the equine head
external jugular vein dilation of transveres facia vein lingofacialus carotis communis lingofacial vein ext. jugular vein recurrent laryngeal nerve commin carotid artery
clinical relevence of the facial sinus in the horse
located just below the facial crest at the level of the middle of the eye
used for transvere facial blood sample collection
direct blood pressure monotoring in an the anethetized horse by
placing a catheter in the facial artery, transverse facila artery or dorsal metatarsal artery
equine Trachea
Rigidity from the rings but also susceptible to collapse due to air pressures
Smooth muscle contraction from the trachealis makes the trachea easier to collapse than in other species
Some breeds more prone to tracheal collapse (TC) (Shetlands for example)
clinical procedures of the trachea
Tracheal examination during CE
Endoscopic appearance, tracheal wash
Endotracheal tube for GA
Emergency tracheotomy for compromised airway
differences in the male horse compared to other species
Entire male = stallion. Castrated male = gelding
No splanchnic skeleton – no os penis
Additional accessory glands: 2 vesicular glands and 2 bulbo-urethral glands – produce seminal fluid (rest are the same)
name components of the equine penis
vesicular glands ampulla deferent duct epidydimus penis glans penis testis blader retractor penis muscle bulborethral glands prostate prepuce fossa glandis urethral process
what types of tissues would you see in a cross section of the equine penis
tunica slbugenea
corpus cavernosum
corpus spongeum
name componetnts of the testes
deferent mesoduct deferent duct deferent duct artery mesochium tail of epididimus ligament of tail of epeididimus proper ligament of testes liberal border of the testes testicular artery paniform plexus body of epididimus head of epeididimus
describe open vs closed castration in horses
During open castration, one incision is made over each testicle, but rather than being closed with sutures, they are left open so that they can drain and heal freely.
Closed Castration
Closed castrations must be performed under sterile conditions at your equine veterinarian’s surgery and under a general anesthetic. While the procedure is the same, in a closed castration the wounds are sealed using sutures. This significantly reduces the likelihood of hemorrhaging, but the wounds are unable to drain as well as those in open castrations and many horses will develop reasonable swelling at the castration site in the days or even weeks after the operation.
deferent duct
The ductus deferens is a muscular tube that is located within the spermatic cord and is a major component of the male reproductive system. It is a continuation of the epididymis and is involved in transporting spermatozoa from the epididymis to the ejaculatory ducts.
epidydimus
The epididymis is a long, coiled tube that stores sperm and transports it from the testes. It appears as a curved structure on the posterior (back) margin of each testis. It is comprised of three sections. These are the head, body,and tail.
name componetns of the Spermatic cord:
Deferent duct Testicular artery Testicular vein (p plexus) Lymphatic vessels Nerves Cremaster muscle - together with pampiniform plexus = cooling
descibe the technique used to castrate horses
During castration we separate the deferent duct and then the rest (cranial vascular part) to emasculate them separately (most common technique)
descirbe the vascular supply to the testes
Testicular artery (from abdominal aorta) well packed within the cord Testicular veins (forming the plexus pampiniformis) coil around the artery and reduced to a single vein which drains in the caudal vena cava Arteriovenous anastomoses within the cord
describe the lympahtics within the testes
Lymphatic vessels drain into lumbar lymph nodes and iliac lymph nodes (testicular hormones)
describe the innervation of the testes
Parasympathetic fibers (vagal nerve and pelvic plexus) Sympathetic fibers from cd mesenteric plexus and pelvic plexus
describe some complications that can occur involving the equine testes
Testicular haernia – wide inguinal canal. On CE testicular torsion and haernia difficult to tell apart unless ultrasound
Testicular torsion
Abscess/haematoma
describe equine sperm deposition
Erection>emission>ejaculation
Erection: relaxation of penile musculature and penis extrudes + increase of blood flow
Emission: semen passes from the epididymis and mixed with seminal plasma > ejaculation: passes through the penis and outside the male and into the mare repro tract (through intromission)
intra uterine (natural breeding) or the uterine body (artificial insemination) unless done transendoscopically (very unusual) when it is left in the papila
when does the stallion reach amximal reproductive capacity
5 years
when does the stallion reach puberty
2 years (sometimes earlier)
spermatogenisis in the stallion takes
55-57 days
libado and mating behaviour in the stallion is at its peak in….
april to september (long days)
name the stages of the equine reproductive cycle
pro-oestrus (inscrese in FSH) oestrus (increase in oestrogen and LH) metoestrus (increase in progesterone) (possibly birth) anoestrus (no hormones)
leanght of equine cycle
21 days
describe equine pro-oestrus
FSH is growing and growing promoting Graafian follicle growth. Oestrogens are starting to go up (produced by the follicle) which lead to the flirty behaviour (review the AMHP notes on breeding!). Lasts around 9 days
describe equine oestrus
kicks in with the surge of LH which leads to the egg being released. After the release of the egg into the oviduct, the tissue left behind starts scaring turning into CL which produces progresterone. It lasts 2-5 days
describe equine metoestrus
Metoestrus is a phase dominated by progesterone. Up to 56 days. This is when pseudocyesis occurs (false pregnancy) towards the end when P4 is decreasing and prolactin increasing. After CL the scar turns into a Calbicans
describe equine anoestrus
no activity. This could last months
decribe the componests of the equine female reproductive system
uterus crvix vagina vestebule ureathra vulva clitorus uterine horns ovaries broad ligamet
names the componets of the evuine ovary
ovarian artery ovarian veins medulla (vascular zone) cotex (parenchymatous zone) corpus luteam ovulation fossa graphian follicles
descibe the equine ovaries
Cranioventral to the iliac wings
Mesovarium allows mobility – laparoscopy through flank for Gran cell tumour
Up to 10 cm long with an ov fossa
CL and growing follicles more challenging to asses without U/S
descibe the three parts of the oviduct in the horse
: the infundibulum (funnel-shaped portion nearest the ovary), ampulla (expanded middle portion), and isthmus (narrowed portion connecting the ampulla (fertilisation point) to the uterine horn).
equine uterotubal junction (UTJ),
Sperm gain access to the oviduct through the uterotubal junction (UTJ), which is located in the center of the oviductal papilla that projects into the uterine lumen near the blunt end of the uterine horn. Deep, edematous longitudinal folds are present in the UTJ during estrus, and numerous sperm can be found “bound” to epithelial cells or “trapped” in these folds within 4 hours of breeding. The UTJ may play a role in the selection of morphologically normal sperm and may also act as a storage site for sperm awaiting transport into the oviduct.
In the mare, the mesometrium attaches to……
the dorsal surface of the uterine horns, whereas in the cow the attachment is on the ventrolateral surface. Therefore in mares the free (unattached) surface of the uterus is ventral to the broad ligament, whereas in cattle the free surface is dorsal to the broad ligament.
what can be felt and done with a rectal exam on the mare
Uterine horns – easy to palpate Fluid/oedema on U/S ”Pinch” for terminating twin pregnancies Body short Cervix tone and oedema-lacerations Presence of all the structures Size ovaries Uterine tone and size Cervical tone Recognition of big uterine cysts Recognition of pain in ovary (behavioural consults) PD after 13-14 days with ultrasound – much later with RE and depends of experience of vet
caslick surgery
Caslicks is an operation to partially suture together the lips of the vulva. Caslicks are used to prevent fecal contamination problems in mares that have abnormal vulva conformation
Breeding soundness examination (‘MOT’)
Old mares (>12 y.o.) Thoroughbred mares: commonly done at the beginning of the breeding season to all mares Essential Programmes with artificial insemination and/or embryo transfer
Pregnancy diagnosis
in mares
Day 14 maternal recognition of pregnancy starts (otherwise PGF2a)
As early as 10 days (most VSs do 13-14 days) pregnancy vesicle on ultrasound PD
Unusual rounded embryo that moves about more than other species and it is covered in a “rounded” protective layer of sugars that disappears around day 23* (blastocyst capsule) when fixation occurs
A critical point is day 45 when CL can start to break down but it is replaced by accessory CLs (progesterone). After 5th month, placenta takes over the production of progesterone
Day 25 starts the formation of the chorionic girdle – cells on day 38 migrate inside the uterine wall to form the endometrial cups
Day 28 development of sinus terminalis (future umbilical cord)
Day 35 organogenesis completed (after day 35 we can call it foetus)
Day 45 early placenta leads to microplacentomes (microcotyledones with microcaruncles)
Endometrial cups = Circular horseshoe pale irregular outgrowths that reach peak size day 70 then regress (130 days disappear) produce eCG, thought to stimulate secondary CLs for pregnancy maintenance
Day 45 is critical: if pregnancy loss after this it takes up to 3 months to get back on heat because of the cups!
PD checks: 13-14 days (twins!! Mindful not to mistake embryo with cyst!!), then 21 (if AI or valuable as it will be inseminated for the next cycle), then 45 days.
describe the palcenta of the horse
Placenta is diffuse, microcotyledonary and epitheliochorial
descibe the mamory glands of the mare
Two mammary glands, much smaller than cows Small in non pregnant young mares Each gland has two separate duct systems Inside very similar to cattle External pudendal artery Pudendal vein + lateral thoracic vein Lateral thoracic vein very marked in pregnant mares
Useful kits to have for mares
: milk electrolytes test for predicting parturition (sodium drops below K, increase of Ca+2 are signs of imminent 24 to foaling)
IgG milk content for testing IgG to ensure foal has good passive immunity
List the main differences in the accessory glands between stallions, dogs and cats
dogs have: prostate gland
cats have: bulbourethral gland
and prostate gland
horses have: vesicular gland, ampulla of defertn duct and, prostate gland anf bulboourethral gland
Ovulation fossa
n the concave surface of the ovary is the ovulation fossa where the oocyte is expelled from the ovary
Endometrial cups
Circular horseshoe pale irregular outgrowths that reach peak size day 70 then regress (130 days disappear) produce eCG, thought to stimulate secondary CLs for pregnancy maintenance
vessels and nerves of the horse of clinical importance
Jugular vein – iv injections
Transverse facial vein – blood collection
Common carotid artery – avoid during iv injection in neck!!!
External carotid artery – in guttural pouches
Internal carotid artery – in guttural pouches
Linguofacial artery – pulse
Prevelance
Prevalence, sometimes referred to as prevalence rate, is the proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time
what bones make up the equine distal forelimb
3rd metacarpal bone (cannon bone) 4th and 2nd metacarpal bone (splint bones) proximal sessamoid bones proximal phalanx (p1, cannon bone) middle phalanx bone (p2, pastern) distal phalanx (p3, coffin bone)
extensor tendons of the equine distal limb
(not prone to injury)
Common Digital Extensor Tendon
Courses distally over dorsal aspect of cannon, fetlock and pastern
Inserts on extensor process of P3
Lateral Digital Extensor Tendon
Lies dorsolateral to cannon
Inserts on dorsal aspect of P1
extensor tendons of the equine distal limb
(not prone to injury)
Common Digital Extensor Tendon
Courses distally over dorsal aspect of cannon, fetlock and pastern
Inserts on extensor process of P3
Lateral Digital Extensor Tendon
Lies dorsolateral to cannon
Inserts on dorsal aspect of P1
flexor tendons of the distal equine limb
Superficial Digital Flexor Tendon (SDFT)
Inferior Check Ligament
Deep Digital Flexor Tendon (DDFT)
Suspensory Ligament
sessamoidean support ligaments of the fetlock joint
Sessamoidean Ligaments Straight Oblique Cruciate Short
annular support ligaments of the fetlock joint
Palmar Annular Ligament
Proximal Digital Annular Ligament
Distal Digital Annular Ligament
pints for nerve block on the equine distal forelimb
low 4 point
Abaxial Sessamoid
palmar digital
Low 6-Point
pints for nerve block on the equine distal forelimb
low 4 point
Abaxial Sessamoid
palmar digital
low 4 point nerve block
deep nerves course between the splint bones and the cannon bone on the axial surface of the splint bones-block just distal to the end of the splint bone
This block numbs the fetlock and distal cannon bone (palmar or plantar aspect).
Palmar Digital
(Heel Block) – The block targets the back of the foot. It is injected over the palmar digital nerve just under the skin. It blocks the heel bulbs, frog, navicular bone, navicular bursa, the coffin joint, and the phalanx.
low 6 point nerve block
blocks lateral and medial plantar nerves and lateral and medial metatarsal nerves the same as 4 point block in forlimb
indlimb hower has dorsal metatarsal nerve and hence doral surface is alo blocked
equine distal limb- digital flexor sheath
a synovoial flud space that surrounds the flexor tendons as they course around the bottom third of the cannon bone and the fetlock joint and disperse throughout the pastern region
case study
Observational, descriptive
Careful, detailed description of a single case or series of cases (typically by observant clinician(s))
Analysis: narrative description, simple descriptive statistics (case series)
• Select people based on outcome
• Select people with and without lung cancer and ask about habits
• Good for rare diseases
• Quick and inexpensive
• Lack temporality
• Recal bias- inaccurate data
• Can’t estimate prevalence or incidence
May be the first clues of new diseases, outbreaks, impact of a condition, unsuspected adverse effects, possible
exposures
no comparason group
crossectional study
- A snap shot in time
- Quick and cheap
- Data collected at one period of time
- Large Heath surveys
- Census data
- Do they smoke? Yes no
- Lacks temporality- what came first? Smoking or lung cancer
- Can estimate prevelance
Observational, analytical
Careful, detailed description of study population (time and place)
Exposures and outcome/disease status are assessed the same time
multiple exposures or outcomes
high suceptability to bias
cohort study
- Select people based on exposure
- Eg selecting people based on whether they smoke
- Has temporality
- Follows people over time
- Take a long time
- Expensive
- Loss to follow up issues
- Incidence can be measured
- Prospective or retrospective
Observational, analytical
Careful, detailed description of study population and exposures (risks)
Starts at the time of the exposure – follow-up until outcome occurs
randomised control trial
• Similar to cohorts
• People are randomly assigned to exposures
• Might be unethical to expose or not expose the group to certain factors
• Balance out confounders
• Long
• Expensive
Experimental, analytical
Prospective cohort design
Starts at the time of exposure (intervention) – follow-up until outcome occurs
Key features:
Control arm (no exposure) Random allocation of exposure to intervention groups: similar baseline characteristics; similar distribution of confounders Blinding of participants (e.g. owners) and clinicians (where possible)
randomised control trial
- Similar to cohorts
- People are randomly assigned to exposures
- Might be unethical to expose or not expose the group to certain factors
- Balance out confounders
- Long
- Expensive
Case control designs
Observational, analytical
Compares cases (diseased animals) and controls (non-diseased animals) with respect to their level of exposure to a suspected risk factor
Starts with the disease (or outcome of interest) and looks back at prior history of exposures
“all the effects are already produced before the investigation begins”
investigates multiple exposures
well suited to rare disease with long latency
quick and inexpensive
suseptable to bias: selectional bias, information bias
lacks temporality
Information bias
Exposures and outcomes are not measured well, or not in a similar way in all study participants (animals)
Information bias: assessment of exposure varies depending on risk of experiencing the outcome / disease status
Information bias
Exposures and outcomes are not measured well, or not in a similar way in all study participants (animals)
Information bias: assessment of exposure varies depending on risk of experiencing the outcome / disease status
describe the components of the equine forelimb
Scapula: scapular cartilage
Humerus: greater tubercle = point of the shoulder
Olecranon (ulna) = palpable point on elbow
Radio and ulna fused
Accessory carpal bone = palpable point on carpus/knee
Chestnut
Ergot
Equine joints of the forelimb
Proximal to distal: Shoulder Joint Elbow Joint Carpal joint – (Knee!) Metacarpophalangeal joint – (Fetlock joint) Proximal interphalangeal (PIP) joint – pastern Distal interphalangeal (DIP) joint – coffin joint
function and innervation of the trapezius
Protracts & abducts forelimb. The cervical part acting alone swings the scapula forward, which advances the limb, whereas the thoracic part acting alone swings it in the opposite direction. Accessory nerve.
function and inervation of the brachiocephalicus
Limb on floor: flexes the neck & bends it laterally. Not on floor: protracts foreleg. Accessory cervical and axillary nerves.
function and inervation of the brachiocephalicus
Limb on floor: flexes the neck & bends it laterally. Not on floor: protracts foreleg. Accessory cervical and axillary nerves.
function and innervation of the omotransversius
Draws the FL forward. Accessory nerve.
function and inervation of the lattisimus dorsi
Retracts limb (antagonist of brachiocephalicus) & flexes shoulder. Thoracodorsal nerve.
function and innervation of the pectoralis transversus
Adduction and protraction/retraction of limb. Pectoral branches brachial plexus
function of the rhomboideus
Extends and raises the shoulder; pulls the scapula cranially and dorsally. Raises the head
function of the serratus ventralis
Supports the trunk and rotates scapula. The cervical part rotates the bone so that the ventral angle is carried caudally, thus retracting the limb; contraction of the thoracic part advances this angle and thus the limb.
funtion and innervation of the pectoralis profundus
Adduction and protraction/retraction of limb. Pectoral nerves.
function and innervation of the subclavius
Adduction and protraction/retraction of limb. Pectoral nerves.
how to tap the shoulder joint
The cavity is relatively capacious. It may be tapped by inserting a needle at the cranial margin of the palpable infraspinatus tendon about 2 cm proximal to the caudal part of the greater tubercle. The needle is directed ventromedially and must be introduced about 4 or 5 cm before its tip penetrates the capsule.
The procedure requires some care because a cranial deflection may cause the needle to enter a quite separate synovial sac, the bursa that protects the biceps tendon within the intertubercular groove. This intertubercular bursa corresponds to the diverticulum of the joint capsule found in the dog and sheep. (Dyce)
describe the bones and muscles of the equine shoulder
Bones
Scapular spine and cartilage
Point of the shoulder (cranial part of the greater tubercle humerus)
Muscles:
Lateral: supraspinatus, infraspinatus, deltoideus (and teres minor)
Medial:
subscapularis, teres major, coracobrachialis (and capsularis)
describe the bones and muscles of the equine shoulder
Bones
Fused radius and ulna
Muscles:
Flexors: biceps brachii and brachialis
Extensors: triceps, tensor fascia antebrachia, anconeus
descrine the bones and muscles of the equine carpal region
Bones
Distal radius and ulna, carpal bones
Muscles:
Flexors: Flexor carpi radialis, flexor carpi ulnaris, superficial digital flexor, deep digital flexor
Extensors: Extensor carpi radialis, commond digital extensor, lateral digital extensor, ulnaris lateralis, extensor carpi oblique
describe the function of the bicepts brachii
flexes elbow
describe the function of the brachialis
flexes elbow
describe the function of the triceps
extends elbow
describe the function of the tensor facia antebrachia
extends elbow
describe the function of the anconeus
extends elbow
describe the function of the common digital extensor
Extension of carpus, phalangeal joints, and flexion of elbow. Toe extension
describe the function of the deep digital flexor
Extension of elbow, flexion of carpus, and phalanges. Toe flexion
describe the function of the lateral digital extensor
Extension of carpus and phalangeal joints
describe the funtion of the superficial digital flexor
Extension of elbow and flexion of carpus and phalangeal joints
Can you name the muscles that you might jab during intramuscular injection in pecs, neck and rump?
Neck: Trapezius/serratus cervicalis
Chest: (desc) Pectoral
Rump: (sup+deep) Gluteal
Rear end: semitendinosus/semimebranosus
describe the componetns of the equine hindlimb
Ilium – tuber coxae (point of the hip) and tuber sacrale
Ischium – ischiatic tuberosity (=tuber ischii or point of the buttock)
Stifle joint – no fabellae
Gaskin: between stifle and hock
Tibia and fibula fused
Point of the hock - calcaneus
describe the joints of the equine hindlimb
Proximal to distal: Sacroiliac Coxofemoral joint - (hip joint) Stifle joint (patellar ligaments) Tarsus – (Hock joint) Metatarsophalangeal joint (Fetlock) Proximal interphalangeal (PIP) – or pastern Distal interphalangeal (DIP) – or coffin joint
describe the sacroilliac joint
Synovial joint with fibrous union – shock absorber and point of attachment HL
Not very mobile – 1 degree flexion and extension
Sacroischiatic ligament (instead of sacrotuberous ligament) – sheath
Sciatic nerve, cranial gluteal nerve and cranial gluteal artery and vein close to SIJ
describe the equine pelvis
Four bones fused (glued) together:
Ilium
Ischium
Pubis
Acetabular bone in some species (in the dog they simply converge in the acetabulum)
Pelvis articulates with sacrum (sacroiliac joint) and femur (hip joint)
describe the componetnts of the equine hip joint
Extra ligament – accessory ligament Movements of extension and flexion Muscles: Gluteal group Caudal group Medial group Cranial group
describe the components of the equine stifle joint
Patella Lat troch ridge Med troch ridge Med meniscus Med pat lig Int pat lig Lat pat lig Med coll lig Lat coll lig Lat meniscus Tibial tub Med femoropatellar lig Diarthrosis Femoropatellar compartment Femorotibial medial compartment Femorotibial lateral compartment
describe upward fixation of the patella
Medial patellar ligament (4) locks the patella (1) and femoropatellar ligament (2) dorsally to the prominent medial ridge of the femoral trochlea (3) preventing stifle flexion and leading to lameness and abnormal flexion-extension of the hindlimb
name the tarsal bones in the horse
Proximally bones: Tibial tarsal or talus (sits medially) (5) Fibular tarsal or calcaneus bone (os calcus) (sits laterally and caudally) – tuber calcis (point of the hock) (9-10-11) Intermediate row: Central tarsal bone (CT) (12) Fused I and II tarsal bones (13+14) Distal row: III tarsal bone (15) IV tarsal bone (16)
capped hock
A capped hock is basically bursitis of the hock. Bursitis is when the bursae (sac of fluid) of a joint becomes inflamed. In the case of a hock, this is due to an injury or trauma. Likely horse scenarios that create this trauma include a bang to the hock (fence, trailer, other horse) or even a kick inside a stall.
describe the equine hock
Joints:
Tarsocrural joint+proximal intertarsal
Intertarsal
Tarsometatarsal
Ligaments:
Same ligaments as dog – plantar ligament important
Check ligament
Extensor retinaculae
Bursae: Calcanean bursa Tarsal sheath Craniolateral: Tibial cranialis Peroneus tertius Long digital extensor Lateral digital extensor Caudal: Gastrognemius Superficial digital flexor Deep digital flexor
describe the function of the tibial cranialis
flexes tarsus
describe the function of the peroneus tertius
simply a tendon. Flexes tarsus. Important in passive stay apparatus
describe the function of the long digital extensor and lateral digital extensor
Flexes tarsus and extends digit
describe the function of the gastrognemius
in theory extends tarsus and flexes stifle but this does not happen in horses due to reciprocal apparatus
describe the function of the super digital flexor
Flexes stifle, extends hock, flexes digit
describe the function of the deep digital flexor
extends tarsus, flexes digits
equine Stay apparatus
Strategy for sleeping while standing. Joints lock and muscles relax
Made by: appendicular skeleton, several muscles, biceps tendon, suspensory ligament, check ligaments, patellar ligaments (stifle joint) peroneus tertius, DDFT and SDFT
equine suspensory ligaments
Suspensory ligament Prevents fetlock collapse Sesamoid ligaments: (fetlock region) Intersesamoidean lig Collateral sesamoidean ligaments Distal sesamoidean ligament Straight sesamoidean ligament
describe the locking mechanisms of the equine forelimb
Shoulder is locked by the biceps tendon
Carpus is locked by the carpi radialis muscle (extensor)- lacertus fibrosus
Fetlock is locked by the suspensory apparatus, check ligaments, superficial and deep flexor tendons (SDFT and DDFT)
Pastern is locked by the axial and abaxial (pastern joint), palmar lig and straight sesamoidean ligament
describe the locking mechanisms of the equine hindlimb
Below the hock, same as forelimb
Peroneus tertius muscle locks stifle and hock, acting as a flexion/extension antagonist to the stifle and hock when the stifle is straightened.
In stifle extension, patella moves proximal and rotates medially. This movement allows the parapatellar cartilage and medial patellar ligament to hook over the medial patellar ridge, locking the stifle joint
List the ways the equine distal limb has evolved to maximise speed and efficiency of locomotion
unguligrade stance of the horse (single toed), the patellar locking mechanism, and the stay (reciprocal) apparatus,
in a live limb the digital flexor tendons and ligaments on the flexor side of the limb prevent failure. Tendons have elastic properties and act like rubber bands or springs, providing resistance against which the limb presses when it comes under load, thus resisting further hyperextension and preventing collapse (Figure 26-1). The tendons are stretched at the same time, thus storing elastic strain energy, which can be returned in elastic recoil. During each step energy is stored, and it is returned when the limb leaves the ground. Energy is carried forward from one step to the next, thus reducing work the muscles have to do and saving metabolic energy. Indeed, the muscles associated with the main contributors of this system—the suspensory ligament (SL), deep digital flexor tendon (DDFT), and superficial digital flexor tendon (SDFT)—either are not present at all (the SL and the accessory ligament of the DDFT [ALDDFT]) or are very short in relation to the tendons
To enable a pogo-stick design, the bones in the equine limb are reduced compared with other animals: the radius and ulna are fused, and the horse bears weight only on the third metacarpal bone (McIII) or third metatarsal bone and the digit. Fewer bones allow lengthening of the limb and tendons and reduction of the mass of the distal aspect of the limb. This increases the energy storage capabilities of the digital flexor tendons and also results in a lighter limb that can be swung more rapidly and with less energetic cost, which is of benefit in locomotion. Fewer bones is thus an adaptation for maximum strength with minimum weight,
The foot has a series of “built-in” protective mechanisms that absorb part of the concussive forces and damp vibrations during impact (Figure 26-2):
1 The shape of the solar surface with the frog in the middle and the frog sulci (grooves) on either side allows the heel to move sideways and distally on ground contact while the toe retracts.
2 The suspension of the distal phalanx within the horn capsule allows forces to be transferred from the distal phalanx across the laminar junction to the hoof and to the ground via the distal border of the hoof wall.
3 The digital cushion located under the frog and sole between the cartilages of the foot is a wedge of elastic subcutaneous tissue, consisting of collagen, elastic fibers, islands of cartilage, fat, and modified skin glands; this cushion aids in shock absorption by deforming and permitting the frog to move. The equine digital cushion, however, is small in comparison to that in other species—for example, the elephant limb, which relies heavily on its large digital cushion for shock absorption.
4 The hoof has the ability to slide along the ground surface.
5 The distal interphalangeal (DIP) joint can move by rotation and translation.
name the componetns of the external anatomy o f the equine hoof
. Bulb of heel
- Angle of sole
- Bar
- Sole
- Apex of frog
- Central sulcus of frog
- Collateral groove
- White line
- Hoof wall
the jointa in the equin efoot are
synovial
name the layers of the equine epidermis in the hoof
Stratum externum Stratum medium
Stratum internum
name the layers of the equine dermis in the hoof
Perioplic corium
Coronary corium
Lamellar corium
Solar corium
describ ethe function of laminae in the equine hoof
Laminae are finger-like protrusions of tissue. In the equine foot, there are 2 types of laminae: sensitive (dermal) laminae and insensitive (epidermal) laminae. These two types of laminae interdigitate with each other to form a bond that is responsible for holding the hoof wall onto the horse’s foot.
describ ethe function of laminae in the equine hoof
Laminae are finger-like protrusions of tissue. In the equine foot, there are 2 types of laminae: sensitive (dermal) laminae and insensitive (epidermal) laminae. These two types of laminae interdigitate with each other to form a bond that is responsible for holding the hoof wall onto the horse’s foot.
Viborg’s triangle-
marks surgical entry site for the guttural pouch
parasite
an organism that lives in or on an organism of another species (its host) and benefits by deriving nutrients at the other’s expense:
Definitive host
an organism which supports the adult or sexually reproductive form of a parasite.
intermediate host
an organism that supports the immature or non-reproductive forms of a parasite.
Paratenic host
paratenic host a potential or substitute intermediate host that serves until the appropriate definitive host is reached, and in which no development of the parasite occurs; it may or may not be necessary to the completion of the parasite’s life cycle.
Obligate parasite
obligate parasite (obligatory parasite) one that is entirely dependent upon a host for its survival.
Facultative parasite
an organism that may resort to parasitic activity, but does not absolutely rely on any host for completion of its life cycle.
Host specific parasite
a parasite specific to its host
Mechanical vectors
here are certain vectors where the parasites (germs) are attached to the outside of their body, such as in legs and thus transmit the germs or parasites from one host to another without involving any developmental stages of the parasites in their body.
Biological vectors
biological vector an animal vector in whose body the pathogenic organism develops and multiplies before being transmitted to the next host. mechanical vector an animal vector not essential to the life cycle of the parasite.
Endemic
regularly found among particular people or in a certain area:
Hyperendemic
exhibiting a high and continued incidence —used chiefly of human diseases hyperendemic malaria
Epidemic
widespread occurrence of an infectious disease in a community at a particular time:
Zoonosis
a disease which can be transmitted to humans from animals.
Anthropozoonosis
An infectious disease acquired by humans from vertebrate hosts of the causative agents. Examples are rabies and trichinosis.
Zooanthroponosis
The transmission of disease from humans to animals. Specifically it refers to diseases that are primary infections of humans but which can be naturally transmitted to animals. Examples include tuberculosis and human metapneumovirus.
Amphixenosis
A zoonosis that can be passed from humans to other species as well as being passed from another species to a human
Anthroponoses
refers to pathogens sourced from humans and can include human to non-human animal transmission but also human to human transmission.
Cyclozoonosis
A zoonosis that requires more than one vertebrate host (but no invertebrate) for completion of the life cycle
Metazoonosis
A zoonosis that requires both a vertebrate and an invertebrate host for completion of its life cycle; for example, the arbovirus infections of humans and other vertebrates
Saprozoonosis
A zoonosis, the agent of which requires both a vertebrate host and a nonanimal (food, soil, plant) reservoir or developmental site for completion of its life cycle
How do parasites affect the host?
Compete for nutrients Depress appetite Damage skin or internal organs Diarrhoea Liver failure Respiratory problems Increase chances of secondary infections Stimulate immune system so that the animal is more susceptible to disease
what are the groups of endoparasites
Protozoa
Nematodes
Cestodes
Trematodes
basic nematode life cycle
egg l1- free living l2- free living l3- free livivng l4- within host l5- within host adult reproduction- repeat
Hypobiosis
A stage of parasite larval dormancy where nematode parasite larvae escape harsh environmental conditions by remaining in the wall of the abomasums.
Inhibited development stage with mass emergence = longer PPP
No inhibited stage = shorter PPP
Environmental or external stimulus at free living stage?
Mass emergence
Examples:
Toxocara canis
Cyathostomins
Teladorsagia
basic cestode lifecycle
Adult
(within definitive host)- gravid proglottids shed
Embryophore
(in environment)- Ingested by intermediate host
Oncosphere
(within intermediate host)- Breaks through gut wall of intermediate host and travels to site to form a …
Metacestode
(cyst within intermediate host)- Remains within intermediate host until it is ingested by definitive host
Trematode Lifecycle
Eggs-Passed in faeces onto pasture Miracidium -Miracidium hatches Within intermediate host-Develop to sporocyst, rediae and cercariae Leave intermediate host Cercariae Metacercariae- Ingested by grazing animals Lifecycle – 5 months PPP – 3 months
Protozoa Eimeria Lifecycle (example)
Unsporolated oocyst-Nucleus divides - sporocysts
Sporolated oocyst
(infective)- Ingested – liberation of sporocysts and sporozoites within them…
Sporozoites-Penetrate gut wall cells and reproduce asexually…
1st generation merozoites-Gut cells burst when full of 1st gen merozoites…
2nd generation merozoites-Invade more gut cells…Gut cells burst when full of 2nd gen merozoites…
Male / female -Fuse = oocysts!
Transmission of parasites
Faeco-oral Grazing, bedding, coat, Fungi Intermediate host Paratenic hosts
Pre-Patent Period
Time taken from ingestion of eggs/ larvae/ cysts to eggs being present in faeces
Ectoparasite groups
Arachnids: Mites Ticks 2. Insects: Flies Lice Fleas
Arachnid Lifecycle
egg
larvae
nymph
adult
insect lifecycle
Gravid female lays eggs
Eggs hatch - larvae- 12 hours
Larvae feed, grow and moult - maggots-Moult 3 times in 3-10 days
Maggots drop to ground and pupate– Pupate for 3 -7 days
(may overwinter)
Effects of ectoparasite infestation
Irritation / annoyance
Damage to skin / hide / fleece
Bites / wounds (painful!) and possibly anaemia if blood sucking
Disease transmission – vectors and 2ndry bacterial infections
Allergic reactions to saliva / faeces of ectoparasites
Myiasis
Creating a control plan for parasites
Need to know:
Which parasites are present, any resistance?
Perform faecal egg counts
Times of year those parasites cause problems
Best time to treat against them or use management to avoid them
e.g. Nematodirus, fluke, midges,
Which management strategies apply
Which chemicals are effective against the parasites that are present
Fleas.
Fleas are the most clinically important ectoparasites of dogs and cats worldwide with as many as 1 in 4 cats and 1 in 7 dogs infested.
Approximately 11% of fleas are infected with potentially pathogenic bacteria.
Fleas are wingless insects with laterally compressed bodies.
They have six legs that are well adapted for jumping.
Their size varies with species but, on average, is around 2 mm long.
Two of the most common companion animal fleas are -
Ctenocephalides felis (cat flea) - the cat flea is the most common in the UK and infests the cat, dog, rabbits, ferrets, small rodents and man.
Ctenocephalides canis (dog flea) found on some dogs in the UK and most common flea on dogs in Ireland. Diagnosis of fleas.
Finding adult fleas on the host - can be quite difficult to find a flea on the host as they move through hair very quickly.
Often flea faeces are the only sign of their presence.
Flea infestation has a variety of presentations determined by a number of factors.
However, there are two main presentation types depending on whether or not the host is sensitised to allergens present in flea saliva.
Non-hypersensitive animal – this animal is not allergic to the flea saliva and so the clinical signs can be moderate.
Presence of fleas and flea faeces.
Anaemia in severe cases.
Kill the adult flea on the host.
Kill the developmental stages in the environment.
scientific name of human and pig flea
Pulex irritans
scientific name of rabbit flea
Spilopsyllus cuniculi
scientific name of hedghog flea
Archaeopsylla erinacei
scientific name of bird related flea
Ceratophyllus gallinae
scientififc name of rodent flea
Nosopsyllus fasciatus
scientific name of cat flea
Ctenocephalides felis
scientific name of dog flea
Ctenocephalides canis
flea bite allergy
Pruritus (itchiness)
Self-trauma
Crusting
Truncated hairs
Alopecia
Cats – miliary dermatitis
Significance of fleas as vectors of disease.
Besides the direct effects resulting from blood feeding, Ctenocephalides species are important as vectors for a wide range of pathogens, many of which are zoonotic, for example -
Yersinia pestis (plague),
Rickettsia typhi (flea borne typhus in humans),
Rickettsia felis (flea borne spotted fever in humans),
Rickettsia conorii (boutonneuse fever in humans),
Bartonella henselae (cat-scratch disease in humans)
Fleas also act as intermediate hosts for cysticercoid larvae ofDipylidium caninumtapeworms.
Lice.
Lice are small wingless insects which can occur in large numbers on many companion animal species including dogs, cats, guinea-pigs and rabbits.
Lice are generally host-specific so lice infestation of one host species does not pose a risk for other species of host.
There are two main types of louse - sucking and chewing.
The “sucking lice” have a pointed head with a piercing proboscis, and feed regularly on blood.
Linognathus setosus (dog).
The “chewing lice” have a broad head bearing strong chewing mouth parts and feed on epidermal scales, scurf and wool.
Trichodectes canis (dog). Felicola subrostratus (cat). Significance of lice infestation -
Heavily louse infested animals can show severe pruritus, hair loss, skin thickening and scurfiness.
Severe cases can result in weight loss and anaemia.
Treatment.
Re-infestation can best be prevented by ensuring that treatment of the host is effective.
As lice do not live well off the host, transmission is usually by direct contact.
Several products available, including spot-ons.
scientific names of suckcing lice
Linognathus setosus (dog).
scientific names of chewing lice
Trichodectes canis (dog). Felicola subrostratus (cat
guinie pig lice
Gliricola porcelli and Gyropus ovalis.
mouse lice
Polyplax serrata
rat lice
Polyplax spinulosa
rabbit lice
– Haemodipsus ventricosus.
Ticks.
Ticks are arachnids.
They have, as adults, eight legs and are flattened dorsoventrally with a hard shield on the back.
They have no wings.
The ticks most commonly found on dogs and cats in the UK belong to the genusIxodes(I. ricinusandI. hexagonusare the most common, butI. canisugaand occasionallyI. frontalisandI.triangulicepshave been seen).
Dermacentor reticulatusandHaemaphysalis punctataand importedRhipicephalus sanguineusare occasionally found on pets.
I. ricinus is a three-host tick and the life cycle requires three years.
The tick feeds for only a few days each year, as a larva in the first year, a nymph in the second and an adult in the third.
The main importance of ticks is their role as vectors of pathogenic agents which cause a range of tick-borne diseases.
Some pathogens can be transmitted between different tick generations and/or life cycle stages, and some may thus be transmitted by every life cycle stage during feeding via salivary fluid.
Pathogens potentially transmitted by ticks include, Babesiaspp.,Borrelia burgdorferisensu lato,Hepatozoon canis,Acanthocheilonema (Dipetalonema)spp.,Bartonellaspp.,Ehrlichiaspp.,Anaplasma phagocytophilum,A. platys,Rickettsiaspp., flaviviruses and others can all be transmitted by ticks.
Lyme disease (caused by spirochaete bacteria Borrelia burgdorferi) is of particular relevance as a zoonotic disease in the UK.
Tick infestation can also be associated with secondary bacterial infection.
They may predispose to fly strike and in rare cases the blood sucking may lead to a degree of anaemia.
Removing ticks inappropriately can lead to tick granulomas.
Physical removal – tick hook.
Several products available including collars and spot-on preparations.
Mites
There are a wide range of companion animal mites.
The entire life cycle of the mite takes place on the animal or within its skin, but many of the stages can remain infective for several days off the animal.
Thus, direct animal to animal contact is not always necessary for transmission.
Otodectes cynotis
(ear mites).
These are commonly found in the dog and cat.
Clinical Signs - ear mites can occur in any age group of cats or dogs but are more common in puppies and kittens and more frequent in cats than dogs.
Whilst ear mites may be tolerated without clinical signs in some animals, especially cats, there may be a history of pruritus with ear scratching or rubbing and self-inflicted trauma.
Diagnosis - identification of characteristic brown ear wax similar in consistency to ground coffee, and mites in the external ear canal using an otoscope.
Cheyletiella.
Often referred to as fur mites.
Cheyletiella yasguri most common in the dog and Cheyletiella blakei in cats.
The entire life cycle takes approximately three weeks and is spent on the host, although female mites can survive for up to ten days in the environment.
Transfer from host to host occurs readily and rapidly between animals in close contact and cheyletiellosis is common in kennels with young and weak animals being more susceptible.
Clinical Signs - may be well tolerated in some animals with excessive scaling being the only clinical sign, while in other animals pruritus in variable degrees may be present.
Humans may also be infested, particularly around the waist and arms.
Diagnosis – coat brushings or strips.
Demodex
Demodex canis in dogs and Demodex cati in cats.
Demodex lives in hair follicles and sebaceous glands
In dogs there are two types of canine demodicosis –
Canine Localised Demodicosis (CLD) - defined as having up to five lesions, tends to present as one or several small, circumscribed, partially hairless patches, mainly on the face and the forelegs, is generally non-pruritic and spontaneously resolves.
Canine Generalised Demodicosis (CGD) - defined as six or more localised lesions, entire body regions affected such as feet.
Depending on the underlying condition, it may resolve spontaneously, but in most cases requires treatment, otherwise it may develop into a severe debilitating disease.
The adult-onset form of CGD usually occurs in dogs older than 4 years of age and although it can be very severe, it is rare.
Demodicosis is rare in cats and usually occurs as a localised form with alopecia confined to the eyelids and the periocular region, however, sometimes a generalised form will develop.
Diagnosed via deep skin scrapings or hair plucks.
Notoedres cati
Occurs mainly in cats.
Although infestation withN. catihas been reported from all European countries it is rare in some and tends to be local in distribution in others.
Cat notoedric mange is only exceptionally and transiently zoonotic.
Life Cycle - similar to that ofS. scabieiin that it is spent entirely on the host in tunnels in the upper layers of the skin.
Notoedric mange is highly contagious and is transmitted by close direct or indirect contact.
Clinical Signs - local areas of hair loss and erythema on the edges of the ears and the face, followed by greyish-yellow, dry crusting and skin scaling, which progresses to hyperkeratosis with thickening and wrinkling of the skin in severe cases, intense pruritus and scratching leading to excoriation and secondary bacterial infections.
Occasionally humans in contact with affected animals may show a mild dermatitis due to a transient infestation.
Sarcoptes.
The genusSarcoptescontains a single species,Sarcoptes scabiei, which causes sarcoptic mange in a wide range of mammalian hosts, but strains have developed which are largely host-specific with the possibility of temporarily infesting other mammals.
Sarcoptic mange mites are small, round parasites (up to 0.4 mm in diameter) which spend their entire life cycle on the host, so transmission is mainly through close contact.
They burrow in the superficial layers of the skin.
Transmission to new hosts from infested individuals is by direct or indirect contact, most likely by transfer of larvae from the skin surface - It is known thatS. scabieican survive for several weeks off the host.
S. scabieivar.caniscan be highly prevalent in the fox population.
Clinical disease in humans after contact with affected dogs is common.
The first visible signs are small nodules and pustules, as well as increased scaling.
Pruritus.
Alopecia.
Thickening and wrinkling of the skin occurs.
Intense pruritus leads to constant scratching.
Extensive excoriation and secondary bacterial infections are common.
The degree of pruritus may be exacerbated by the development of hypersensitivity to mite allergens.
Without treatment the disease progresses and lesions spread across the whole skin surface - dogs may become increasingly weak and emaciated.
Harvest Mites.
Harvest mites (Neotrombicula (Trombicula) autumnalis), are responsible for the condition known as trombiculosis.
Uncommon and characterised by their seasonal nature (July and August).
Only the larvae are parasitic and they do not transfer from animal to animal.
Harvest mites are resistant to adverse climatic conditions and female mites can live for more than 1 year.
Clinical Signs - cutaneous lesions are usually found in ground-skin contact areas like the head, ears, legs, feet, and ventral areas and the lesions are highly pruritic.
Control – spot-on preparations available although control is difficult due to the fact that reinfestations are frequent in animals exposed to these mites.
Tapeworm – general features.
Flattened, tape-like segmented body.
Each segment is self-contained, containing one or two sets of male and female reproductive organs.
The end segment is released from the tip of the tail and can pass out in the faeces.
This contaminates the areas where the animal defaecates.
Tapeworms have an indirect lifecycle requiring an intermediate host where the larval stages develop.
Larval forms usually encyst within the tissues of the intermediate hosts and primary control measures therefore include preventing exposure to intermediate hosts, where possible.
Dipylidium caninum.
Primary host is the dog or cat.
Intermediate host is the flea.
The adult tapeworms live in the intestines, eggs develop in the segments (proglottids). segments are shed from the tail of the tapeworm and are then passed out with the faeces into the environment.
The segments (proglottids) can often be seen around the affected animal’s perineal/anus area - often described by owners as “grains of rice”.
Eggs ingested by flea larva (intermediate host) and cyst develops in the flea body cavity containing developing forms of the tapeworm.
Flea ingested by primary host.
Taenia tapeworms.
Primary host - most commonly cats but also dogs.
Intermediate host – birds, small mammals etc (prey of hunting cat).
The adult tapeworm is found in the small intestine of the final host, segments and eggs reach the exterior in the faeces, egg is ingested by the intermediate host.
Once in the intermediate host, egg hatches and the embryo moves into the blood, lymph or (in invertebrates) the body cavity.
The embryo then moves to its predilection site in the host, which can be lungs, brain or muscle.
Once in its predilection site the embryo develops into its larval stage (cyst).
Intermediate host ingested by primary host.
Taenia taeniaeformis, the species that occurs in cats, uses rodents as intermediate hosts and dogs or cats are infected when they eat tissues or viscera of infected hosts.
Usually well tolerated in dogs and cats, potentially some anal irritation due to motile segments.
Echinococcus granulosus
Primary host – dog.
Intermediate host – the usual intermediate host is sheep however, any mammal in contact with dogs can become an intermediate host, including man (zoonosis).
The adult tapeworm is found in the gut of the dog, contamination of the environment occurs through the dog defaecating (eggs can survive in the environment for about a year).
Eggs are ingested by the intermediate host and encyst within the body (hydatid disease).
Cysts develops in lung, liver and body cavity containing developing forms of the tapeworm (hydatid disease).
Dog becomes infected by eating the intermediate host.
Echinococcus multilocularis.
Zoonotic tapeworm causing alveolar echinococcosis in humans that results in high fatality.
The definitive hosts are canids, mainly the red fox although domestic carnivores (dogs and to a lesser extent cats) can also be infected with the parasite.
Voles act as intermediate hosts.
The mandatory tapeworm treatment within the PETs scheme prior to entry into the UK is designed to prevent its entry.
Roundworms.
Roundworms have no segments and tend to be of a whitish or pinkish brown colour.
Prolific egg-layers and just a few worms can produce large numbers of eggs.
Toxocaraspp. eggs can survive in the environment for months or even years.
Toxocara canis in zoonotic roundworm in dogs
Toxocara cati in zoonotic roundworm in cats
Toxascaris leonina - zoonotic roundworm in cats and dogs
Dogs and cats can become infected from a number of sources including -
Picking worm eggs up from grass or soil in public places.
By ingesting a paratenic host.
Pregnant bitches can pass infection to their puppies both in utero and via the milk.
Pregnant queens can pass infection to their kittens via the milk (but not in utero).
Toxocara clinical signs
Affected animals often appear normal with a light infection.
Heavy infestation may cause cachexia and a pot-bellied appearance In kittens and pups alongside cachexia and gastrointestinal dysfunction.
Migrating larvae through the lungs can cause pneumonia associated with respiratory signs such as coughing.
Retinal dysfunction may occur in dogs due to migrating larvae, although it does not usually affect the animal’s normal functioning, lesions may be seen on examination of the retina.
Lungworm.
There are many different lungworm parasites whose adult stages occur in different anatomical areas within the respiratory tract of the host.
Lungworms are prevalent throughout the UK and Europe and can be transmitted directly from host to host or via intermediate hosts, depending on the species.
Angiostrongylus vasorum
Commonly known as “Lungworm” (or French Heartworm) in the UK.
A. vasorumis now endemic in much of the UK.
Slugs and snails act as intermediate hosts, although dogs may also acquire infection through ingestion of frogs and other amphibians acting as paratenic hosts.
Clinical signs –
Early infections - coughing, dyspnoea, anaemia, depression, anorexia, and signs of coagulopathy e.g., melaena, haemoptysis, prolonged bleeding from minor injuries and subcutaneous haematomas may be seen.
Severe infections - right sided heart failure and sudden death may occur and in chronic infection, verminous pneumonia can develop leading to anorexia and weight loss, emaciation and pulmonary hypertension.
Occasionally larvae and rarely adult stages ofA. vasorumare located in ectopic locations such as brain, bladder, kidney or the anterior chamber of the eye.
Hookworms
Hookworms are small nematodes characterised by large mouthparts that are at an angle to the rest of the worm, hence the common name.
There are three species of significance in Europe –
Ancylostoma caninum,
Ancylostoma tubaeforme
Uncinaria stenocephala (most common in UK).
Life cycle - All hookworms demonstrate a direct life cycle - eggs passed in the faeces, once ingested develop within 2-3 weeks to adult worms.
Ancylostomaspp. larvae are capable of penetrating skin and thus making their way to the intestine.
Clinical signs - anaemia in a heavy infection is possible with A. caninum and A. tubaeforme butU. stenocephala normally shows no clinical signs.
Control – prompt removal of faeces and disposal will help to prevent larvae developing on grass, however regular worming to controlToxocaraspp. will usually also control hookworms.
Whipworms.
Eggs are passed in the faeces of infected dogs and can lead to considerable and persistent contamination of the environment.
First stage larva protected by the egg shell and can survive in the environment for years.
Dogs are infected when they eat eggs containing infective larvae - pre-patent period is 2 - 3 months and infected dogs may continue to shed eggs for up to a year.
Clinical signs - light infection is well tolerated, however a heavy infection will result in diarrhoeic bloody, mucus-filled faeces.
Control - depends on removing dogs where possible from the contaminated environment and repeated anthelmintic treatment (regular worming to controlToxocaraspp. will also control hookworms so long as a treatment with an appropriate spectrum of activity is selected.)
Prompt removal of faeces and disposal will help to prevent eggs developing in the environment.
Compact bone
Compact bone stands in stark contrast to trabecular bone in several ways. The functional units of compact bone are osteons; which contain a centrally located Haversian canal, encased in lamellae (concentric rings). Osteocytes can be observed in the lacunae between the osteons. The osteons – unlike the trabeculae – are densely packed, making compact bone tougher and heavier than spongy bone. The Haversian canals facilitate passage of blood vessels supplying the developing bone.
Osteons
cylindrical structures that contain a mineral matrix and living osteocytes connected by canaliculi, which transport blood. They are aligned parallel to the long axis of the bone. Each osteon consists of lamellae, which are layers of compact matrix that surround a central canal called the Haversian canal. The Haversian canal (osteonic canal) contains the bone’s blood vessels and nerve fibers (Figure 1). Osteons in compact bone tissue are aligned in the same direction along lines of stress and help the bone resist bending or fracturing. Therefore, compact bone tissue is prominent in areas of bone at which stresses are applied in only a few directions.
Spongy bone
spongy bone is comprised of anastomosing strips of slender bone known as trabeculae that enclose marrow and blood vessels. It forms the relatively softer core of the bones that is filled with marrow.
The less densely arranged trabeculae also contribute to making the bones lighter (as opposed to the heavier compact bone). Communication between adjacent cavities is achieved by canaliculi. Although the trabecular network makes the bone lighter, and increases the available space to house marrow, the arrangement also provides reinforcement for the bone, making it stronger.
Skeletal muscle
excitable, contractile tissue responsible for maintaining posture and moving the orbits, together with the appendicular and axial skeletons. It attaches to bones and the orbits through tendons. Excitable tissue responds to stimuli through electrical signals. Contractile tissue is able to generate tension of force.
Skeletal muscle tissue is also extensible and elastic. Extensible tissue can be stretched and elastic tissue is able to return to its original shape following distortion.
Sarcoplasm
cytoplasm of a muscle cell
sarcolemma
Plasma membrane of a muscle cell
sarcoplasmic reticulum.
Endoplasmic reticulum of muscle cell
myofiber
A muscle fiber
Sarcomeres
The sarcomere is the functional unit of a skeletal muscle cell. Each sarcomere is about 2.5 micrometers in length. It is made up of multiple myosin and actin filaments oriented in parallel. The actin and myosin filaments overlap in certain places creating several bands and zones. A Z disc forms the boundary of the sarcomere on either side. Thin actin filaments project in either direction off of a Z disc but do not cross the entire length of the sarcomere. They are almost 8 nm in diameter and have tightly bound regulatory proteins called troponin and tropomyosin.
The center of the sarcomere lacks actin filaments and is referred to as the H zone. An M line runs down the middle of the H zone perpendicular to the filaments. Thick myosin filaments are found between the actin filaments. Their diameter is approximately 15 nm with a globular head region consisting of heavy and light chain. This head has an ATPase activity and ability to bind and move along actin filament. They are not connected to the Z discs but do traverse the H zone.
The sarcomere is broken up into three bands. The A band is in the middle and corresponds to the myosin filaments together with the thin filaments overlapping on both ends. There are two I bands on either side of the A band and represent the area in which only actin filaments are present.
Z disc
A Z disc forms the boundary of the sarcomere on either side. Thin actin filaments project in either direction off of a Z disc but do not cross the entire length of the sarcomer
H zone
The center of the sarcomere lacks actin filaments and is referred to as the H zone
M line
runs down the middle of the H zone perpendicular to the filaments.
A band
in the middle of the sacromere and corresponds to the myosin filaments together with the thin filaments overlapping on both ends.
I bands
I bands on either side of the A band and represent the area in which only actin filaments are present.
Tendon
Tendons are situated between bone and muscles and are bright white in colour, their fibro-elastic composition gives them the strength require to transmit large mechanical forces. Each muscle has two tendons, one proximally and one distally. The point at which the tendon forms attachment to the muscle is also known as the musculotendinous junction (MTJ) and the point at which it attaches to the bone is known as the osteotendinous junction (OTJ). The purpose of the tendon is to transmit forces generated from the muscle to the bone to elicit movement. The proximal attachment of the tendon is also known as the origin and the distal tendon is called the insertion.[1]
Tendons have different shapes and sizes depending on the role of the muscle. Muscles that generate a lot of power and force tend to have shorter and wider tendons than those that perform more fine delicate movements. These tend to be long and thin.
The tendon cells are known as tenoblasts and tenocytes. They make up approximately 90-95% of the cells within the tendon. The other 5-10% include the chondrocyctes, synovial cells and the vascular cells.
Articular Cartilage
Articular cartilage is the highly specialized connective tissue of diarthrodial joints. Its principal function is to provide a smooth, lubricated surface for articulation and to facilitate the transmission of loads with a low frictional coefficient (Figure 1). Articular cartilage is devoid of blood vessels, lymphatics, and nerves and is subject to a harsh biomechanical environment. Most important, articular cartilage has a limited capacity for intrinsic healing and repair. In this regard, the preservation and health of articular cartilage are paramount to joint health
dependent on the molecular composition of the extracellular matrix (ECM), which consists mainly of proteoglycans and collagen. As mentioned previously, the main proteoglycan in cartilage is aggrecan, which forms large aggregates with hyaluronan and are negatively charged to hold water in the tissue. The collagen (mainly type II), acts to constrain the proteoglycans and helps it hold its structure. Consequently, the ECM functions to respond to the tensile, shear, and compressive forces that are experienced by cartilage during mechanical use such as normal gait or weight-bearing movements.
Connective Tissues
Connective tissues provide support and protection for tissues and organs. It has three main components; cells, proteins and ground substance. The protein, which is often fibrous in nature, combined with the ground substance make up the extracellular matrix. Types of protein within the extracellular matrix are collagen fibres which provide tensile strength, elastic fibres which provide stretch and recoil and reticular fibres (comprising collagen III) which provide support. The ground substance is organic material surrounding these fibres.
There are many types of connective tissue including loose connective tissue, dense connective tissue, specialised connective tissue; adipose, cartilage, bone and blood and embryonic connective tissue
Cartilage
Cartilage can be found covering joint surfaces. The cells of cartilage are called chondrocytes, they sit in spaces called lacunae, figure 2. The lacunae are surrounded by extracellular matrix. Collagen fibres within the extracellular matrix provide high tensile strength whilst proteoglycans attract water. Note cartilage is avascular meaning it has no blood supply and nutrients are supplied by diffusion. This makes damage to cartilage difficult to heal
Elastic cartilage
like hyaline cartilage but contains elastic fibres to allow flexibility, it is found within the external ear, auditory tube and epiglottis
Fibrocartilage
– like hyaline cartilage but with additional collagen fibres to add tensile strength. Fibrocartilage is found in intervertebral disks and the menisci of the knee or stifle joint.
describe the control, apperence and location of skeletal muscle
volantary
striated
locomotor system
describe the conteol, apperence and location of cardiac Muscle
involuntary
straited
heart
describe the control, apperence and location of smooth muscle
involentary
non striated
vessels, lungs, gastrointestinal tract
Epithelia
An epithelium is a sheet of cells that covers external and internal parts of the body. The epithelium provides a protective barrier at the body’s surface. The epithelium can exhibit specialist features dependent upon its location within the body, for instance absorptive capability within the gastrointestinal tract.
Blood
Blood is a cellular fluid that transports nutrients and waste products around the body. It consists of a variety of cell types including red blood cells and white blood cells. The cells are surrounded by plasma
fundic stomach
Although the stomach does not have villi, the empty stomach has folds or ridges, called rugae, are formed from the mucosa and submucosa.
The wall of the fundic stomach is composed of the four layers characteristic of the gastrointestinal tract:
Mucosa - composed of the epithelium, lamina propria, and muscularis mucosae.
Gastric Pits - surface invaginations lined with surface mucous cells.
Fundic Glands - contain three major cell types:
Mucous Neck Cells - smaller, basophilic cells found in the isthmus and neck between parietal cells.
Parietal Cells - strongly eosinophilic cells with a large, oval shape and a central nucleus found mostly in the neck.
Chief Cells - basophilic cells located in the fundus.
Muscularis Mucosae
Submucosa
Muscularis Externa
Duodenum
The duodenum is the first of the three parts of the small intestine that receives partially digested food from the stomach and begins with the absorption of nutrients. It is directly attached to the pylorus of the stomach. It has a C-shape, it is closely related to the head of the pancreas and consists of four sections: superior, descending, horizontal, and ascending parts.
Histologically speaking, the duodenum consists of the typical three layers common to all hollow organs of the gastrointestinal tract, but it has Brunner’s glands, which is the characteristic feature of the duodenum
colon
The colon forms part of the large intestine and extends between the caecum and the rectum.
Histologically, the mucosa is lined by simple columnar epithelium and contains crypts of Lieberkuhn and numerous goblet cells.
The colon has the typical histological structure as the digestive tube: mucosa, submucosa, muscularis and serosa/adventitia. The mucosa is lined by simple columnar epithelium (lamina epithelialis) with long microvilli. It is covered by a layer of mucus which aids the transport of the feces. The mucosa does not contain villi but many crypts of Lieberkuhn in which numerous goblet cells and enteroendocrine cells are found.
liver
he liver consists of the following major histological components:
Parenchyma, which is represented by hepatocytes
Stroma, which is a continuation of the surrounding capsule of Glisson. It consists of connective tissue and contains the vessels. The capsule is also covered by a layer of mesothelium, arising from the peritoneum covering the liver. The connective tissue of the stroma is type III collagen (reticulin), which forms a meshwork that provides integrity for the hepatocytes and sinusoids.
Sinusoids, which are capillaries travelling between hepatocytes
Spaces of Disse (perisinusoidal spaces), which are located between the hepatocytes and the sinusoids
In histological terms, the liver consists of a large number of microscopic functional units that work in unison to ensure the overall, proper activity of the entire organ. There are three possible ways of describing one such unit, as given below:
Hepatic (classic) lobule
Portal lobule
Liver acinus
pancreas histology
he pancreas is both an exocrine accessory digestive organ and a hormone secreting endocrine gland. The bulk of the pancreatic tissue is formed by the exocrine component, which consists of many serous pancreatic acini cells
The endocrine component makes up about 2% of the pancreas, which is represented by about 1-2 million pancreatic islets (of Langerhans). They are dispersed throughout the exocrine component of the pancreas, most of them being located in the tail region. These islets are demarcated from the rest of the parenchyma by a delicate sheath of reticular fibers.
4 layers of the gut wall
1) The Mucosa (of which the epithelium is a part)
2) The submucosa
3) The tunica muscularis
4) Serosa (the outer most layer).
3 layers of the mucosa
The mucosa can be broken down into three further regions. The epithelium is the innermost one of these. Beneath this is the lamina propria and beneath this the muscularis mucosa (which may be present or absent depending on tissue and region), see figure 3. The muscularis mucosa is adjacent to the submucosa.
Glands are formed byz
clusters of secretory epithelial cells surrounding a lumen (into which they will secrete their products)
describe the histology of parieta cells
· Identify parietal and chief cells (parietal cells are larger cells staining pink/red, chief cells are smaller
describe the histology of cheif
larger cells staining pink/red, chief cells are small and stain darker).
What is the purpose of the villi?
The villi aid in absorption by increasing the surface area of the intestine and contain specialized cells which transport different types of nutrients into the blood.
What epithelium lines the villi?
The mucosa of the small intestine is lined by a simple columnar epithelium which consists primarily of absorptive cells (enterocytes), with scattered goblet cells and occasional enteroendocrine cells.
Sinusoids
specialised, fenestrated or leaky capillaries that lie between the lines of hepatocytes allowing easy diffusion between the hepatocytes and the blood.
describe the blood flow to the liver
. It receives nutrient rich deoxygenated blood from the gut, and oxygenated blood from the hepatic artery. Once inside the liver these major vessels branch many times to supply each and every hepatocyte. If external lobation is evident then a primary branch of each of the
hepatic portal vein and hepatic artery goes to each lobe. The smaller vessels then converge to drain back to the caudal vena cava.
The arrangement of the hepatocytes in relation to the blood supply and bile canaliculi is vital to the function of the liver. Easy exchange between the blood, the hepatocytes and the bile canaliculi is essential for liver function. A collection of hepatocytes and vessels form a liver lobule. The lobules are not easily identified by the naked eye but give rise to a mockled appearance of the liver
portal triad
The artery has a thicker wall relative the vein and is round if cut in true cross section. The vein will have a thinner wall and may be more irregularly shaped. The bile duct has columnar epithelium, and can modify bile by adding water, electrolytes and bicarbonate
bile
Hepatocytes form bile acids from cholesterol in the smooth endoplasmic reticulum. These bile acids have hydrophilic and hydrophobic regions giving them bile its detergent properties. However, bile contains more than just bile acids. As bile acids are released from the cell they take with them some of the phospholipids and cholesterol from the cell membrane. Upon secretion bile acids are attached to sodium and so are called bile salts, this has the effect of drawing water from cells of the duct wall into the bile. Other components of bile include bile pigments such as bilirubin, (a product of red blood cell turnover and that which give bile its green colour). These pigments are non- functional and just use bile as a means of excretion from the body. Drugs and toxins may also be excreted through the liver due to the detergent nature of the bile that the liver secretes. Bilirubin levels may be tested to assess liver function.
Which direction does blood flow through the sinusoids
n the liver, blood enters the hepatic sinusoids from both the portal vein (q.v.) and the hepatic artery; the venous blood is cleansed in the sinusoids, while the arterial blood provides oxygen to the surrounding liver cells
Where are the portal veins in the portal triads coming from?
Venous blood from the intestinal tract enters the liver through the portal triad via the portal vein, mixes with well-oxygenated hepatic arterial blood within the sinusoids, and exits via the terminal hepatic (central) vein.
Which direction does bile flow through the canaliculi?
The bile canaliculi empty into a series of progressively larger bile ductules and ducts, which eventually become common hepatic duct. The bile canaliculi empty directly into the Canals of Hering.
describe stratified columnar epithelium
Protective, may be secretory,
found in Ocular conjunctiva
describe stratified cuboidal epithelium
protective, may be secretory
found in Lining large ducts from sweat, mammary and salivary glands
describe stratified squamous epithelium
protective
found in the oesophagus
describe transitional epithelium
impermeable, distendable
found in urinary bladder
describe the epithelium of the oesophagus now.
The thick epithelial layer lines the lumen of the esophagus and consists of stratified squamous non-keratinized cells, which has their typical appearance of flat, overlapping cells that are more flat as they move away from the base or basal cell layer.
describe the epithelium lining the stomach
he innermost layer of the stomach wall is the gastric mucosa. It is formed by a layer of surface epithelium and an underlying lamina propria and muscularis mucosae. The surface epithelium is a simple columnar epithelium. It lines the inside of the stomach as surface mucous cells and forms numerous tiny invaginations, or gastric pits, which appear as millions of holes all throughout the stomach lining. These gastric pits are important as they are connected to the various glands of the stomach.
Commensalism:
Least intimate of relationships where one or both species may benefit
Transport, cleaning, protection e.g. micro-organisms that live on skin,
Mutualism:
An association where both partners benefit
Protozoa in hind gut of horses and fore stomach of ruminants
Pathogenesis
the manner of development of a disease
Nematodes
Among the most ubiquitous of all animals:
Antarctic, hot springs, soil, fresh and salt water
Where there is a living organism there will be several nematodes to parasitize it!
any unsegmented worm of the phylum Nematoda, having an elongated, cylindrical body; a roundworm.
Cestodes
Indirect lifecycle
Hermaphrodites
Reliant on host – no free living stage
No mouth / anus – absorb pre-digested nutrients through tegument a parasitic flatworm of the class Cestoda, which comprises the tapeworms
Trematodes
Liver and stomach flukes
Indirect lifecycle - snails
Hermaphrodites
Paedogenesis - production of many new individuals from a single larval form
Any of numerous parasitic flatworms of the class Trematoda, having a thick outer cuticle and one or more suckers or hooks for attaching to host tissue.
Paedogenesis
production of many new individuals from a single larval form
Protozoa
Single celled organisms
50,000 known species
Only one fifth (10,000) of these are parasitic
Important groups in terms of animal health:
Eimeriidae (Eimeria spp. and Isospora spp.)
Cryptosporidium
Sarcocystidae (Toxoplasma, Neospora)
Babesiidae (Babesia)
Periparturient Rise of parasites
Temporary relaxation of female host’s immunity around time of parturition (4 wks before up to 8 wks after)
Decreased immunity to parasites:
Hormonal interactions
Stress
Nutritional stress in late pregnancy and early lactation
Treatment and control of parasite
Predominantly chemotherapy Resistance Environmental concerns Residues Sustainable alternatives?
chemical treatments for nematodes
Anthelmintics - various applied via oral, pour-ons, spot-ons,
chemical treatments for cesodes
Oral praziquantel or double dose pyrantel applied orally
chemical treatments for trematodes
Triclabendazole,
Closantel, Nitroxynil,
Albendazole, Oxyclozanide
applied oraly
chemical treatments for protozoa
Sulphonamides applied orally
Avoiding Anthelmintic Resistance
Excessive, frequent dosing Under-dosing Accurately assess weight -correct dose given Dose for heaviest animal Ensure full dose is administered Drenching technique Rotate chemical groups annually Some drenches are more effective on empty gut – read the instructions! Treat at right time of year Treat all new animals on arrival Do faecal egg counts
Reducing incidence of parasitisim
Breed for resistance Graze on bioactive forages e.g. chicory, birdsfoot trefoil, Stocking rates Rotational grazing Mixed species grazing, mixed age grazing
Dung lifting / removal / pick up poo
Harrowing
Monitor consumption of potential intermediate hosts
Prevent scavenging
Keep bedding and environment clean, dry, fresh
Treat new arrivals before mixing with other animals
determining parasite infection
Faecal examination or egg count Post-mortem Antibody tests Blood Saliva
Effects of ectoparasite infestation
Irritation / annoyance
Damage to skin / hide / fleece
Itching, shaking, bleeding, smell, hair loss / alopecia, infection,
Lesion damage predisposes to blowfly (another ectoparasite!)
Seasonal itching
Bites / wounds (painful!) and possibly anaemia if blood sucking
Disease transmission – vectors and 2ndry bacterial infections
Allergic reactions to saliva / faeces of ectoparasites
Myiasis = Infestation of a living animal with larvae of dipteran flies
Blowfly strike
Eggs laid on host
Larvae hatch and feed on host skin
Additional risk of vector-bourne diseases:
Protozoa e.g. Babesia,
Bacteria e.g. Rickettsia, mastitis, conjunctivitis, Bartonella henselae
Viruses e.g. Louping ill, feline leukaemia virus
Endoparasites
Which endoparasite is transmitted by common insect ectoparasites of dogs and cats?
control of Ectoparasites
Dipping Showers Weekly bathing with specific product Spot ons and Pour ons Injectables Isolate affected animals Remove eggs – comb, insecticide Dress lesions with appropriate insecticide Tailing, dagging Endoparasite control Remove manure from grazing and housing areas to remove insects Manure heap fermentation Temperature kills eggs and larvae
Remove breeding sites such as stagnant water or remove animals from breeding area
E.g. Tick survival dependent on tick’s requirement for water
Must have relative humidity greater than 90%
Common in wetter, marshy areas
E.g. Mosquitoes eggs laid in standing water
Larvae live in standing water
Insecticide or repellent impregnated ear tags, tail bands and halters
Screens to prevent insect access to housing
Electrocution grids to kill insects within housing
Fans to affect flight
Wash and treat all bedding, grooming tools, equipment, rugs,
Or leave unused for 3 weeks
Helminths
Trematodes, cestodes, nematodes
host specific life cycle
Reduced productivity from clinical and sub clinical disease
dormant and free living stages
Zoonotic risk: control=meat hygiene inspection
Body system affected-primarily alimentary
Life cycle-ingestion of infected larvae on food and disseminating pre-infective stages in faeces onto food/pasture
infective strategy of helminths
Infective strategy:
The effect of the infection is determined mainly by
varying susceptibility of the host species,
Pathogenicity of the parasite species,
host/parasite interaction,
infective dose
Emerging issues
Resistance to drugs!
The level of control vary from region to region
depends to a large extend upon religious and socio-economical considerations,
inclusive the organisational infrastructure of the society
Trematode-liver fluke
helminth
Fasciola hepatica (cattle)
Dicrocelium dendriticum (sheep)
Body system affected- alimentary: liver
Highly pathogenic
Acute-Sudden death or dullness, anaemia, dyspnoea, ascites and abdominal pain
Subacute-Rapid weight loss, anaemia, submandibular oedema and ascites in some cases.
Chronic-Progressive weight loss, anaemia, submandibular oedema, diarrhoea and ascites
Treatment options
Drugs (resistance seen)
Move onto lower risk pasture
infective strategy of Trematode-liver fluke
Galba truncatula snail
-Wet pasture
Trematode: stomach fluke ‘Rumen fluke (helminth)
Paramphistomium Calicophoron daubneyi
Body system affected- alimentary: rumen
Life cycle-similar to liver fluke, however once in the definitive host:
After excysting in the small intestine, the tiny immature rumen fluke migrate ‘upstream’ and settle in the rumen and reticulum, where they mature and lay eggs.
Infective strategy: Galba truncatula snail
Pathogenesis: generic
Diagnostic methods:
faecal egg count (FEC) by sedimentation,
PM,
meat inspection
Treatment options-advice not to treat, limited drugs available
Emerging issues: only identified in the UK last 20 years,
cestodes (helminths)
Taenia saginata, T.solium, T. Ovis, T.multiceps
Echinococcus multilocularis, E. granulosus
Body system affected- alimentary and muscle
Life cycle-indirect, intermediate host (humans are the definitive host)
Infective strategy: rely on poor meat cooking and hygiene
Pathogenesis-low, little disease for animals
Diagnostic methods:
faecal worm egg count for ova,
direct faecal assessment for proglottids,
ELISA,
meat inspection,
PM
Treatment options- drugs
Emerging issues
Nematodes: Trichostrongyles (helminths)
Ostertagia ostertagi (abomasal), Telorsagia cercumsincta (abomasal), Dictyocaulus spp (respiratory &alimentary), Haemonchus spp (abomasal), Nematodirus spp (small intestine), Trichostrongylus spp
Life cycle-direct Infective strategy –need infective pastures, critical temperatures, periparturient rise in production, hypobiosis Pathogenicity varies genera and species, numbers of nematodes age (maturity) nutritional status body condition Diagnostic methods: FWEC but will give false negative in early stages of disease due to lack of mature egg producing parasites. Treatment options-drugs, grazing management control, lung worm vaccine Emerging issues-drug resistance Nematodirus battus
Slightly different life cycle
Nematodes: Strongyles
heminths
Cyathostomins, Chabertia (colon), Oesophagostomum (colon)
Body system affected- alimentary
Life cycle-simple, non migratory
Pathogenesis-no clinical significance unless concurrent disease
Diagnostic methods-FWEC
Treatment options-drugs
Nematodes: Hookworms
helminths
Bunostomum spp
Body system affected- small intestine or colon
Life cycle-direct
Infective strategy-orally or percutaneously through the feet
Pathogenesis-blood feeders
Diagnostic methods-FWEC
Treatment options-drugs and hygiene
Emerging issues-zoonotic, with poor human immune response
Nematodes: Ascarids
helminths
Ascaris suum, Trichinella spp,
Body system affected- small intestine, liver, lung
Life cycle-direct
Infective strategy-infective L3 and arrested development.
Migratory or non-migratory
Pathogenesis-Milk spot liver in pigs
Diagnostic methods-PM, meat inspection
Treatment options-drugs, hygiene
Emerging issues-increasing numbers of outdoor sows so more difficulty in eliminating them from a premises.
Protozoa: Sporozoan
Coccidia (Eimeria spp)
Causes Diarrhoea in calves and lambs
alimentary-small intestine in sheep, caecum and colon in cattle
Life cycle:direct, highly host specific
Causes diarrhoea in calves under a year old and lambs 1-2months old
-each host can be infected by a number of different Eimeria spp
Reside in the small intestine in sheep,
Caesium and colon in cattle
-Infective strategy:lambs infected by chronically infected adults which shed oocysts, the lambs then produce large numbers of oocysts to infect others. The sporulated infective oocyst contains 4 sporocysts each containing 2 sporozoites (8sporozoites/sporulated oocyst)
Pathogenesis: 11 species infect sheep but only 3 are pathogenic, 13 infect cattle but only 2 are pathogenic
Diagnostic methods: Faecal worm egg counts for coccidial oocysts
Treatment options:
Drugs to treat and prevention
Environmental action
Feed off the floor Improve hygiene
Lower stress levels
Low numbers in FWEC can be normal ‘background’ levels, only concerned when get high numbers over 5000 per gram
In feed medication
Oral drenches
Need to get some exposure to gain immunity
Protozoa: Sporozoan
Cryptosporidium parvum
Causes diarrhoea in young calves and lambs
Body system:small intestine
Life cycle:direct
Infective strategy:
Pathogenesis: as the oocysts grow they disrupt the brush border, decreasing absorption of fluids from the lumen
Causes diarrhoea in young calves and lambs, 2-4weeks old
it develops at the junction between the micro-villous brush border and the cytoplasm gut epithelial cells. It produces very small (~4mm) sporulated oocysts which either initiate another cycle of asexual reproduction in the same host or are shed from the body via the faeces
Diagnostic methods:
SNAP test for crypto,
faecal smear after Giemsa stain;
Identification of organism in stained gut sections of post mortem
Treatment options:
Drugs to treat and prevention
Environmental action
Control other diarrhoea pathogens
Colostrum management
Emerging issues:important cause of food poisoning in humans from contaminated water sources or meat. High risk pathogen for immunosuppressed people
As well as causing disease in its own right, Crypto is an opportunistic pathogen and loves to tag onto the back of rotavirus infections when the intestinal lumen is already damaged, further damaging the intestine causing much more severe diarrhoea
Hygiene, cleaning, drying and disinfecting equipment used to feed and house young
Good colostrum management
Protozoa: Sporozoan Iospora spp (very similar to coccidiosis)
Usually non pathogenic but in high levels Causes enteritis in piglets
affects the small intestine causing diarrhoea, dehydration, and loss of electrolytes, perhaps death
Life cycle:direct
Infective strategy: they have 2 sporocysts per oocyst each containing 4 sporozoites
Pathogenesis:As for cocci
Diagnostic methods: as for coccidiosis, BUT do not confuse these oocysts with the more zoonotically important Toxoplasma
Treatment options:
Drugs to treat and prevention
Environmental hygiene
confinement-raised, one to three week old, nursing piglets and is less frequent and severe in older recently weaned piglets.
Oocysts become infective in about 12 hours. After ingestion of sporulated oocysts, patency in neonatal pigs can occur in as little as five days.
Isospora suisgoes through the usual stages of sporogeny, excystation, and endogenous development with multiplication in intestinal epithelium as is reported in other species. Development usually occurs in epithelium of the small intestine, especially in the jejunum and ileum, less often in the duodenum, cecum and colon. Development usually occurs in the cells on distal portions of intestinal villi; in severe infections it may occur in cryptal epithelium. Fully sporulated oocysts ofI. suishave two sporocysts; each of these has four sporozoites.
development of coccidia in enterocytes results in desquamation of enterocytes, especially those on the distal tips of villi.
The severity of lesions is related to the number of oocysts ingested. Bacteria in the intestine, including Clostridium, may contribute to overall severity of the lesions. When many coccidia are ingested, lesions are severe.
In serious infections, the erosion of villous epithelium results in loss of fluid and failure of surviving epithelium to absorb nutrients and fluids. This leads to diarrhea, dehydration, and loss of electrolytes, perhaps death
Protozoa: Sporozoan
Sarcocyst
Causes abortion and meat condemnation in sheep and cattle
Causes abortion & congenital abnormalities in humans
Body system affected- alimentary and reproductive
Life cycle: indirect, specific pairings of intermediate and definitive hosts
Over 250 types: Species-specific prey-predator life cycles
After ingestion of sporocysts by a suitable intermediate host, sporozoites are liberated and initiate development of schizonts in vascular endothelia of mesenteric arterioles and lymph nodes. A second generation of endothelial schizonts is produced in capillaries from several organs. Merozoites released from these schizonts invade the muscle fibers and develop into the typical sarcocysts
Natural infections are usually asymptomatic. However, experimental infections withS cruzisporocysts cause acute disease in calves; eosinophilic myositis in cattle; and abortions, stillbirths, and deaths in pregnant cows. Cases of necrotic encephalitis and fatal myocarditis in heifers have been reported. Similar pathogenicity has been demonstrated forS tenellain lambs and ewes and forS miescherianain pigs. An outbreak of myositis affecting 20 ewes with flaccid paralysis was a result of heavySarcocystisinfection.
Immune status of the host and the dose of sporocysts may be the most important factors for development of clinical disease. Natural infections are assumed to occur frequently with low numbers of sporocysts, leading to chronic and asymptomatic infections
Pathogenesis:
Diagnostic methods: faecal flotation techniques.
Treatment options
No effective treatments
prevent ingestion of prey carcasses or raw tissues by omnivorous or carnivorous animals
Some drugs are used abroad as a prevention but are not licensed in the UK
Effective cooking or freezing kills the parasite in meat.
Protozoa: Sporozoan
Toxoplasma gondii
Body system affected- alimentary and reproductive
Life cycle: indirect, facultative heteroxenous
Infective strategy: capable of developing in almost any cell type
Clinical signs:
Barren to tup,
abortion,
mummification
stillbirth (occasionally one live lamb born with a dead lamb)
birth of weak lambs
White focal necrosis on the placenta
Definitive host is the adolescent naive cat who is infected by eating infected rodents, produce oocysts in their faeces before becoming immune.
Toxoplasmosis is caused by toxoplasma oocysts picked up from feed or hay, or off pasture that has been contaminated by cat faeces.
These oocysts are very resilient and can survive for very long periods in feed or on pasture
Once a ewe has been infected, she soon becomes immune and is unlikely to show signs of the disease in subsequent years. It is only when an infection is picked up for the first time during pregnancy that problems occur.The stage at which an infection is picked up during pregnancy will determine the outcome as there is an approximate six week lag period between infection and onset of clinical signs:First 60 days – foetus absorbed and the ewe appears barren.60 – 120 days – abortion in late pregnancy with mummified foetuses, stillbirths or weak and sickly lambs that often die.
There arefive main syndromes of abortion in sheep –
Barren to tup,
abortion,
mummification (particularly common with toxoplasmosis),
stillbirth (occasionally one live lamb born with a dead lamb)
birth of weak lambs which fail to suckle properly and often succumb to disease in young life.
It is howevercommon to have many or all of these syndromes on a farm at the same time.A clinical sign which is characteristic of toxoplasmosis abortion is the development of small white areas in the cotyledons (buttons) of the placenta. These are caused by focal necrosis (death of cells) in areas of the placenta due to damage caused by multiplication of theToxoplasmaorganism.
Protozoa: Sporozoan
Toxoplasma gondii
Diagnostic methods: Antibody serology Aborted foetal organ histopathology Treatment options: only an attenuated vaccine available, rodent control, neutering cats, retaining immune exposed/aborted ewes zoonosis – pregnant people Diagnosis: Antibody testingRetrospective diagnosis oftoxoplasma infection can be made by measuring antibody levels in serum samples. However as toxoplasma is ubiquitous in the environment, a titre to toxoplasmosis is not a definitive diagnosis that it is the cause of an abortion problem. Therefore antibody testing is of limited value in establishing a definitive diagnosis. However, testing of foetal heart blood from aborted foetuses is useful as a titre in an aborted foetus is quite a useful diagnostic indicator. Identification of the organismSamples that can be submitted for histopathology (examination under a microscope). These include a variety of foetal organs from the aborted material with the brain particularly useful. Characteristic pathology provides a definitive diagnosis
Treatment/control:
Retaining sheep in the flock after an abortion episode– Sheep that have aborted with toxoplasmosis are immune, probably for life.
Rodent control – As rodents provide an ongoing source of infection, an effective rodent control plan must be implemented on farm.
maintaining the farm cat population. However, it is useful to neuter all farm cats to avoid the production of further kittens that can act as a new source of infection.Euthanasing existing farm cats is not a useful approach as this often leads to the entry of a new population of cats, providing further kittens which will potentiate the infection and life cycle of disease
Vaccination – A live vaccine is available for the control of toxoplasmosis. The vaccine is administered ahead of tupping and is only conducted in replacement sheep. The only exception to this is if various groups are maintained separately on a farm where exposure levels to toxoplasmosis vary between groups. This can lead to variable levels of immunity and in that circumstance it may be advisable to vaccinate all sheep in non-exposed groups to avoid future losses, particularly if sheep move between groups where their exposure status could change.
Protozoa: Sporozoan
Neospora caninum
Body system affected- alimentary and reproductive
Life cycle: indirect – canids definitive host
Infective strategy – cattle ingest infected canid faeces
Diagnostic methods:
PM calf
Maternal antibodies
Treatment options: none, test and cull or don’t breed replacement heifers!
Causes over 10% of the UK abortion. Disease and the risk of abortion can be vertically transferred transplacentally from mother to daughter
Cattle ingest infected faeces
Transmission
Dogs are definitive hosts ofN caninumand are capable of shedding oocysts in feces after eating tissues of infected animals..Neosporaoocysts have an impervious shell that enables survival in soil and water for prolonged periods after canine feces have decomposed. Intermediate hosts such as cattle become infected by ingesting oocysts. Cattle do not produce oocysts and thus do not transmit infections horizontally to other cattle, but latent infection may endure permanently in their tissues and is transmitted to canids by carnivorism.
Clinical signs:
Abortion, between 3 and 9 months of pregnancy (particularly 5 to 7 months)
Still birth or premature calf
Occasionally, calves will have brain disease at birth
No other signs seen in the mother
Repeat abortions possible in the same cow
Diagnosis:
Clinical signs of little help
Characteristic heart and brain damage in aborted calf-pathologist to assist diagnosis
Identification of parasite in the calf tissue with immunohistochemical or PCR detection
Antibodies in the mother’s blood/milk 85%
Dogs are potentially a source of disease. So prevention must include:
a)Keeping cattle food and water away from dogs and foxes
b)High hygiene standards at calving. Dispose of placental membranes and aborted or dead calves before dogs can get them
However, transmission from mother to calf (known as vertical transmission) is far more important. Over 90% of calves born to mothers with antibodies toNeosporawill have been infected in the womb. The importance of transmission between cattle is less clear. Nevertheless, vertical transmission alone can maintain infection in a herd. To eliminateNeosporayou need to:
1)Identify infected cattle: All cattle with antibodies toNeosporaare sources of infection to their calves. Additionally cattle with antibodies are 20 times more likely to abort between 90 and 270 days of pregnancy than cattle without antibodies. Finally, on average, several studies have suggested that infected cows produce less milk than antibody negative cows.
2)Select only seronegative cattle for breeding.If you don;t cull seropositive cows, ensure that you only breed them to beef bulls. Heifers with antibodies should be sold for meat not bred.
These strategies look expensive to achieve, however the cost of neosporosis far outweighs the cost of eliminating it from the herd
Protozoa: Sporozoan
Babesia divergens
alimentary and reproductive
Life cycle: indirect via Ixodes ricinus
Pathogenesis- lyses red blood cells
Diagnosis:
Clinical signs
Recent movement to pastures known to harbour ticks
Blood smears can show up the parasite
Treatment options
Mild cases may recover without treatment.
Drugs available for treatment and prevention
Vaccines available abroad
Tick control
Babesia divergens.The disease is spread between cattle by ticks (Ixodes ricinusin the UK). The babesia is injected into the bloodstream by the tick and then invades the red blood cells and begins dividing, eventually rupturing the cell. Clinical signs begin around 2 weeks after infection
Clinical signs:
Increased temperature
Diarrhoea which ceases after around 36 hours and then becomes constipation
Red urine (due to haemoglobin produced by the rupture of the red blood cells) which becomes darker with time
Increased pulse rate
Abortion of pregnant cows
Death is rare in babesiosis in the UK
Diagnosis:
clinical signs
Recent movement to pastures known to harbour ticks
Blood smears can show up the parasite
Protozoa: Flagellates
Trichomonas fetus
Body system affected- reproductive
infertility caused by embryonic death
results in repeat breeding
pyometra, endometritis, or a mummified fetus
Life cycle-direct, found in the genital tractsof cattle
Infective strategy- males transferring it
Pathogenesis: The parasite interacts with bacteria that normally reside in the intestinal tract by adhering to the intestinal epithelium of the host
Diagnostic methods-
Focus on bulls: Repeated culture (single test identify 90%–95%), PCR isolation
Swab vaginal discharge/mucus
Treatment options-drugs, herd culling. Biosecurity, vaccines
When cows are bred naturally by an infected bull, 30%–90% become infected, suggesting that strain differences exist
Clinical signs:infertility caused by embryonic death. This results in repeat breeding, and attending stock persons often note cows in heat when they should be pregnant. Also see pyometra, endometritis, or a mummified fetus
Pathogenesis: The parasite interacts with bacteria that normally reside in the intestinal tract by adhering to the intestinal epithelium of the host
Diagnosis:Diagnostic efforts are directed at bulls, because they are the most likely carriers. Suction is applied to a pipette while it is used to vigorously scrape the epithelium in the preputial fornix. Alternatively, douching with saline or lactated Ringer’s solution (without preservatives) can be used. Aspirates or douches, concentrated by centrifugation, are examined using darkfield contrast microscopy. This material is also transferred immediately to the surface of a liquid culture medium such as Diamond medium
Vaccines developed some time ago for use in cows and evaluated in the field were not highly effective, especially in the absence of other control measures. However, the efficacy of whole-cellT foetusvaccines has recently been critically reviewed. Although there is some evidence to suggest that timely vaccination will improve reproductive performance in heifers, there is a distinct lack of evidence that vaccination will reduce “bull-associated outcomes.”
Protozoa: Ciliates Balantidium coli (pigs)
Body system affected- alimentary Life cycle-direct Pathogenesis-diarrhoea Diagnostic methods-FWEC Treatment options-drugs, improved hygiene Emerging issues-zoonosis Faeco oral transmission Significant human pathogen in developing countries
Faecal Smear
To demonstrate the presence of helminths and identify species or helminth groups present.To provide a quick and simple but relatively insensitive method for demonstrating helminth infection and identifying the eggs and larvae present.Equipment required.Fresh, moist faecesMicroscope slideCoverslipsSaline solutionMicroscopeMethod.Please ensure to wear gloves for this technique.1. Smear a small quantity of faeces on a clean microscope slide.
2. Mix with a few drops of physiological saline
3. Place a cover slip over the smear.
4. The faecal material should not be left in a lump in the centre of the coverslip but evenlyspread so that the microscope illumination can shine through.
Scan the faecal smear under the coverslip by starting at one corner and then moving the slide to the opposite corner.Move back overlapping the field and continue until the smear under the coverslip has been examine
Considerations.This method cannot be used for quantitative results.It only shows the presence of helminth eggs or larvae and enables the identification of species or groups present.The method is relatively insensitive and dependent on the number of eggsin the sample being high.It can be difficult to observe or identify the eggs as they may be partly or completely covered by debris.
Modified McMasters Technique for faecal worm egg count
Fresh, moist faecesMcMasters worm egg counting chamberMeasuring cylinder Saturated salt solution Pasteur pipette sBalance/weigh scales MicroscopeTwo glass beakers Pestle and mortar Straining device Centrifuge Spatula
1.Using balancing scales weigh out 3g of fresh, moist faeces into a beaker
2.Measure 42ml of saturated salt solution into the measuring cylinder and pour into the beaker
3.Mix the solution with a pestle and mortar
4.In order to remove large particles,pour the solution through a sieve or a fine mesh and collect the liquid into the second beaker(do not force particle through the sieve)
5.Discard the debris in the sieve
6.Using a Pasteur pipette mix the remaining liquidand pipette approximately2mls of solution, or enough solution to completely fill the two chambers on the McMasters slide.Method -Place the tip of the pipette in the gap between the base slide and the gridded coverslip and gently release the sample from the pipette, avoiding insertion of air bubbles and apply cover slip (where appropriate).
7.Leave thecounting chamber to stand for5minutes toallow eggs and to float to the top of the chamber.
8.Using the 10x objective examine the counting chamber under the microscope.9.Count all eggs seen over the grid, including those on and in the lines. Do not count any eggs outside of the grid.
10.Ensure that filled slides are read immediately after the 5minute wait period, as the saturated solution can damage the delicate worm egg structure.
ResultsMultiply number of eggs counted x 50 This calculation gives the number of eggs per gram of faeces providing a quantitative method of evaluating severity of worm burden, therefore, indicating the severity of the worm infestation.
Faecal Flotation.
The simple test tube flotation technique is a qualitative test for the detection of nematode and cestode eggs.This is a useful method to use in preliminary surveys to establish which parasite groups are present. Eggs are separated from faecal material and concentrated by a flotation fluid of an appropriate specific gravity.
1.Using balancing scales weigh 3g of fresh, moist faeces into a beaker.2.Measure 42ml of flotation fluidinto the measuring cylinder and pour into the beaker.3.Mix the solution with a spatula and break up faecal material.4.To remove large particles,pour the solution through a sieve and collect into the second beaker(do not force particles through the sieve).5.Fill a Falcontube with solutionto within 1 cm of the top.6.Place Falcon tube in rack to be collected by Lab Technician for centrifugation.7.Centrifuge for 5 mins at 1300rpm8.After centrifugationfill the Falcontube with flotation fluid to produce a small positive meniscus9.Cover the tube witha cover slipand allow to sit for 10 minutes.10.Place cover slip onto a microscope slide, taking care to avoid air bubbles.11.Examine under the microscope using x10to x40 objective lens.
Baermann Technique.
The Baermann technique is based on the active migration or movement of larvae.Faeces are suspended in waterfor 24 hours. The larvae move into the water and sink to the bottom to be collected for identification.EquipmentRequired.FunnelRubber tubing and clampCheesecloth strainerPasteur pipetteTest tubeMicroscope slideCover slipsMethod.Please ensure to wear gloves for this technique.As the preparation needs to be prepared 24 hours in advance, the equipment was set up yesterday and is now ready for you to collect a sample for assessment.1. Release the clamp on the rubber tubing allowing the liquid to pass into the beaker.2. Using a Pasteur pipette transfer a small amount of fluid to a microscope slide.3. Add one drop of iodine to fix the larvae and cover with a cover slip.3. Examine under a light microscope at low power (10x)for the presence of larvae.
Skin Scrapes.
Equipment required.Kiwi fruit Scalpel blade Liquid paraffinGlass microscope slidesWax marker crayonCover slipsPaper towel Method.1. Before taking a skin scrape, ensure you have all the equipment ready –in practice you would normally prepare several slides.
- Label your slide with the patient’s details and date.
- Place one drop of liquid paraffin in the centre of the microscope slide ready for the scraped material.(Liquid paraffin acts as a mounting medium which helps to make the detection and identification of ectoparasites easier.)
- Choose a few suitable sites on thekiwi fruit/animal for sampling.(In a live animal clip the hair from these areas to reduce the amount of hair on the slide.Areas immediately adjacent to papules, crusting or lesions tend to be good places to sample. If there is crusting or scaling try to avoid displacing it when clipping as these should be included in the sample.)
- Apply one drop of liquid paraffin to the skin surface (in this case, the kiwi fruit).
- Spread the liquid paraffin over the area using your finger.The liquid paraffin will help prevent the sample that is collected from dropping off the blade. (With a live patient, it is helpful to pinch the skin between your thumb and index finger and gently roll it prior to scraping.This will help to force deeply bedded parasites (Demodex mites) from the hair follicles, closer to the skin surface.)9. Hold the blade at a 45° angle to the skin surface, with the point slightly up and the majority of the flat part of the blade in contact with the skin –this allowsforcollection of plenty of skin debris. (This also helps protect the animal from any accidental cuts during collection of the skin scrape or if the animal moves.)10. Holding the kiwi fruit firmly on the table, scrape the surface by repeatedly moving the blade sideways and away from yourself (red arrows). (When working on a live patient either hold the skin taughtor continue to pinch it, in order to perform the scrape. The scraping movement should also follow the direction of the hair (if possible).Continue to scrape until there is a slight capillary ooze, beingcareful not to incise the skin-if there is a lot of blood in the sample it will be more difficult to examine.)
- The scraped material will now be visible on the edge of the blade.The material is transferred to the pre-prepared slide by tapping the blade in the drop of liquid paraffin. Alternatively, gently scrape the collected material off the blade using the edge of the glass slide. 1711. Once the sample is on the slide, place a coverslip over the area and gently press ontosample; ensure there are no air bubbles. Ensure there is enough liquid paraffin tocompletely cover the sample. The slide is now ready to be examined undera microscope.
Modified Knott’s Test.
The modified Knott’s method is used for the concentration and identification of microfilariae, specificallyrelated tothe heartworm Dirofilaria immitis.This is a simple test that can be performed easily and quickly in practice.Method.Please ensure to wear gloves and safety glasses for this technique.Due to the use of formalin in this method, steps 1 to 7must be carried out in the fume cupboard.1. Mix 1 ml blood with 9 ml of 2% formalin in a Falcon tube.2. Invert the tube gently 4 times to mix the solution.3. Place Falcon tube in rack to be collected by Lab Technician for centrifugation.4. Centrifuge at 500gfor 5 min.5. After centrifugation, discard supernatant.6. Stain sediment for 1-2 min with 1-2 drops of 0.1% methylene blue.7. Add a drop of the sample on a glass slide and cover with a coverslip.8. Examine under a light microscope at low power (10x) for microfilariae.
What is the main benefit to performing a faecal smear, rather than a McMasters test?
quick
no specilised slides
no solution to damage eggs
What is the main benefit to performing a McMasters Test compared to a faecal smear?
you can quantify the no. of eggs per gram of feces
What is the main benefit to performing a flotation test rather than a McMasters Test?
eggs are seperated from faecal material
centrifugal flotation techniques are considered more sensitive in recovering parasite ova.
when used in fecal floataion, what parasites can be identified using sodium chloride and what is its specific gravity
1.2 SG helminths and protozaon cysts and eggs preffered for gardia and lungworm larvae less sensitive for tapeworms not used for flukes, tapes and naeomotodes
when used in fecal floataion, what parasites can be identified using sodium nitrate and what is its specific gravity
1.2-1.33
good for commin helminths and protozoan cysta ns deggs
distorts gardia
not used for flukes and some unusual tapewom and nematode eggs
when used in fecal floataion, what parasites can be identified using sheathers and what is its specific gravity
1.25
Giardia cysts becoming distorted and difficult to identify for the novice, but a better overall ova yield than other solutions
less damaging
detects crypto
helminth and protozoan cysts and eggs
not good for flukes and some uncommon nematode and tape worm eggs
makes mess
when used in fecal floataion, what parasites can be identified using zinc sulfate and what is its specific gravity
1.18 good for common helminths and protozoan eggs and cysts preffered for gardia detects lungworm larvae not good for flukes, tapes and nematodes
when used in fecal floataion, what parasites can be identified using Magnesium Sulphate and what is its specific gravity
good for common helminths and protozoan eggs and cysts
distorts gardia
not good for flukes and some unusualtapes and naematode eggs
Which type of eggs are too large/heavy to float reliably in flotation fluid?
trematode eggs
. Which parasites that affect the veterinary species pass free larvae
nematodes
What are the main problems that can occur when performing a skin scrape on a canine patient?
exessive skin damage
cuts
Which companion animal ectoparasites would require a deep skin scrape to potentially identify?
Demodex canis and Demodex injai live in the hair follicle and Sarcoptes scabiei are burrowing mites, therefore deep skin scrapes are required to identify these parasites. Scraping the skin until capillary ooze is obtained is essential to ensure the epidermis (where the mites reside) has been removed.
Which companion animal ectoparasites would require a superficial skin scrape to potentially identify?
Cheyletiella is a surface-dwelling mite, so superficial skin scrapes should be performed. No capillary ooze is necessary. Superficial scrapings can also be used to diagnose ectopic Otodectes infestation, where mites are living outside the ear canals.
What is the primary host for Echinococcus granulosus?
Echinococcus granulosus, also called the hydatid worm, hyper tape-worm or dog tapeworm, is a cyclophyllid cestode that dwells in the small intestine of canids as an adult, but which has important intermediate hosts such as livestock and humans, where it causes cystic echinococcosis, also known as hydatid disease.
How can the zoonotic risk of Echinococcus granulosus be mitigated?
Echinococcosis is a zoonotic disease (transmitted from animals to humans) caused by the larval stage (hydatid cyst) of tapeworms. Eggs are excreted in the faeces of infected dogs and foxes and can be ingested by humans either by close contact with these animals or through contaminated food
Name FOUR diseases relevant to the veterinary species that can be carried by ticks
lyme
babesioisis
anaplasmosis
tick borne encephalitis
Which species of animal does Dermacentor variabilis affect?
Dermacentor variabilis is a 3-host tick, targeting smaller mammals as a larva and nymph and larger mammals as an adult. Although it is normally found on dogs, this tick will readily attack larger animals, such as cattle, horses, and even humans.
Name a Trichodectes louse that affects dogs.
Trichodectes canis is a chewing louse of dogs. It is very host-specific and cannot infest any other species than the dog. It can have serious effects in puppies and older, debilitated animals. T. canis can also act as an intermediate for the tapeworm Dipylidium caninum
Name a Trichodectes louse that affects cows.
Trichodectes scalaris
) Which Ctenocephalides flea affects dogs?
Ctenocephalides canis
Name TWO diseases that can be transmitted by Ctenocephalides species.
Ctenocephalides canis can act as intermediate hosts for parasitic worms including the double-pored tapeworm, Dipylidium caninum, and the nematode, Acanthocheilonema reconditum
Name TWO diseases that can be transmitted by Ctenocephalides species.
Ctenocephalides canis can act as intermediate hosts for parasitic worms including the double-pored tapeworm, Dipylidium caninum, and the nematode, Acanthocheilonema reconditum
Name a flea that affects hedgehogs.
Archaeopsylla erinacei
Name a flea that affects rabbits.
Spilopsyllus cuniculi
mites in Rabbits
Cheyletiella parasitovorax Listrophorus gibbus Psoroptes cuniculi Demodex cuniculi Sarcoptes scabiei var cuniculi Notoedres cati var cuniculi Trombicula autumnalis
Fipronil is toxic to
rabbits
Cheyletiella parasitovorax
Non Burrowing Mite
Life cycle 14-21 days
Females can live >10 days in the environment
Waisted mite with hooked palps and combed tips to legs
Visible with the naked eye ‘Walking Dandruff’
Transmission via infected rabbits and enviroonmental
Often carried subclinically
Clinical signs
Dorsal scaling, crusting
Variable pruritus
Partial alopecia
! Zoonotic potential
! Can infest other species
Diagnosis:
Microscopic examination of superficial skin scrape OR cellophane tape strip
Leporacarus (Listrophorus) gibbus
Non Burrowing Mite Brown, laterally compressed mite Usually non pathogenic Transmission via infected rabbits Clinical signs Moist, sebborhoeic dermatitis Variable pruritus Partial alopecia/abnormal moult ! Zoonotic potential ! Can infest other species Diagnosis: Microscopic examination of superficial skin scrape OR cellophane tape strip
Psoroptes cuniculi
Non Burrowing Mite
3 week life cycle
Can survive in the environment for >3 weeks
Visible with the naked eye
Oval shaped mites
Transmission via infected rabbits and fomites
One of most common causes of rabbit dermatoses
Clinical signs
Pruritic otitis externa
Thick pinnal crusts and ulceration
Neurological signs w/ otitis media/TM perforation
Rabbits may develop immunity
Environmental treatment
Diagnosis:
Otoscopic examination
Microscopic examination of superficial skin scrape or crusts
Sarcoptes scabiei var cuniculi
Uncommon
Highly pruritic, hyperkeratotic dermatosis
Yellow exudate
Face, feet, external genitalia
! Zoonotic
Superficial and deep skin scrapings
Microscopic examination of deep skin scrape
Demodex cuniculi
Rare Variable pruritus Can be non pathogenic Demodex: Microscopic examination of deep skin scrape or crusts Trombicula: Visible to naked eye
Trombicula (Neotrombicula) autumnalis (Harvest Mites)
Outdoor rabbits Late summer/early autumn Small orange mites Around ears, between toes Can transmit myxomatosis
ectoparasites other than mites in rabbits
Fleas Spilopsyllus cuniculi Ctenocephalides felis Lice Haemodipsus ventricosus Ticks Various esp Haemaphysalis leporis-palustris Myiasis
Fleas in Rabbits
Spilopsyllus cuniculi Rabbit flea Most commonly seen on wild rabbits Important vector for myxomatosis Ctenocephalides felis/canis Cat/Dog flea more commonly found on pets
Clinical signs: Pruritus, poor coat May be clinically normal Treatment of rabbit, in contacts and environment Observation of flea dirt Microscopic examination of whole fleas
Lice in Rabbits
Haemodipsus ventricosus Sucking louse Affects wild rabbits – rare in pets Clinical Signs: Pruritus, erythema, papules, alopecia, rarely anaemia May act as a vector for tularaemia
Diagnosis:
Microscopic visualisation of lice and eggs
Haemaphysalis leporis-palustris
Continental rabbit tick Affects wild rabbits – rare in pets C an be transmitted from other household pets Clinical Signs: Can cause anaemia in large numbers May act as a vector for myxomatosis, papillomatosis & tularaemia Diagnosis: Visible with naked eye Microscopic identification
Myiasis in Rabbits
Fly Strike – usually Lucilia spp. (Greenbottles)
Summer months
Usually primary but with underlying cause
Eggs can hatch within 12 hours to L1 (non pathogenic)
Within 3 days L1 L2 & L3 – cause tissue damage
Prevention (Cyromazine)
Larval Cuterebra spp can cause
subcutaneous infections
aberrant intracranial migration neurological signs
Diagnosis:
Visible with naked eye
Endoparasites in Rabbits
Nematodes Passalurus ambiguus Cestodes Taenia serialis Taenia pisiformis Echinococcus granulosus Cittotaenia spp Protozoa Eimeria spp Toxoplasma gondii Encephalitozoon cuniculi
Passalurus ambiguus
Oxyurid worm ‘pinworm’ Found in caecum and large intestine Adult worms measure 5-10mm Usually non pathogenic More common in wild rabbit populations Heavy infections may cause perianal pruritus in kits May have a role in caecal mixing Transmission between infected rabbits Direct life cycle Coprophagia spread and reinfection common
Obeliscoides cuniculi
Stomach worm - occasionally found in wild rabbits
Not reported in pet rabbits in UK
Trichostrongylus retortaeformis
Intestinal worm- Europe and Australia- not USA
Taenia serialis
Dog/Fox tapeworm
Larval stage Coenurus serialis
Form subcutaneous cysts (eye/tongue)
Taenia pisiformis
Dog/Fox tapeworm
Larval stage Cysticercus pisiformis
Abdominal cysts can cause discomfort and swelling
Eimeria spp
16 species of Eimeria which affect rabbits
Intestinal and Hepatic disease
Variable pathogenicity and predilection site
Young rabbits most susceptible
No cross immunity across species
Oocysts can persist for years in the environment
Not destroyed by common disinfectants or high temperatures
Intestinal Coccidiosis
Various including E. magna & E. irresidua
Clinical signs variable
Weight loss, abdominal distension, diarrhoea (+/- haemorrhagic), anorexia, depression
Hepatic coccidiosis
Eimeria steidae
Epithelial cells of bile ducts
Clinical signs include weight loss, ascites, jaundice, diarrhoea and hepatomegaly
Toxoplasma gondii
Intracellular coccidian parasite
Rabbit is intermediate host – cannot spread the parasite
Seen when grazing on pasture contaminated with cat faeces
Infection usually subclinical (19% seroprevalence)
Acute onset toxoplasmosis seen in young rabbits
Anorexia, lethargy, fever
Increased respiratory rate
Oculonasal discharge
Central nervous signs
Loss of foetuses if infected in pregnancy
Owner education re cat contamination of grazing
areas
Concurrent infection w Encephalitozoon commo
Encephalitozoon cuniculi
Obligate Intracellular protozoal parasite
Widespread in rabbit population (52% seroprevalence)
! Zoonotic
Potentially life-threatening infection in
immunocompromised humans
Infective spores shed in the urine
Remain viable in environment in extreme conditions
Infection via ingestion of spores or vertical transmission
Parasite primarily attacks CNS, kidney and eye
Clinical signs
Neurological
Head tilt, hindlimb weakness, paralysis, tremors, nystagmus, convulsions and urinary incontinence
Ocular
Cataracts and lens induced uveitis
Renal failure
Diagnosis challenging
Post mortem examination
IgM, IgG Serum antibody titres
Urine/CSF PCR
High prevalence makes prevention very difficult
Good hygiene practicesTreatment (Fenbendazole) not without risk
Ectoparasites in Guinea Pigs
Mites Trixacarus caviae Demodex caviae Chiridiscoides caviae Lice Gliricola porcelli Gyropus ovalis Trimenopon hispidum Fleas/Ticks Rare
Trixacarus caviae
Sarcoptid mite
10-14 day life cycle
Asymptomatic carriers common
Lesions usually dorsal neck and thorax but may
become generalised
Intense pruritus
Self trauma, secondary infection, seizures
Foetal resorption in pregnancy
! Zoonotic potential
Diagnosis:
Microscopic examination of deep skin scrape
Demodex caviae
Alopecia, erythema, papules, crusts
Head, forelimbs, trunk
Chiridiscoides caviae
Non burrowing fur mite
Usually found over dorsum
Only get clinical signs with heavy infestation
Alopecia, pruritus, self trauma
Cheyletiella parasitovorax
Scaling and pruritis along dorsum
Rabbits implicated
Gliricola porcelli &Gyropus ovalis
Common
Biting lice
Mild dermatitis
Heavy infestations can lead to alopecia and crusty lesions
Trimenopon hispidum
Rare biting louse
Eimeria caviae
Usually subclinical
Can cause diarrhoea
Young animals and breeding groups
Klossiella cobayae
Renal coccidian with few clinical consequences
Pelodera strongyloides
Nematode capable of invading mammalian skin
Pruritic dermatitis
Paraspidodera uncinate
Pinworm
Only clinical in severe infections
Rare. Most common in large collections
Ectoparasites in Rats
Radfordia ensifera
Rat fur mite
Ulcerative, crusty lesions over head and shoulders
Notoedres muris
Burrowing mite
Pruritic, warty papular lesions on extremities
Diagnosis by skin biopsy or clinical response to treatment
Various sarcoptid mites, Dermanyssidae
Polyplax spinulosa (sucking louse) rare
Fleas rare – usually from household contacts
Oxyurid Pinworms
Syphacia obvelata can cause perianal pruritus and tail base mutilation
Syphacia muris, Aspicularis tetrapterar not associated with clinical disease but can stunt growth
Diagnosis on tape strip microscopy S. obvelata or faecal flotation microscopy (banana shaped eggs)
Rodentolepis nana & Hymenolepis diminuta
Rat is definitive host
Disease only with heavy burdens
! Zoonotic potential
Giardia muris & Spironucleus muris
Eimeria
Pathogenic flagellates in rats
Myocoptes musculinus (A), Myobia musculi(B), Radfordia affinis(C)
Most common mouse fur mites
Life cycles from 8-23 days, direct contact
Common, often mixed infestations
Pruritus alopecia and ulceration
Classic patterns of distribution for different mites
Ulcerative, crusty lesions over head and shoulders
Notoedres muris
Burrowing mite – causes a parasitic otitis
Polyplax spinulosa
(sucking louse) rare
Fleas in mice
rare – usually from household contacts
Oxyurid Pinworms
in mice
Syphacia obvelata, Aspicularis tetraptera
As per rats
Heavy infections can lead to rectal prolapse
Rodentolepis nana & Hymenolepis diminuta
Rat is definitive host but can infect mice
Disease only with heavy burdens
! Zoonotic potential
Pathogenic flagellates Giardia muris & Spironucleus muris
Found in small intestine and caecum of mice
Can cause enteritis and diarrhoea in pups
Cryptosporidium parvum & C. muris
Colonise upper SI and stomach respectively
Mild pathogenicitiy malnutrition
Coccidia
Isospora and Eimeria spp (Eimeria furonis most severe)
ferrets
Generally subclinical except shelter and breeding groups
Gastrointestinal signs
Cryptosporidium spp.
in ferrets
Raw feeding a risk factor
Usually self limiting in healthy individuals
Signs of gastroenteritis
! Zoonotic potential
Giardia in ferrets
uncommon
Angiostryonglyus vasorum in ferrets
reported
Dirofilaria immitis in ferrets
not endemic in UK, uncommon in USA
Ectoparasites in Ferrets
Mites Sarcoptes scabei Otodectes cynotis Lynxacarus mustelae Demodex spp Ticks Fleas Ctenocephalides spp Pulex irritans Myiasis
Sarcoptes scabei in ferrets
Direct contact with other animals
Generalised alopecia and pruritus
Localised lesions of toes and feet
! Zoonotic potential
Otodectes cyanotis in ferrets
Ear mite (as per cats and dogs)
Can be asymptomatic
Severe crusting and pruritus secondary bacterial otitis
Lynxacarus mustelae (rare)
Fur mite
Ulcerative facial lesions in kits, immunosuppressed individuals
Demodex spp (rare) in ferrets
Secondary
Fleas in ferrets
Ctenocephalides felis, C. canis, Pulex irritans
Mild to intense pruritus – usually around neck
Flea bite hypersensitivity reported
Ticks in ferrets
Ixodes ricinus Common in hunting and stray ferrets Rare in pet ferrets Lyme disease not reported Can lead to anaemia in heavy burdens
Myiasis in ferrets
Uncommon
Ectoparasites in Birds
Lice Various Mallophaga spp – host specific Mites Dermanyssus spp Ornithonyssus spp Knemidocoptes (Cnemidoptes) mutans, K, pilae Sternostoma tracheacolum Various Feather mites – host specific Ticks Insects Hippoboscids Diptera Fleas – Rare Leeches
Lice in Birds
Most common avian ectoparasites Host species specific Often site specific Only Mallophaga spp (chewing lice) Amblycera & Ischnocera Complete life cycle on host Hippoboscids involved in transmission Heavy infestations can cause feather damage Important sign of debility/poor husbandry
Ticks in Birds
Hard Ticks (Ixodidae) in UK
Soft Ticks on imported birds
Summer/Early Autumn
Clinical signs can be severe even with low numbers
Irritation
Debility
Anaemia
Death
Tick borne diseases
Tick Reactions (usu Ixodes frontalis around head)
Extensive haemorrhagic swelling at tick site
Collapse
Emergency – aggressive treatment required
Environmental control
Mites in Birds
Dermanyssus spp (Red Mite)
Ornithonyssus sylvarium (Northern Fowl Mite)
Knemidocoptes (Cnemidoptes) mutans, K, pilae
Sternostoma tracheacolum
Various Feather mites – host specific
Dermanyssus spp - Red Mites
Dermanyssus gallinae Free‐living mite living in housing Breeds off the host Only feeds (blood) at night Can be challenging to diagnose Primarily poultry parasite but all species susceptibleHeavy numbers cause: Anaemia Debility Intense irritation Death in young/small birds ! Zoonotic potential Very Challenging to treat Easily seen with naked eye Often need to set environmental ‘traps’ Spots on eggs
Ornithonssus sylvarium – Northern Fowl Mite
Ornithonyssus sylvarium Poultry and aviary birds (also pigeons) Lives on host Most commonly found around vent, tail and breast Reddish brown colour More irritant than red mite Control easier as is obligate parasite Easily seen with naked eye on bird around vent Mites/eggs on faecal microscopy
Knemidocoptes (Cnemidocoptes) spp
Cnemidocoptes mutans, C. pilae
Long incubation period
10-14 day life cycle
More prevalent in spring/summer
Often asymptomatic carriers
Many species affected – poultry, budgerigars and passerines
Invade the follicle and stratum cornea:
Face and cere (C. pilae) – Scaly face in psittacines
Feet and legs (C. mutans) Scaly leg in poultry
Feet and legs (C. pilae, jamaicensis) Scaly leg in passerines
Feather shafts (C. gallinae) depluming itch in poultry
Sternostoma tracheacolum
Air sac mites
Infect trachea, syrinx, lungs and air sacs
Challenging to diagnose antemortem and treat
Mostly affects passerine birds
Clinical signs:
Respiratory tract signs
Coughing, gaping, head shaking, voice loss, excessive salivation, clicking, head bobbing
Signs exacerbated after activity
Increased mortality
Feather mites
Various species Host and site specific Spend whole life cycle on host Occasional feather damage Irritation in large numbers Diagnosis: Clinical examination, microscopy
Hippoboscids – Flatflies/Louseflies
Very common – especially in wild, debilitated birds Related to keds Blood sucking Main significance is vector effects Blood parasites Occasional anaemia in young birds Many different species Not host specific May be wingless or flighted Some complete lifecycle on hoost others may lay eggs in environment
Endoparasites in Birds
Protozoa Trichomonads Coccidia Giardia/ flagellates Nematodes Non pathogenic gizzard worms Capillaria Serratospiculum Syngamus trachea Haemoparasites
Trichomonads
in birds
Various species Psittacines (esp budgies) Raptors Passserines Columbiformes Poultry Yellow cases lesions in oropharynx, upper GI and respiratory tracts Usually spread by ingestion of infected prey/food items, direct contact, water or food bowls Motile flagellates Diagnosis: Examination of FRESH swab Metronidazole, ronidazole are prohibited in food producing species
Nematodes in birds
Various species of worm Not host species specific Range of sizes and body systems affected Some require intermediate host Risk of endotoxicosis from mass worm die off May be subclinical Diarrhoea, weight loss Ascaridia spp important group Serratospiculum (Air sac worm) Not seen in UK
Syngamus trachea (Gapeworm)
Distinctive Y shaped red worm, in permanent copulation
Earthworm is transport host
Psittacines, Raptors (owls) Corvids, less common in passerines
Affects respiratory tract
Gaping, coughing, dyspnoea, head shaking
Capillaria spp
Earthworm is intermediate host
Psittacines, raptors, occasionally passerines
Found in oesophagus, crop, intestines
Clinical signs
Oropharyngeal plaques, weight loss, regurgitation, diarrhoea
Haemoparasites
Various species Leukocytozoon Haemopooteus Plasmodium Most require ectoparasite vectors Ticks, flies, leeches Rare in captivity Can cause anaemia Malaria in Captive penguins & wild passerines Native wild bird reservoir
Ectoparasites of Reptiles
Mites are the most common Ophionyssus natricis (Snake Mite) Trombiculid mites (chiggers) NB may be involved in spread of disease Ticks – rare in captive bred reptiles Myiasis Leeches Lice – extremely rare
Ophionyssis natricis (Snake mite)
Affects all reptilian taxa
•Red, brown, black or grey mites
•7-16d life cycle
•Mites may be observed on the reptile or in the environment
•Eyes, ears, oral commissures, axillae, inguinal folds, cloaca
•Clinical signs
•Behaviour changes associated with irritation
•Hyperactivity, excessive bathing, rubbing
•Dysecdysis
•Secondary bacterial/fungal infections
•Dehydration, anaemia
•Can occasionally affect humans
•Quarantine, environmental and animal treatment
•Environmental persistence > 40 days
•Reptile & environmental treatment
Hirstiella trombidiiformis (Lizard mite)
Red or orange mites
Mites may be observed on the lizard or in the environment
Eyes, ears, oral commissures, axillae, inguinal folds, cloaca
Clinical signs and treatment similar to snake mites
Trombiculid mites (harvest mites)
May be seen on reptiles kept outdoors in autumn
Adults are free living and don’t cause disease
Larvae (Chiggers) can cause skin irritation
Hypoapsis Predatory mites NB Not a reptile parasite
Safe way to treat pathogenic mites
Ticks in reptiles
Common in free ranging or imported reptiles
Outdoor pets
Hard (Ixodes) & Soft bodied (Amblyomma)
Low numbers cause only mild skin irritation
Heavy infestations can anaemia
Transmission of other infectious diseases
Endoparasites of Reptiles
Protozoa Coccidia Cryptosporidium Flagellates Entamoeba Helminths Nematodes Cestodes Trematodes Haemoparasites Ivermectin even at low doses has led to flaccid paralysis and death in chelonians and crocodilians and must not be used in these groups
Coccidia in reptiles
Common finding
Agamids, Chameleons, Geckos most represented
Various spp with variable sporocyst numbers
Eimeria, Isospora, Sarcocystis, Caryospora spp
Direct life cycle – poor hygiene/overcrowding implicated
Clinical signs usually gastrointestinal
Sub clinical
Enteritis, anorexia, lethargy, weight loss, prolapse, death
Some spp can infect beyond GIT
Intranuclear coccidiosis in tortoises
Cryptosporidium in reptiles
Common cause of gastrointestinal disease
C. serpentes, C. saurophilum
Clinical Signs
Sporadic regurgitation of typically mucus covered prey (snakes)
Gastric mass may be palpable
Diarrhoea (lizards) with mucosal thickening of intestine
Weight loss, debilitation, death
Faeco-oral transmission
Can get subclinical shedders and non-ophidian reptiles can be carriers
Oocysts are very resistant in environment
Treatment not effective
No longer considered to be a significant zoonotic disease
Diagnosis:
Faecal, regurgitant, stomach wash microscopy
Repeat testing required due to intermittent shedding
Flagellates in reptiles
Common finding
Many can be commensals or of low pathogenicity
Trichomonads, Giardia, Hexamita spp
Intestinal disease
High numbers associated with anorexia, weight loss, diarrhoea
Hexamita parva (Tortoises) can cause fatal renal disease
Dessicate and die quickly
Diagnosis on fresh, warm samples
Diagnosis:
FRESH faecal microscopy
Renal biopsy for Hexamita
Repeat testing required due to intermittent shedding
WARNING:
Metronidazole has caused neurological problems in King and Indigo snakes
Entamoeba invadens
Commensal in herbivorous reptiles
Invade intestinal mucosa and cause disease in carnivorous reptiles (snakes)
High morbidity/mortality
Mixed collections major risk factor
Direct lifecycle – transmission through direct contqact with cyst form
Clinical signs:
Anorexia, weight loss, regurgitation, constipation, diarrhoea, neurological signs, death
Cestodes in reptiles
Found in all orders of reptiles
May be definitive, paratenic or intermediate host
Many spp non pathogenic
Complex life cycles and restricted range of hosts limits cases in captive reptiles
May see proglottids around cloaca
Ova in faeces
NB differentiate from tapeworm eggs of prey species
Trematodes (Flukes) in reptiles
Wild caught reptiles esp aquatic
Most require aquatic molluscs, fish or amphibians as intermediate host
Rare in captive reptiles
Generally non pathogenic
Spirorchiids pathogenic in turtles
Live in heart and blood vessels
Can cause ischaemia, necrosis and organ failure
Pentastomids (Tongue worms)
! Zoonotic potential Mostly imported reptiles as require intermediate host Actually primitive arthropods Migrate through viscera Can inhabit any tissue but commonly adults live in lungs Clinical signs may not be seen Respiratory problems, oral mucus Death in young animals with high burdens
Haemoparasites
in reptiles
Various species Hepatozoon Haemoprooteus Plasmodium Most require ectoparasite vectors Ticks, flies, leeches Rare in captivity Can cause anaemia
Recent trends in parasitic disease in the UK.
In 2020, a wet and mild winter and spring resulted in an influx of giardiosis which continued all the way into summer until we had a significant warm dry spell to stem the infection rates.
As we went into lockdown, more people were taking on puppies, although many pet owners were reluctant to visit their practice or register their puppies with a practice.
This had the result that no parasite prevention plan was set up for many puppies which had ramifications for all domestic parasites, but Angiostronglus vasorum (lungworm) was of particular note and an increase in angiostrongylosis was seen as a result.
A published study has shown a continuing lack of awareness by dog owners about A. vasorum and the risks it poses to their dogs, with only half of dog owners aware of lungworm and only 13% actually knowing what it is.
Examples of exotic parasitic disease
Dirofilaria immitis (Heartworm).
Babesia canis.
Dirofilaria immitis (Heartworm).
Filarial worms are nematodes infecting the connective tissues and vascular system of dogs and cats.
Mosquitoes, but also fleas and ticks, act as vectors for the different species.
Dirofilaria immitis, the canine and feline heartworm, is the most pathogenic species.
AlthoughD. immitisis not endemic in the UK, as mentioned previously, increasing numbers of infected rescue dogs are being imported from endemic countries.
Some of these animals have already been diagnosed with infection, with new owners in the UK being given varying accounts by rehoming charities regarding how serious infection may be, other new owners will be unaware that infection is present.
life cycle of Dirofilaria immitis
microfilariae are released by female worms into the blood stream where they become available to blood-sucking mosquitoes.
Microfilariae develop to the infective stage (L3) and are transmitted via saliva during feeding.
Larvae undertake an extensive migration within the canine host to reach the pulmonary arteries and the right heart and here they develop into the adult stages and mate.
In dogs, adult worms have a lifespan of up to seven years (although survival in cats is shorter), and microfilariae can survive between 2–18 months in the bloodstream.
Adult worms are found between subcutaneous and deep connective tissue layers in most parts of the body and adults can live for several years.
clinical signs of D. immitis
Infections with D. immitis may cause severe and potentially fatal disease in dogs and cats.
Despite its name, heartworm disease is essentially a pulmonary disease because the worms are predominantly located in the pulmonary arteries and the right heart is involved only in the later stages.
Clinical signs in the dog.
Clinical signs of the disease caused by Dirofilaria immitis develop gradually and may begin with a chronic cough which may be followed by moderate to severe dyspnoea, weakness and sometimes syncope after exercise or excitement.
Right side congestive heart failure develops later in the disease leading to ascites, oedema in the limbs, anorexia, weight loss and dehydration.
During the chronic stages of the disease, there may be a sudden onset of acute signs, for example, after severe spontaneous thromboembolism following the natural death of many heartworms, dogs may show acute life-threatening dyspnoea and haemoptysis.
“Caval Syndrome” - In small dogs, the displacement of adult worms from the pulmonary arteries to the right heart, due to pulmonary hypertension and a sudden decrease in right cardiac output, is a common event leading to “caval syndrome” which is usually fatal.
Most cats show no clinical signs of Dirofilaria immitis for a significant period after initial infection and many cats spontaneously self-cure.
Others may suddenly show a dramatic acute syndrome usually with respiratory signs such as coughing, dyspnoea and haemoptysis, with vomiting also frequently occuring.
Sudden death in apparently healthy cats is not an infrequent consequence of infection.
Feline heartworm disease is now recognised as a significant pulmonary syndrome defined as “Heartworm Associated Respiratory Disease” (HARD).
Clinical signs associated with HARD are anorexia, lethargy, weight loss, coughing, rapid heart rate, vomiting, diarrhoea, blindness, convulsions, collapse and sudden death.
diagnosis of D. immitis
A thorough clinical examination of imported animals, with D. immitis in mind, will identify clinical signs associated with the parasite.
Blood samples – may be examined for microfilaria in the dog after concentration by the Knott or the filtration test, although sensitivity is very low in cats.
Blood/serological tests for adult female antigens - commercial tests based on ELISA or immunochromatographic methods designed to detect these antigens are considered highly specific in both the dog and cat and some of them can be used in-house for a quick diagnosis.
In many cases, however, these tests yield false-negative results because of low worm burdens or the presence of only male or immature worms therefore, negative test does not rule out infection.
All imported dogs should be screened for heartworm.
Radiographs, electrocardiography and echocardiography – may be useful in determining the extent of pulmonary and cardiac pathological changes in dogs and cats.
treatment of d.immitis
Adulticidal therapy in dogs - melarsomine dihydrochloride is the only effective drug available for treating adult heartworm infections in dogs given by deep intramuscular injection in the lumbar muscles, the recommended follow-up treatment is administered 30–60 days later.
Surgical intervention is advised when multiple worms have been displaced into the right cardiac chambers producing sudden onset of “caval syndrome”.
Adulticidal therapy in cats - no registered adulticide drug for cats.
Decreasing doses of prednisolone are advised in cats in order to relieve respiratory distress with an initial dose.
Control strategies regarding parasites for travelling dogs and cats
Endemic areas to non-endemic areas travel - dogs should be examined for dirofilarial infections, treated against adult heartworms and cleared of microfilariae.
Furthermore, animals with unknown history should receive prophylactic treatment for two months to kill potential migrating L3–L4 and be tested for circulating antigens and microfilariae six and twelve months later.
Non-endemic area to endemic area travel – animals should be protected against adult filarial infections by receiving treatment within 30 days of arriving in the risk areas with macrocyclic lactone drugs.
For pets spending no more than one month in endemic areas, a single treatment, usually administered soon after returning home, is sufficient to assure complete protection.
In the case of longer visits, a monthly regimen should be administered with the first treatment being given within 30 days of entering the risk area and the last within one month of leaving
Public health considerations of d.imitis
Although heartworm can be past on to humans, the parasites generally do not develop to the adult stage.
In Europe, D. repens, not D. immitis, is the most important cause of human filarial infection.
Most human cases are asymptomatic and is probably underdiagnosed due to lack of awareness by physicians.
Babesia canis.
Babesia canisis a parasitethat infects red blood cells (rbc) leading to destruction of the rbcs and consequentally, potential anaemia.
Transmitted by several types of tick.
Found in many countries in Europe and is now becoming more relevant in the UK due to the movement of animals between countries.
The geographical distribution ofBabesiaspp. infections in Europe is highly variable and largely dependent on the distribution of the tick vector.
In central Europe, canine babesiosis appears to be one of the most frequently imported diseases and the endemic area of B. canis has expanded in recent years.
B. canis is considered to be endemic in northern Spain, Portugal, France, The Netherlands, Italy, and focally in central and eastern Europe up to the Baltic region with at least one endemic focus in the UK.
The vast majority of dogs diagnosed with babesiosis in the UK have travelled abroad or have been imported.
However, an outbreak of B. canis infection in untravelled dogs was reported in Essex, and B. canis-infected Dermacentor reticulatus ticks have been found in that specific area.
Cases of other Babesia infections in untravelled UK dogs have also occasionally been reported so the disease should remain a differential diagnosis for UK dogs displaying relevant clinical signs such as thrombocytopaenia, regenerative anaemia and pigmenturia even if they have not travelled
B. canis vector.
The two main tick vector species for babesiosis, Dermacentor reticulatus and Rhipicephalus sanguineus (brown dog tick) are present in the UK but are uncommon.
The UK had been previously considered free of babesiosis despite the presence of its vector, D. reticulatus.
However, the increase in animal movement across borders in recent years increased susceptibility to this pathogen establishing itself in the UK as was seen in four untravelled dogs in Harlow, Essex in 2016 and 2017.
There is also evidence that the second vector, the brown dog tick, historically unusual in Britain, is now surviving in localised environments and it is increasingly reported as being imported via travelling dogs.
Dogs rehomed from brown dog tick-endemic countries should be considered as a high-risk group for infestations and possible disease transmission.
It should also be noted that B. canis can be transferred by blood transfusion between dogs.
Life cycle of B.canis
Female ticks generally require a period of initial feeding of approximately 24–48 hours before Babesia sporozoites are available for transmission within their saliva to the dog.
Sporozoites infect erythrocytes, differentiate into merozoites and divide by binary fission eventually causing cell lysis.
In male ticks, transmission may be more rapid as they repeatedly feed taking only small amounts of blood, and they perform co-feeding with females and possibly feed from several different hosts.
cincla signs of B.canis
Babesiosis may be subclinical or may follow a peracute, acute or chronic course.
Acute disease - high fever, lethargy, anorexia, jaundice, vomiting and in some cases, red-coloured urine.
Chronic disease - moderate depression, intermittent fever, anaemia, myositis and arthritis.
Babesiosis in cats - lethargy, anorexia, weakness and diarrhoea.
Fever with icterus is uncommon, but signs may not be apparent until later stages of the disease.
Diagnosis of B.canis
Blood smears - a diagnosis of acute babesiosis can be confirmed with high sensitivity by the examination of thin blood smears to detect the parasite.
Serology - specific antibodies can only be detected from two weeks after the first infection and acute infections will therefore be missed if relying on serology for diagnosis.
Molecular diagnosis – species and subspecies-specific PCRs have been described and are being increasingly used in routine laboratory diagnosis.
The sensitivity of the PCR has been proven to be higher than blood smear examination especially for the diagnosis of chronically infected dogs, but false-negative results cannot be completely excluded.
treatment of B.canis
Chemotherapy should be initiated immediately after confirmation of a babesiosis diagnosis.
Imidocarb dipropionate, and in some countries phenamidine, are the drugs commonly used for the therapy of B. canis infection and in many cases, treatment with these drugs improves the clinical status, even though parasitological cure may not always be achieved.
There is little information on the therapy of babesiosis caused by small Babesia spp. in dogs and by Babesia spp. in cats, however, currently available chemotherapeutic agents used at the recommended dosage can reduce both the clinical severity and mortality rate.
Control strategies for travelling animals regarding B.canis
So far, no strategic control programmes have been developed for canine/feline babesiosis.
The risk of infection with Babesia spp. for individual dogs in endemic areas or for dogs travelling to, or through, such areas can be significantly reduced by effective tick control.
Chemoprophylaxis prevents disease but not infection and can be considered for all dogs entering an endemic area for short stays.
A vaccine, which can prevent severe disease, but not infection, is available in some European countries with which the level of immune-protection may vary depending on the species and subspecies of the strains.
The vaccination does carry risks of side-effects such as swelling and/or hard painful nodules at the site of injection and development of a stiff gait and reduced appetite for 2–3 days after vaccination.
Screening for exotic parasititc diseases.
ESCCAP UK & Ireland continue to recommend the following key steps in all imported dogs –
Checking for ticks and subsequent identification and treating for ticks if a tick treatment is not in place
Treating dogs with praziquantel within 30 days of return to the UK in addition to the compulsory treatment
Recognising clinical signs relevant to diseases in the countries visited or country of origin
Screening for Leishmania spp., heartworm and exotic tick-borne disease in imported dogs
A consistent approach of clinical examination and testing can help to recognise exotic infection early and appropriate monitoring or treatment implemented.
Endoparasite control in farm animals
- Consider seasonal risk and farm history of disease – utilising parasite forecasts
- Animal management.
- Pasture and grazing management.
- Use of parasiticides.
- Diagnostic and performance testing.
- Biosecurity, quarantine and biocontainment.
how can farm animal managment help reduce the risk of ectoparasites
Younger animals are, in general, more susceptible to parasitic diseases, particularly calves and lambs entering their first and potentially second grazing season and should be kept on safer pastures.
Grouping animals in tight age groups has benefits re. treatment and the usefulness of FEC in determining treatment requirements.
Grouping animals also helps with other management actions such as weaning and withdrawal periods post treatment.
Animals that have experienced repeated parasite infections should be kept on safer pastures and may be culled or not bred in favour of less susceptible animals.
Overstocking should be avoided - heavily stocked pastures create a higher infestation risk than lightly stocked pastures.
how can nutrition managment help reduce the risk of ectoparasites
Nutritional stress - it is well documented that animals under nutritional stress are less able to withstand a challenge from internal parasites.
Condition Scoring - using condition scoring to determine the need to treat animals can be a useful part of a parasite control strategy.
Undegradable Protein - ewes fed a ration that has high levels of undegradable protein will produce fewer worm eggs in their faeces around lambing.
Creep feeding lambs - provides additional nutritive support helping to delay early exposure to larvae on pasture.
Grazing on bioactive forages (contain metabolites that have beneficial effects on health) - such as chicory, birdsfoot trefoil and sainfoin has been shown to reduce the negative effects of parasitism in sheep.
It is not yet known whether bioactive forages act directly against incoming or established worms or whether they work indirectly by improving the nutritional status of parasitised animals.
how can pasture and grazing managment help reduce the risk of ectoparasites
Two key aspects to grazing management –
Nutrition - grazing management can provide high-quality nutrition, which will help animals withstand the effects of parasites and can also reduce the risk of acquiring worm infections.
Contamination - contaminated pastures are those that have been grazed by infected animals early in the year or in the previous season.
Safe pastures have not been previously grazed, such as newly reseeded fields and silage and hay aftermaths.
Multi-species (mixed) grazing - not all species share the same parasites so grazing different species on the same pasture, either at the same time or in succession, can help to break parasite life-cycles.
how can Use of anthelmintics.
managment help reduce the risk of ectoparasites
Anthelmintics are drugs that treat helminths (parasitic worms) including roundworm, tapeworm, lungworm and liver fluke.
Anthelmintics can be very effective and can target particular parasites or groups of parasites.
However, anthelmintics need to be used appropriately and the potentially negative aspects of their use, a key example being resistance, needs to be appreciated when designing treatment programmes.
Selecting an appropriate anthelmintic
Considerations –
Wide range of products available.
Wide range of preparations and methods of administration.
Many different chemical groups and activities.
What are the indications for use – when to use and how to use?
Withdrawal periods.
Resistance.
Environmental.
Principles of using anthelmintics
Choose the right product – knowing the parasite that is present and targeting treatment produces better results and reduces the likelihood of retreatment.
Source a narrow spectrum product where appropriate - reduces selection for resistance.
Administer anthelmintics effectively and handle and store them correctly.
Do not mix anthelmintics with any other product prior to administration.
Check the product has been effective by carrying out post-dosing FEC.
Benzimidazoles (BZ)
farm animals
- vary from drug to drug on their range of effect, e.g. albendazole is effective against roundworms, adult liver fluke and liver fluke eggs, whereas triclabendazole is effective against early immature liver fluke and adult liver fluke.
Levamisole (LV)
farm animals gastrointestinal and pulmonary nematodes, but has no activity against flukes and tapeworms and is not ovicidal.
Macrocyclic lactones (ML),
farm animals
including avermectins and milbemycins - active against many immature nematodes and arthropods.
Amino acetonitrile derivatives (AD)
farm animals
monepantel is effective against nematodes resistant to other anthelmintics.
Spiroindoles (SI)
farm animals
Derquantel used against roundworms in sheep.
how does Diagnostic and performance testing help prevent parasites in afarm animals
Diagnostic tests - such as Faecal Egg Counts (FEC) provide useful information when deciding the need for treatment, testing efficacy of a treatment and pasture management options.
Performance testing – for example, looking at daily liveweight gain, can also help provide a more targeted approach to worm control by identifying the worst affected animals.
Diagnostics and performance tests can identify issues before they become severe, can reduce the risk of anthelmintic resistance and improve dosing regimes.
how does Biosecurity, quarantine and biocontainment
help to prevent parasites in farm animals
Biosecurity- is the first line of defence and reduces/prevents the introduction of new diseases onto a farm from other farms.
Parasites can be introduced onto a farm by the introduction of diseased animals, contaminated feed, inappropriate faeces handling or by other species such as dogs and wildlife.
Biocontainment- reduces/prevents the movement/spread of infectious diseases once they have been identified on farm.
lice control in farm animals
Cattle - in cattle, a range of pour-on or spot-on synthetic pyrethroids, e.g. permethrin, are available for louse control, also pour-on and injectable macrocyclic lactones (MLs), e.g. ivermectin also commonly used.
Most insecticides registered for use on cattle are not active against louse eggs and so a second treatment may be required.
The timing and frequency of treatments depends on individual circumstances, however in many cases treatment in late autumn or early winter will give adequate control of cattle lice, often when cattle are housed for the winter.
Sheep - treatment of chewing lice in sheep is by organophosphate (OP) dip or by topical synthetic pyrethroids.
Pour-on products should be avoided in fully fleeced sheep, as this results in a less effective treatment and increases the risk of resistance.
mite control in farm animals
Cattle - only a relatively small number of products are authorised for use against mites in cattle.
Permethrin is the only pyrethroid in the UK used against chorioptic and sarcoptic mites in cattle.
Chorioptic mange - ivermectin, doramectin, eprinomectin and moxidectin applied topically as a pour-on are effective against chorioptic mange.
Sarcoptic mange – treatment with systemic macrocyclic lactones.
Psoroptic mange – extremely rare in cattle in the UK and difficult to treat – studies have shown doramectin (two treatments) and permethrin (off license) to be effective.
Sheep - as a result of resistance being demonstrated in Psoroptes ovis to the injectable macrocyclic lactones (ML) and concern that the use of these products is accelerating resistance to the MLs in gut-worm populations, there has been a recent move to more OP (diazinon) dipping for the treatment of sheep scab.
tick controll in farm animals
Cattle – topical application of pyrethroid starting before, and re-application throughout the challenge period is the standard preventative treatment.
As ticks spend most of their life-cycle in the environment, reduction in numbers can be achieved through pasture improvement, drainage and scrub clearance.
Sheep – cypermetherin and alphacypermethrin canbe effective to treat and prevent ticks in sheep.
Work continues at the Moredun Research Institute (MRI) to produce a new vaccine against the tick-borne disease louping Ill.
fly control in farm animals
Cattle - insecticide impregnated ear tags and tail bands containing pyrethroids, together with pyrethroid pour-on, spot-on and sprays, are widely used to reduce fly annoyance in cattle.
Sheep – blowfly populations are greatest during the summer months, although due to changes in climate the risk period can be from March to December in some areas.
Control methods in sheep include –
Shearing ewes prior to the onset of the high-risk period.
Control of parasitic gastroenteritis and removal of contaminated fleece around tail area.
Dipping or use of topical chemical formulations to prevent strike or inhibit larval growth.
Ensure all wounds and foot lesions are treated promptly.
Treatment of individual affected sheep involves physical removal of maggots, cleaning and disinfection of wounds and supportive treatment such as antibiotics, fluids and NSAIDs.
General methods of fly control
Various environmental control methods are available such as –
Screens and electrocution traps.
Aerosol sprays, residual insecticides applied to walls and ceilings and cards and incorporated in solid or liquid fly baits.
Improved farm hygiene, including appropriate disposal of carcases, will help to reduce breeding places for flies.
Praziquantel
companion animals tapeworms
Fenbendazole
companion animals
roundworms, Taenia spp. and Lungworm
Pyrantel embonate
companion animals
roundworm, hookworm
Milbemycin oxime
companion animals
roundworms, hookworms and heartworm
Moxidectin
companion animals
hookworms, roundworms, whipworms, heartworms
Environmental control of endoparasites
Parasitic contamination of the environment can occur in a number of ways, including the excretion of parasitic eggs or larvae in the faeces and the release of cestode proglottids.
The infection of intermediate or paratenic hosts, such as birds, rodents, slugs, snails or sheep is relevant for animals that hunt or scavenge.
Most environmental parasite stages are highly resistant to environmental degradation (from months to years).
Freshly excreted stages of many parasites can be directly infective, for example Taenia spp. and Echinococcus spp. eggs.
Other parasite eggs, for example Toxocara canis, require time to develop in the environment at appropriate temperatures to reach the infective stage.
It is therefore important to prevent initial parasite environmental contamination by implementing comprehensive parasite control programmes based on local epidemiological knowledge.
Parasitised animals should be treated to minimise environmental contamination.
As it is difficult to control where outdoor cats defecate, particular attention should be given to worm control in cats.
Where possible, eliminate access to intermediate and paratenic hosts.
The safe disposal of animal faeces is vital and measures to facilitate faecal removal, such as the provision of disposal bins and bags should be encouraged.
Because eggs may persist in the soil for months or years for very contaminated areas, such as highly populated kennels, extreme measures may be needed for decontamination, including the removal of sand/soil or covering the soil with concrete or asphalt.
In kennels or multi-animal households, the strict treatment and quarantine of new entrants is essential to avoid the introduction of infected animals.
Allowing exposure to sunlight and drying of contaminated areas can assist in reducing the level of contamination.
Fipronil
fleas, lice, ticks
Imidacloprid
flea
Permethrin
fleas, ticks
Selamectin
fleas, ear mites, Sarcoptes scabiei
Afoxolaner
– fleas and ticks
describe the GIT of rabbits
Dentition Elodont incisors and cheek teeth Incisors modified to form chisel like shape Enamel deposited Diet Strict herbivoresCaecotrophy/coprophagy Gastrointestinal anatomy and physiology Hindgut fermenters Hindgut fermenter Simple stomach Large caecum and colon
describe the dentition of rabbits
Hypsodont arradicular
Dental formulae
2 0 3 3 / 1 0 2 3
describe the dentition of guinea pigs
1 0 1 3 / 1 0 1 3
Enteric nervous system
myenteric plexus informs movement
submucosal plexus informs secretions
Average weight of rabbits
1000-8000 g
Verage body temp of rabbits
38.3
resperatory rate of rabbits
35-60 bpm
pulse rate of rabbits
220 bpm
describe the muscoloskeletal system of rabbits
Light flexible skeleton
6-8% bodyweight (For comparison Cat skeleton 13-14% bodyweight)
Relatively large musculature
Muscle mass comprises 50%
Body conformation very variable with breed
Lifestyle leaves them prone to osteoporosis and fractures
Hindlimbs carry more muscle mass than forelimbs
Reflect need to evade predators through fast acceleration and high speed locomotion
Capable of violent kick
Secure handling essential
Vertebral fracture (L7) from kicking
Naturally curved spine
Flattened ribs
Spine C7, T12-13 L6-7 S4 Cd 16
(usually 12 T and 7 L)
Spinal cord extends into sacral vertebrae
In most other species ends within caudal lumbar region
12 paired Ribs
7 true ribs
5 false
Radius and ulna completely fused
Tibia and fibula partially fused
Fibula runs over only half od the tibia
At rest entire plantar aspect of hindlimb rests on ground – toes to hock
Digitigrade when running
Forelimb feet have 5 digits
Hindlimb feet have 4 digits
All extend into a long curved claw
Rabbit – Pectoral girdle
Pectoral Girdle Paired clavicles Slender scapula Hooked suprahamate process of acromion Sharply triangular infraspinous fossa Articulates with humerus Sternoclavicular ligament is only direct attachment to axial skeleton Other major attachments via musculature
Rabbit – Forelimb
Typical mammalian forelimb Humerus Articulates with scapula proximally Radius and ulna Completely fused in older animals Deeply bowed Two rows of carpal bones Distal row articulate with metacarpals Five metacarpals Forelimb feet have 5 digits D1 – 2 phalanges D2-5 – 3 phalanges
Rabbit – Pelvic Girdle
Pelvic Girdle is elongated with an oval obturator foramen
Ilium
Ischium
Pubis
Acetabulum formed from ilium, ischium and os acetabuli
In other species, pubis included in acetabulum
Rabbit – Hindlimb
Femur Ventrodorsally flattened Articulates only with the tibia Tibia and Fibula Fused distally Tarsus 6 Tarsal bones in 3 rows Prominent calcaneus Distal row articulate with metacarpals Five metatarsals (MT1 very small) Hindlimb feet have 4 digits All digits have 3 phalanges
describe the skeleton of guinea pigs
Similar vertebral structure to myomorph rodents
Reduced coccygeal vertebra (4-6) as no tail
Vertebral column (32-36)
C7, T13-14, L6, S2-3, Cd 4-6
13-14 ribs
1-6 true ribs – articulate with sternum
7-9 False ribs (articulate with 6th rib cartilage)
10-14 Floating ribs
Pectoral Girdle
Clavicles are present between scapulae and manubrium
Large flat scapula & rod like clavicle
Forelimbs
Long limbs compared to other rodents
Ulna and radius separate – unable to rotate carpus
7 carpal bones in 2 rows
Manus - 4 Metacarpals and 4 digits,
3 phalanges on each digit
Distal phalanx is arched
Shorter nails cf Hindfeet
Guinea Pig – Pelvic Girdle
Pelvic Girdle = Ilium, Ischium, Pubis
Pubic symphysis mineralises & fuses within first year
Pelvis of female joined at pubis & ischium by fibrocartilaginous suture line
Relaxin production in pregnancy softens the symphysis
Separation of pelvis (7-8mm)prior to parturition
Must breed at < 6 months
Os penis c. 10mm length, full length of glans
Guinea Pig – Hindlimbs
Typical Mammalian Femur Hystricomorphs have a separate fibula and tibia Tarsus 6 bones in 2 rows Pes 3 Metatarsals and 3 digits 3 phalanges on each digit Nails longer on Hind feet
Musculoskeletal system – Chinchilla
Axial Skeleton
Fragile skeleton
Vertebrae C7, T13, L6, S2, Ca23 (51 vertebrae)
13 pairs of ribs.
Appendicular Skeleton
Especially long femurs and tibias for jumping
Separate Tibia and Fibula (as per all Hystricomorphs)
Manus and pes both have 4 digits (unlike G pig)
Chinchilla- Dentition
Monophyodont, heterodont dentition ALL TEETH are: Open rooted (Arradicular) Continually growing (Hyspodont) Dental Formula (20 teeth) I 1/1 C0/0 PM 1/1 M 3/3 Diastema Cheek teeth (molars and premolars) Yellow enamel coated incisors (Iron) 12mm growth/weekUpper incisor growth > Lower incisors
Musculoskeletal Anatomy Degu
No systematic assessment of degu anatomy & physiology
Key Features:
Vertebrae C7, T13-14, S 2-3
5 digits FL & HL
4 well developed clawed digits forelimb and hindlimbs plus smaller D5
On FL D5 has nail instead of claw
Bristles extend over toes on HF
Prominent auditory bullae
Proximal ends of tibia and fibulaa fused
Usual hystricomorphous musculoskeletal anatomy
Dentition - Degu
Monophyodont, heterodont dentition ALL TEETH are: Open rooted (Arradicular) Continually growing (Hyspodont) Occlusal surface of cheek teeth have figure of 8 appearance (hence genus name Octodon) Dental Formula (20 teeth) I 1/1 C0/0 PM 1/1 M 3/3 Diastema Orange enamel coated incisors (Iron) NB Ocular signs in degus usually dental
Overview of Rabbit Reproduction
Male – Buck Female – Doe Juvenile – Kit (Kitten) Sexual maturity variable Small breeds 4-5 months Medium breeds 4-6 months Large breeds 9-12 months Gestation period = 30-33 d Litter 4-12 Altricial kits induced ovulators Long Day Breeders Breeding season Jan-Oct in wild Domestic rabbits can breed year round Induced/Reflex ovulator Sexual receptivity variable No defined Oestrus cycle Oestrus period up to 14 days followed by 2-4 days of non-receptivity Ovulation within 10-13 hours of mating Pregnancy in 75% matings Can have pseudopregnancies if mounted by other female or infertile male – last 18 days
breifly describe induced ovulators
genitle somatosensory stimuli+ GnRH release+ LH surge
breifly describe spontanous ovulators
ovarian steriod hormones produced by maturing follicles= pulsate GnRH relaese= Pre-ovulatory LH surge
Gender Determination
rabbits
Apply gentle pressure on the genital orifice to evert the penis or vulva
Males (Buck) Penis - cylindrical organ with a oval-shaped urethral opening. Two hairless scrotal sacs cranially. Females (Doe) Vulva - leaf-like appearance with a slit-like opening. Females of some breeds may have a large dewlap Sexually mature does Occasionally in males Males have fewer teats Sometimes no teats Behaviour Females more territorial Females burrow Male Scent marking
Male Rabbit (Buck) Reproductive Anatomy
Rounded penile sheath and urethra – more easily extruded from 2 months of age Two testes descend at 10 -12 weeks of age Hairless scrotal sacs Large epididymal fat pads Lie cranial to the penis Spermatogenesis from 7-8 weeks No sperm in ejaculate until about 4 months 0.3-0.6ml ejaculate 150 to 500 × 106spermatozoa per ml Inguinal canal remains open throughout life Able to retract testes into abdomen Cremaster muscle Outside Breeding Season Fear Famine Disputes No os penis No glans penis Accessory sex glands Vesicular gland Proprostate gland Paraprostate Bulbourethral glands Prostate gland Bilobed except paired bulbourethral glands May have rudimentary nipples Inguinal Glands White Brown
Female Rabbit (Doe) Reproductive Anatomy
Duplex uterus: 2 elongated ovaries 2 uterine horns 2 cervices – enter vagina separately 1 vagina – large and flaccid Rabbit does NOT have a uterine body. Mesometrium – fat deposition Urethra enters vagina at urogenital sinus Bulbourethral gland lies on dorsal wall of vestibule Ovaries are more elongated and located more caudally than in the bitch Suspensory ligaments relatively long Fatty broad ligaments Large blood vessel compared to the bitch Friable
rabbit breeding considerations
Does should be bred before 12 months of age
Reduced conception rate and smaller litters after this
Can lead to dystocia
Breeders may plan to coincide with show season
Breeding life
Doe up to 3 years
Buck is around 5–6 years
rabbit mating behaviour
Signs doe is ready to mate:
Digging, scenting, increased aggression, increased activity, chin rubbing
Territorial – take doe to buck (doe aggression)
Buck will follow doe, may urine spray her
Receptive doe:
Hopping in circles, may flatten to the floor, chin rubbing, lordosis, mounting, swollen & pink-purple vulva
Act of Mating
Buck grabs doe by neck with teeth
Mounts her, thrusts vigorously
Relatively quick ejaculation
Doe runs away or bites/kicks buck
Semen is deposited into the anterior vagina
sperm individually pass through the cervical mucus
Act of mating stimulates ovulation
Repeated matings increase conception likelihoo
rabbit pregnancy
Detection From Day 6-7 ultrasonographically From day 11 radiographically Palpable by day 12-14 (marbles) Gestation 30-33 days (average 31) NB Pseudopregnancy only 16-17 days Nest building Fur plucking - dewlap, flanks and belly to expose the nipples Using hair to line the nest Burrowing/Digging Placenta Hemochorial maternal-foetal interface- maternal blood comes into contact with fetal blood
rabbit partuition
Should be left alone as due date approaches
Decreased appetite and nest building 2-3 days
Familiar environment
Suitable for doe and kits for 8 weeks
Kindling
Parturition – 30 mins – a few hours
Usually eat the placentas
Don’t disturb for a few days
Dwarf breeds more prone to dystocia
Select from lines with good litter sizes
Giant breed breeders often select for small litters
describe rabbt kits
Kits are altricial (hairless with eyes closed)
Maternal transfer of immunity occurs before birth
Weigh 50-60g (breed variable)
Kits don’t leave nest for at least 2-3 weeks
Fur from 7 days – thick by 12 days
Eyes open 10-12 days
Do not handle unnecessarily!
describe rabbit lactation
Variable number teats/mammary glands Usually 4 pairs of mammary glands 1 x Thoracic pair 2 x abdominal pair 1 x inguinal pair 6-7 Ductal systems per gland Terminal duct lobular unit structure 30-40% mammary growth and development during gestation - Remainder during lactation Kits have total dependence on milk until day 10 Will suckle 1-2 times daily for 3-5 minutes Milk high in fat and protein Bucks can have a pair of teats
describe rabbit weaning
Start to show interest in solid food 2-3 weeks
Caecotrophy starts 3 weeks
Very careful timing to ensure bacteria not harmful
Can safely get to caecum for colonisation
Weaning 4-6 weeks
Establish on hay before introducing pellets gradually
Adult Rabbit stomach pH 1-2
Rabbit kit pH6
Milk oil is a protective, antibacterial substance
Hand rearing last resort only
Rabbit milk replacer
Need high fat content
Probiotics
describe spaying rabbits
Neutering recommended for all non breeding does > 6 months
Uterine adenocarcinoma – 50-80% intact Does >3yrs old – metastatic.
Midline approach
Very thin rectus abdominis
Prone to adhesions – careful tissue handling
Fat around ovaries and in mesometrium
Two uterine horns, two cervices, ligate cranial vagina
Synthetic monofilament suture material as prone to reactions
rabbit castration
Prescrotal or scrotal approach
Open inguinal ring
Must close tunic to prevent herniation
Can be fertile up to 6 weeks post neutering
how long is the oestrus cycle in mice
4-5 days
how long is the oestrus cycle in
16 days
how long is the oestrus cycle in guinea pigs
15-17 days
how long is the oestrus cycle in degus
21 days
how long is the oestrus cycle in chinchillas
30-50 days
describe ovulation in mice
non seasonal
polyoestrus
spontanious
describe ovulation in rabbits
partly seasonal
induced
describe ovulation in guinea pigs
seasonal
polyoestrus
spontanious
describe ovulation in degus
induced or spontanious
describe ovulation in chinchillas
poly sesonal
how long is gestation in mice
19-21 days
how long is gestation in rabbits
31-33 dyas
how long is gestation in guinea pigs
59-72 days
how long is gestation in degus
87-93 days
how long is gestation in chinchillas
111 days
how many young per litter do mice have
5-12
how many young per litter do guinea pigs have
1-6
how many young per litter do degus have
3-11
how many young per litter do chinchillas have
2
age of sexual maturity in mice
6-8 weeks
age of sexual maturity in rabbits
4-6 months
age of sexual maturity in guinea pigs
4-6 weeks
age of sexual maturity in degus
10-11 months
age of sexual maturity in chinchillas
8 months
gender determination in rodents
Challenging and stressful for rodents
Genitoanal distance most reliable method
Up to twice distance in males
Identification of penis/testes
Open inguinal canal and testes retraction
Presence/Absence of nipples
Male Guinea Pigs and Chinchillas can have nipples
Females and males have a prominent urinary papillae (cone)
Clitoral and penile morphology alike
Male Hystricomorph genitles
In most rodents the testes are large (cf body size) and descend into the scrotal sac following puberty No true scrotum – parascrotal sac Guinea Pig – Prescrotal sac, inguinal or abdominal Chinchilla – often inguinal Degu – Abdominal or Inguinal Accessory sex glands Seminal vesicles Prostate Coagulating gland Bulbourethral gland Preputial gland Penis Os penis Spiculated Glans penis
Female Hystricomorph genitles
Bicornuate uterus Vaginal closure membrane Resolves during oestrus and parturition Long oestrus cycles G. Pig 15-17 Chinchilla 30-42 Degu 17-25 Precocial Young Long gestation periods G. Pig 59-72 Chinchilla 105 – 120 Degu 90
Reproductive cytology in rodents
Cytology of vaginal secretions can be used to determine stage of oestrus cycle in rodents
4 distinct periods
Proestrus
Oestrus
Metoestrus
Dioestrus
Method
Flush vagina with 100µl of distilled water
Air dry slide
Stain (crystal violet/meth blue/diff quick)
Count lymphocytes
Count epithelial cells – do they have nuclei?
Copulatory Plug
rodents
Copulatory plug formed by coagulated ejaculate and sloughed vaginal epithelium
Solid waxy mass
Can identify post copulation as confirmation
Possible functions
Sperm storage, leakage prevention, induce pseudopregnancy, prevent later fertilisation by other males
Remains in place for 8-12 hours
Often found on cage floor rather than in vagina
Thought to seal vagina and make it more likely for mating to be successful
Male Guinea Pig (Boar) Reproductive Anatomy
Reach puberty at 2.5-3 months of age
Boars (and sows) have single pair of inguinal mammae/teats
Large paired tests
Prescrotal sac
On either side of perineum in shallow scrotal sacs
Fat pads
Fully descended by 3-4 month
Inguinal canals remain open for life
S shaped penis – body & glans (unlike rabbit)
Glans penis has rounded tip covered with saw-toothed
white scales or spurs
Os penis – entire length of glans ( ~ 10mm)
Intromittent sac (unique to hystricomorph rodents)
Invaginated portion of glans everted during sexual activity
Accessory sex glands
Smooth seminal vesicles – often mistaken for uterine horns
Accessory sex glands
Smooth seminal vesicles – often mistaken for uterine horns
Coagulating Glands
Bulbourethral glands
Paired
Prostate
Bilobed
Rudimentary preputial gland also may be present
Androgen dependent sebaceous glands
Peripenile sebaceous glands
Often become impacted
Female Guinea Pig (Sow) Reproductive Anatomy
Puberty 2-4 months
Seasonally Polyoestrus
Oestrus 8-11 hours
Spontaneous ovulation
Hemochorial placenta
Gestation 59-72 days (average 68)
Shorter in primiparous sows and smaller litters
Can palpate fetuses from 15 days gestation
Unique GnRH different to regular mammalian GnRH
Pseudopregnancy rare (17 d)
Bicornuate uterus with short uterine body and single cervix
No vestibule between vagina and external vaginal orifice
Paired intraperitoneal ovaries
Cystic Ovarian disease common in sows
Dystocia common (remember fusion of pubic symphysis)
Must be mated before 6 months of age
Guinea Pig Neonates and Lactation
Birthing brief 15-40 minutes Male should be removed Will attempt immediate re mating 2-4 pups in litter (1013) 40-115g at birth inversely proportional to litter size Single pair of inguinal teats Milk High in fat, protein, lactose Vitamin C Kitten milks suitable Weaned 21 days May eat hay, pellets, veg from birth Separate male and female pups at weaning
Male Chinchilla (Boar) Reproductive Anatomy
Puberty 8-9 months Lack a true scrotum Testes often inguinal Seasonal variation in testis size (smaller in summer) Accessory sex glands Vesicular Glands (long and tubular) Prostate Gland (Paired large ventral lobes & small dorsal lobes). Bulbourethral Glands Penis Sigmoid flexure Spurs on glans Os penis in distal portion Intromittent Sac Spermatogenesis occurs at about 2-3 months. Copulatory maturity is not until about 8 months – later than other spp. Breeds all year round Copulatory plugat mating.
Female Chinchilla (Sow) Reproductive Anatomy
Puberty 4-6months Large urethral process cranial to vagina Closed vaginal orifice Often mistaken for males Duplex Uterus Two cervices Unlike other hystricomorphs which have one cervix Seasonally polyoestrus (Nov – May in Northern hemisphere) Oestrus cycle 30-42 days Oestrus last 12-48 hours Characterised by open vulva and mucoid discharge Waxy plugs expelled at start of oestrus (cf copulatory plugs) Post partum oestrus 12 hours after birth Can breed in monogamous pairs or harems 1 male : 2-6 females Gestation period 111 days (105-120) Hemoendothelial placenta Dystocia rare Fully precocial young Litter size 1-6 (Average 2 kts) 30-50g at birth Three pairs of mammary glands 2 x lateral thoracic 1 x inguinal Weaned 6-8 weeks Handrearing similar to other caviomorphs
Male Degu Reproductive Anatomy
Males greater anogenital distance cf females
Internal testes
Abdominal or Inguinal
Degus have lower body temperature than other rodents
No true scrotum
S shaped penis
Spiculated glans penis
Two openings
Dorsal urinary meatus, Ventral intromittent sac
Os penis – cranial to perianal circle
Accessory Sex glands
Prostate - 3 pairs of lobes
Vas deferens and seminal vesicles open independently into urethra
Males sexually active only June – July in wild
Pet degus can breed year round
Can get fur rings like Chinchillas
Female Degu Reproductive Anatomy
Males greater anogenital distance cf females
Slowest maturing hystricomorph rodent
3-21 months (usu. 6-8 months)
Previously thought to be induced ovulators
Female only groups will spontaneously ovulate
3 week oestrus cycle
Bicornuate Uterus
Vaginal opening immediately behind urinary papilla (cone)
Gestation 90 days
Usually max 2 litters per year
Don’t have a post partum oestrus until pups weaned
Males sexually active only June – July in wild
Pet degus can breed year round
Degu Neonates and Lactation
Litters of 3-11 (average 5/6 pups)
8-17g at birth
Least precocial of the hystricomorphs
Eyes open 1-3 days old
Four pairs of nipples
3 x pairs lateral between front and hind limbs
1 x pair caudal ventrum to enable suckling when female vigilant
Wean 4-6 weeks
Chewing practice from 6 days – don’t digest until 2 weeks old
Coprophagy from day 3 to help colonise intestines
Rabbit Kidney
Unipapillate kidney – similar to rodents
One papilla, one calyx enter ureter directly
Renal pelvis is a direct extension of renal pelvis
Simple medullary structure
200,000 nephrons in adult kidney
Number of glomeruli increase after birth
Right kidney cranial to left kidney
Surrounded my thick adipose tissue
Environmental adaption over generations
Long medullary region in arid regions
Short medullary region in lush environment
Rabbit Lower Urinary Tract
Ureters drain into bladder in does In bucks, lower down on neck of bladder Tough, thin walled bladder Can rupture if over distended Urethra opens into vagina in does Penile urethra in bucks Alkaline urine (pH 8.2) 130ml/kg/day – very variable Urinary excretion of Calcium Varies in colour Urochromes Red, orange, brown, yellow Porphyrinuria Can see true haematuria Pseudohaematuria Excessive, prolonged dietary calcium intake urolithiasis
Calcium Metabolism in rabbits
Passive absorption from gut
Increased set point for Ca stimulated PTH release
High serum Ca
Not maintained within narrow range
Dependent on dietary intake, not vitamin D
Excess excreted via kidneys
Renal fractional excretion 45-60% c/f <2% in other mammals
Hypercalciuria in rabbits
Alkaline urine promotes Calcium precipitations Excess calcium in diet leads to urinary sludging Risk Factors Pelleted diets fed to excess Alfalfa, watercress, kale, dark leafy greens high in Ca Reduced mobility Reduced water intake Neutering Urinary tract infection Requires flushing Husbandry review Can progress to urolithiasis Usually Calcium carbonate Surgical Removal
Hystricomorph urinary overview
Adapted to semi arid environment Variable water conservation Thick medulla cf cortex Long loops of henle Good concentrating ability Can survive long periods without water in the wil Prone to complications if dehydration in captivity Urethra can be catheterised Herbivores Alkaline urine Calcium metabolism & excretion
Guinea Pig Urinary Anatomy
Kidneys sit between T12 and L3 and T13 and L4 (L) Right kidney cranial Unipapillate kidneys Large renal pelvis Pyriform urinary bladder Lies entirely within pelvis when empty Extends beyond pubis when full No trigone Urethra Opens outside vestibulum so can be catheterised Urine Alkaline Urine (pH 8.5) Thick with sediment Normal urine contains crystals Calcium oxalate, Calcium Carbonate, Ammonium phosphate May see porphyrinuria as in rabbits Older females prone to urolithiasis
Urolithiasis in guinea pigs
Older Guinea Pigs Males and Females Usually Calcium Carbonate Can see Calcium oxalate and Struvite Risk Factors High Calcium diets facilitate hypercalciuria Inadequate water intake Excess Vitamin C Can interfere with urinary glucose levels Has high oxalate levels
Chinchilla Urinary Anatomy
Thick renal cortex cf medulla
Long loops of henle
Similar to desert rodents
Efficient concentrating ability
Often have USG > 1.045
Can concentrate up to 4,000 mOsmol/kg
Elongated renal papillae
Ureters empty into urinary bladder near to neck
Urethra
Opens outside vestibulum so can be catheterised
Urine
Alkaline Urine (pH 8.5)
Eliminate excess cacium ~ 80% through faeces
Only 1-3% renal excretion in urine
Still have variable urine calcium concentration
Urolithiasis is reported (mostly Ca Carbonate)
Degu Urinary Anatomy & Physiology
Thick renal cortex cf medulla Long loops of henle Similar to desert rodents Efficient concentrating ability Can concentrate up to 4,000 mOsmol/kg Significant seasonal variation Also condense water in nasal passages to prevent exhalation of moisture! Urine Produce more urine at night cf daytime Reflects UV and up to 40% of incident light Visual territorial scent mark Can see porphyrinuria
Adrenal Glands - Rabbits
2 ovoid to round adrenal glands at cranial pole of the kidney
Remarkable variation in adrenal artery numbers (3-18)
Regulate stress response
Cortisol is predominant stress hormone
Zona fasciculata
Production of steroid androgen hormones
Zona reticularis
Aldosterone
Zona Glomerulosa
Spontaneous hyperplasia/neoplasia described
Endocrine Pancreas - Rabbit
Diffuse gland situated along stomach, duodenum, liver Insulin production Beta cells of islets of Langerhans Glucagon Alpha cells Somatostatin Delta cells Rabbits used as models for Diabetes mellitus Normal glucose levels can be very high Stress response Non pathological glucosuria Spontaneous diabetes rare in rabbits Insulinoma reported
Endocrine Pancreas - Rodents
Diabetes mellitus common in Degus and Guinea Pigs
Rare but reported in Chinchillas
Degusdevelop spontaneous diabetes mellitus
Amyloidosis of the Langerhans islets
Cataracts common sequelae of diabetes in degus
Sudden onset
Avoid sugary treats/fruit esp in degus
Pituitary Gland
rodents
Typical trilobed mammalian Pituitary gland Growth Hormone Excess Gigantism Deficiency Dwarfism Thyroid Stimulating Hormone (TSH) Adrenocorticotrophic hormone (ACTH) Oxytocin Antidiuretic hormone (ADH) Prolactin (produced in hypothalamus & released by pituitary) Follicle stimulation Hormone (FSH) Luteinizing Hormone (LH)
Thyroid
rodents and rabbits
Largest of true endocrine glands
Bilobed on either side of trachea below larynx
Lobes connected by connective tissues isthmus
Produces thyroglobulins
Thyroxine
Regulates metabolism
Thyroid disease rare in rabbits
1-4% Guinea Pigs, 5th most common neoplasia
Rare but reported in Chinchillas
Parathyroid
rodents and rabbits
Two small oval glands in rabbit, on lobes of the thyroid
Four glands in many other mammals
Secretions:
Parathryoid hormone
Calcitonin
Calcium Homeostasis
Rabbits exhibit unique pattern of renal response to PTH
Thymus
rodents and rabbits
Unknown endocrine function
Thymus persists into adulthood in rabbits
Undergoes age related atrophy in rodents
It is a large bilobed gland in the upper chest region in front of heart and below the base of trachea.
Visible on normal thoracic radiographs
Its secretion stimulates metabolism, growth and helps in attaining sexual maturity
Lymphoid organ involved in immune function
Degus have double thymus with cervical and mediastinal lobes
Gonads
rodents and rabbits
Endocrine function in addition to gamete production
Testis
Testosterone secreted by the interstitial cells or cells of
responsible for the development of secondary sexual characters in male,.
Ovary
Oestrogen/oestradiol secreted cells surrounding the Graafian follicles
Responsible for the mature growth, development and maintenance of the female reproductive system
Stimulates the secondary sexual characters and also contributes to the sexual desire of the female.
Corpus Luteum
Progesterone suspends further ovulation during pregnancy
Maintains pregnancy and prepares uterine wall for embryo attachment
Heart – Rabbit
As observed in other small animals, the rabbit heart has 4 chambers - 2 atria and 2 ventricles separated by inter-atrial and inter-ventricular septa respectively.
The left ventricle is larger than the right.
The heart is the largest organ within the mediastinum but is relatively small in comparison to other species.
The rabbit heart represents only 0.20% of body weight, in contrast to the canine heart that is 0.76% of body weight.
The heart is located in the thoracic cavity with the apex (tip of the heart) directed backward and slightly to the left with the base directed forwards.
The heart is positioned more cranially than in dogs and cats, and auscultation will allow the rate, rhythm and presence of any murmurs to be noted.
By using the femoral artery, the pulse rate and quality can be appreciated.
The heart and great vessels are surrounded by lung tissue.
The cranial, middle, and accessory lobes of the lung surround the heart and form a well-defined pocket.
In many cursorial (legs adapted for running) lagomorphs, such as Lepus spp, an extended right cranial lobe is interposed between the sternum and the heart to cushion and provide protection to the heart, however this feature is lacking in Oryctolagus spp., possibly as a result of domestication.
Further physiological points that differentiate the rabbit heart from that of other small animals, include –
The aortic nerve has no chemoreceptors, but only baroreceptors, i.e. it does not have sensory nerve cells that are activated by chemicals, but only pressure-sensitive nerve endings, that stimulate reflex mechanisms that allow the body to adapt to changes in blood pressure by dilating or constricting the blood vessels.
The pulmonary artery and its branches are heavily muscular.
The coronary arteries, which supply the cardiac muscle and are given off from the aorta and can easily be compressed leading to ischaemia of the myocardium due to poor collateral circulation.
Heart – Guinea pig.
Occupying most of the small thoracic cavity, the four-chambered heart is surrounded by a two-layer pericardium within the mediastinum.
Externally, the thin-walled atria are separated from the ventricles by the coronary sulcus (groove) that contains the coronary veins and arteries.
The ventricles are separated dorsally and ventrally by two shallow interventricular sulci.
The guinea pig has a lower basal coronary blood flow and lower peak coronary blood flow in comparison to other species.
Well developed collateralization of the coronary arteries reduces the risk of myocardial infarction by acute coronary artery occlusion compared to other species.
Examination of the cardiovascular system in hystricomorph rodents adn rabbits
Use of a paediatric stethoscope is advised.
Because of the timid personality of RHr, the high sensitivity to stress, and the risk of self- induced injuries, animals must be restrained carefully.
To prevent excessive stress that may result in the aggravation of clinical signs or misinterpretation of physical examination findings, the animal is restrained gently in sternal recumbancy and examined in a quiet room with reduced external stimuli.
Animals will become increasingly stressed the longer a physical examination continues, so to attain the truest values for respiration and heart rate, these should be obtained at the beginning of the consultation.
Sedation may be required to prevent excessive stress and the risk of self-injury.
Heart rates towards the higher part of the range should be expected upon auscultation because of increased sympathetic tone secondary to stress
Blood movement through the rabbit heart.
Rabbits have a left cranial (precaval) vena cava in addition to the right cranial vena cava which terminates in a large coronary sinus that also drains the cardiac veins.
The presence of a left cranial vena cava results in an extremely large coronary sinus, which in turn disrupts most of the atrial septal structures cranially.
The right atrium receives deoxygenated blood from the two cranial and the caudal venae cavae.
Once in the atrium, deoxygenated blood flows to the right ventricle through the right atrioventricular valve or tricuspid valve.
The tricuspid valve is composed of only two cusps and is often described as a distinctive attribute of the rabbit the rabbit, however, this feature is shared by many species
The right ventricle ejects blood via the pulmonary artery into the lungs to be oxygenated.
Cusp valves separate the ventricular chambers from the pulmonary artery and the aorta.
The newly oxygenated blood flows out of the lungs and into the left atrium through the pulmonary veins.
From the left atrium, blood flows into the left ventricle and into the aorta to be distributed to the rest of the body.
The aorta has a rhythmic contraction that is neurogenic in origin.
Arteries – Rabbit.
Though the rabbit has a right and left coronary artery, most of the heart is supplied by the left coronary artery and its branches.
Branches from the septal artery are perpendicular to its long axis and ascend across the right ventricular septal endocardium to the His bundle and the AV node - this sequence is opposite from that of humans.
The internal carotid artery is relatively small despite being the main blood supply source to the brain.
The pulmonary artery is heavily muscled compared to other species.
Arteries - Guinea pig.
Unique features of the circulatory system include the caudal cerebral artery arising between the basilar and internal carotid arteries.
The internal carotid arteries do not supply a significant amount of blood to the cerebral arterial circle however, paired internal ophthalmic arteries do provide major collateral input.
Another unique feature that deviates from the normal mammalian vascular pattern is the bronchoesophageal artery which originates from the right costocervical, the right internal thoracic, or the brachiocephalic trunk instead of from the aorta.
In the guinea pig, the pulmonary trunk differs from the aorta in that it is made up of short irregular branching elastic fibres interspersed with smooth muscle and collagen.
The pulmonary artery and its branches are heavily muscled and the lumen size of the pulmonary arteries changes abruptly at areas of branching.
Individual variation.
In some guinea pigs there may be 2–3 pairs of renal arteries located cranially and caudally to each kidney arising as separate arteries.
The testicular artery arises from the aorta supplying the testis and epididymis.
When two renal arteries are present bilaterally, the testicular artery may originate from the renal arteries, arise between them from the aorta or arise caudally to the caudal renal artery.
In the female, the ovarian artery has a similar origin to the testicular artery - it divides into several branches supplying the oviduct, ovary, and uterus.
When two renal arteries are present bilaterally, the ovarian artery may originate from the aorta between the two renal arteries, directly from the caudal renal artery or caudal to the renal arteries at the aorta with the left ovarian artery originating from a left caudal renal branch
Arteries – Chinchilla.
Internal carotid arteries are absent as the blood to the brain is supplied solely by a vertebral-basilar artery system.
The chinchilla has only a left coronary artery.
The left coronary artery arises from the aorta at the sinus of the aorta and courses towards the coronary groove, eventually dividing into paraconal, interventricular, and circumflex branches.
Arteries - Degu.
A systematic study of the vasculature of degus has not been conducted.
The arterial anatomy of the degu is similar to that of the guinea pig as both degus and guinea pigs have a coeliacomesenteric trunk arising from the aorta that is the origin of the cranial mesenteric and celiac arteries.
The brain is supplied by the vertebral artery.
Blood sampling in rabbits and hystricomorph rodents
Common sites used for venepuncture in rabbits include the jugular vein, the lateral saphenous vein, the cephalic vein, the marginal ear vein and the central ear artery.
The cephalic vein is usually preserved for IV catheter placement.
Smaller samples can be drawn from this site, but excessive suction can cause collapse of the vessel.
The marginal ear vein can also be used for catheter placement.
The central auricular artery has been used for collecting arterial blood.
Restraint for blood sampling in rodents may be stressful and anaesthesia or sedation are often required.
The cranial vena cava is the largest easily accessible vessel in rodent species but may result in pericardial sac penetration and bleeding into the thoracic cavity if an inappropriate technique is used.
The injection site is just cranial to the first rib, 0.3cm to 0.8cm lateral to the manubrium (upper most segment of the sternum) when the animal is in dorsal recumbency.
In species with an underdeveloped clavicle, such as in guinea pigs and chinchillas, the needle is inserted cranial to the manubrium and first rib.
Jugular venepuncture can be challenging in certain species,
Those that have short, thick necks with large fat coverage, making the veins difficult to locate, especially in guinea pigs.
In rabbits with large dewlaps.
The lateral saphenous and the cephalic vein may be used, but can be difficult to locate, collapse easily and may yield only minimal blood volumes.
Rabbit - Nasal passages and sinuses
As obligate nasal breathers any impediment to clear airflow through the nares and nostrils can lead to marked dyspnoea, which in other species, would simply be resolved by mouth breathing.
It is also very easy for infection to pass caudally and up the Eustachian tube to the middle ear-leading to otitis media, with extension to an otitis externa or interna, or to pass down the trachea, leading to pneumonia.
Air enters via the external nares, passes the alar folds and into the nasal chambers which are divided by a vertical cartilaginous septum and separated from the oral cavity by the hard palate.
The nasal cavity is lined with a protective layer of mucus that entraps foreign particles and bacteria, prevents water loss and enhances the sense of smell.
Each cavity consists of the dorsal and ventral nasal conchae (turbinates) and, caudally, the endoturbinates.
Ostia (openings) connect these to the paranasal sinuses – the conchal (ethmo) sinus dorsally and the maxillary sinus laterally.
The incisor and pre-molar teeth roots are closely associated with the nasal chambers and minimal bone separates the roots and the nasal chambers so dental pathology is often linked to nasal pathology.
The sinuses are a connected system of hollow cavities, lined with mucosa, in the skull which are normally empty except for a thin layer of mucus.
The maxillary sinuses in the rabbit are large and have interconnected anterior and posterior sections.
The maxillary sinus opens laterally to the endoturbinal through an oval ostium.
Ethmoid sinuses in rabbits are less developed when compared to humans and are located medial to the endoturbinate.
there is no frontal sinus.
Guinea pig – nasal passages and sinuses.
The nasal cavity extends caudal from the nostrils to the choanae and is bounded dorsally by the nasal bones and laterally and ventrally by the incisive and maxillary bones.
The nasal cavity is rectangular when viewed laterally but T-shaped on cross-section due to its broadness dorsally and extreme narrowness ventrally.
The lining changes abruptly to ciliated pseudostratified columnar epithelium with goblet cells within the nasal cavity.
There are two recesses in the nasal cavity, the rostral recess and maxillary recess.
Multiple sources state that the guinea pig lacks a maxillary, frontal, and sphenoid sinus, although others may refer to the maxillary recess as the maxillary sinus.
Variations in the number and position of the ethmoturbinates have been documented, with four being the most common.
The medial or septal wall has a large defect where the two nasal fossa are joined just rostral to the defect in the septum is a slight bulge which is the area of the vomeronasal organ associated with pheromone detection.
The choanae are the caudal terminations of each nasal fossa and communicate with the nasopharynx.
Rabbit - Oropharynx, Larynx and Pharynx.
The nasal cavity progresses caudally where the epiglottis is engaged over the soft palate, allowing unobstructed airflow into the larynx.
The rabbit epiglottis is a relatively large structure that lies dorsal to the soft palate, thereby allowing air directly from the nasopharynx to the larynx and trachea without entering the oral cavity.
It is this anatomy that makes the rabbit an obligate nose-breather and is important when attempting intubation of the trachea.
The glottis (opening between the vocal folds in the larynx) of the rabbit is small and with the relatively large tongue, the glottis remains well covered.
intebating rabbits
Rabbits are prone to laryngospasm and intubating them can be a challenge.
The rabbit’s glottis is small, its tongue is so shaped that it hides the larynx, and its larynx is smaller than its trachea.
The rabbit’s trachea is long and bifurcates into main stem bronchi at an angle such that accidental intubation of one bronchus is unlikely.
The vocal cords of the rabbit are very strong and can easily deflect the tip of the endotracheal tube into the oesophagus, insertion of the tracheal tube therefore has to occur during inspiration, when the vocal cords are open.
intubating Guinea pigs/chinchillas
Mechanoreceptors are present in the upper airways that respond to touch (e.g. endotracheal tube) with strong laryngeal spasm.
Guinea pigs and chinchillas are generally harder to intubate than rabbits, this is due in part to the small size of their laryngeal openings.
Guinea pigs and, to a lesser extent, chinchillas have a narrow palatial ostium (small opening in the soft palate connecting the oropharynx with the pharynx) formed by the soft palate, palatoglossal arches, and tongue.
Tracheal strictures - endotracheal intubation can cause trauma to the tracheal lumen which may lead to a stricture or narrowing of the trachea.
Narrowing of the trachea can lead to dyspnoea, respiratory tract obstruction and death.
Guinea pig – nasopharynx and larynx.
The trachea is well innervated but the small airways have little to no innervation.
The nasopharynx is relatively short and the soft palate forms the floor of the nasopharynx and is continuous with the base of the tongue.
The openings of the Eustachian tube appear as two prominent slit-like openings dorsal to the soft palate on the dorsolateral walls of the nasopharynx.
The laryngeal cavity is divided into three portions - the vestibule, the glottis, and the infra-glottis.
The guinea pig has no laryngeal ventricle and the vocal cords are small and poorly developed, however, the guinea pig has the ability to vocalize and can produce numerous sounds.
Trachea - Compared to other mammals, the guinea pig has the most prominent smooth muscle in the distal bronchi and the muscle is spirally arranged.
Lungs – rabbit.
The lungs of the rabbit are relatively smaller than those predicted for its body mass, possibly as a consequence of domestication.
Respiratory movement in rabbits is mainly diaphragmatic rather than due to the action of the intercostal muscles.
Lungs are divided into cranial, middle, and caudal lobes with the right caudal lung lobe additionally divided into the lateral and medial lobes.
The right cranial lung lobe is larger than the left cranial lung lobe due to the presence of the heart in the left pleural cavity.
The sole blood supply to the pleura is the pulmonary artery.
Extensive anastomosis with the pulmonary artery occurs at the level of the hilus in the rabbit, unlike in the dog, cat, or monkey.
In rabbits the bronchial artery extends to the third division of the bronchi.
There is a lack of collateral blood supply beyond this area, which places the rabbit at serious risk if an obstruction to the pulmonary artery occurs
Lungs – Guinea pig, Chinchilla and Degu.
Lung anatomy is similar in the Guinea pig, chinchilla and degu and showing some differences to the rabbit.
The larger right lung consists of four lobes - cranial, middle, caudal and accessory each separated by deep fissures.
The right cranial lobe is the smallest.
The right middle lobe is caudal to the cranial lobe and its medial surface has a concave cardiac impression.
The right caudal lung lobe is the largest and has a concave diaphragmatic surface and extends to the eighth rib.
The accessory lobe has an irregular shape with a deep notch on its ventral border for the caudal vena cava and a concave diaphragmatic surface
The left lung consists of three lobes - cranial, middle, and caudal.
The left cranial lobe has an intralobar fissure that divides it into a smaller cranial segment and larger caudal segment.
The medial border is deeply concave to accommodate the heart.
The small left middle lobe has a shallow medial notch for the oesophagus and a concave diaphragmatic surface.
The large left caudal lobe has a concave medial border in contact with the middle lobe.
There are no intralobular septa in the lung or secondary individual lobulations.
Due to the lack of septation between lobules there exists extensive collateral ventilation
describe the classic triad as a frameworks for thinking about causality
agent- host susseptability- enviroment
Well-suited to communicable disease
Encourages thinking about inter-relationship of agent, host, environment
describe the Sufficient component-cause model
(causal pies)
as a frameworks for thinking about causality
factors adcu vs abfg vs adeh= A is a factor requred for disease
Multicausality
Interaction / accumulation of component causes over time
Understanding multiple pathways to disease
describe the Potential outcomes framework / counterfactual theory
as a frameworks for thinking about causality
think about the road not taken- eg. 20/100 dogs died after a procedure. if those dogs had not had that procedure 18 would still have died but 100 days later 5 more would have died
Imagination - what if?
Narrower focus on defining the effects / interventionist
Links to powerful study design tools like directed acyclic graphs (DAG)
Epidemiological studies produce evidence typically in the form of an
association or correlation
Whether these associations/correlations represent a cause-effect is a matter of inference, i.e. judgement
There is nothing about the statistical association between a determinant and an outcome that can ‘prove’ that a relationship (association) is causal
describe designs for studies detailing prevention and treatment
an exposure is assigned
it is an experemental study
if randomly assigned it is a Randomised controlled trial
if not randomly assigned it is a non-Randomised controlled trial
describe designs for studies detailing burden and impact
no exposure is assigned
it is an observational study
there is no comparison group
it is a descriptive study e.g Cross-sectional (prevalence) survey, Ecologic study, Case report / series
describe designs for studies detailing causes and prognosis
no exposure is assigned it is an observational study there is a comparison group it is an analytical study with a direction exposure-> outcome= cohort study exposure
Bradford-Hill’s “aspects to consider” when trying to infer causality from an association
- Strength. Very strong associations will generally be harder to explain away by confounding or bias.
. Consistency. An association that is repeatedly observed by different research teams under different circumstances may be less likely to be produced by confounding or bias. - Specificity. A cause leads to a single effect not multiple effects. [Not to be over-emphasised.]
- Temporality. We should be confident that the exposure preceded the outcome.
- Biological gradient. Is there a dose-response, such that higher levels of exposure have a greater effect?
- Plausibility. Is a causal connection biologically plausible [depends on the state of biological knowledge at the time]
- Coherence. Does a cause-effect interpretation seriously conflict with other established facts about the disease?
- Experimental evidence. Does removal of the cause prevent (some cases of) the disease? [may not be feasible or ethical]
- Analogy. Can we draw any parallels?
Rabbit Skin
Thin delicate skin
Tears very easily
Skin on the neck is loose and pendulous
Dewlap in sexually mature females of some breeds
Blood vessels immediately under the dermis
Dorsal skin thicker than ventral skin
Skin thinner in wild rabbits than domestic/lab counterparts
Calcium
Vitamin D activation
Rabbit UV requirement
Thermoregulation
No sweat glands
Don’t pant
Heat exchange in the ears
Large arteriovenous anastomotic system
Very little fur
Can stretch and contract pinnae to increased and decrease surface area
Water homeostasis
Nasal glands
Moisten inspired airRabbit kits fully furred by about 12-14 days
Rabbits are furred all over except for:
Nose
Scrotum
Inguinal region
Hair grows in waves from ventrum and grows dorsocaudally
No footpads – thickly furred plantar and palmar surfaces
Breeding females pull fur for nestbuilding
Dewlap, ventrum
rabbit hari types
Hair follicles sit in bundles One central primary hair follicle Single longer rectrix guide hairs Long and rough 3-4 cm long 2-4 Lateral primary hair follicles Numerous tectrix barbed hair (guard/barb hairs) 3-3.5cm long Form major part of the coat 20-50 secondary down hair follicles 90-95% of hairs 2-3cm long Undercoat or down hairs Insulating coat for thermal protection Ratio of secondary to primary hair follicles less in pet rabbits cf wild
describe the fur of normal rabbit breeds compared to rex breeds
Over 60 fancy and fur breeds Fur Normal Undercoat and projecting guard hairs Each follicle contains ~ 14 hairs 1-1.5” length Rex Short guard hairs don’t project beyond undercoat Each follicle contains up to 50 hairs ½- 7/8” length Velvety coat
Rabbit Vibrissae
Vibrissae (whiskers) grow from special hair follicle Blood sinus capsule Sensory nerve innervation 100-00 efferent nerve cells/follicle Trigeminal nerve Rabbit whiskers Mouth, cheeks, nose, above eyes Same length as body width Sensory tool for gauging borrow widthEye protection from debris
Dew Lap
Sexually mature females Especially if not neutered/early Certain breeds Mores distinctive in larger breeds Facilitates nest building Issues Can compromise grooming Esp if overweight Moist dermatitis Dental disease Poor hygiene Waterbottle prefereable to bowl
Lop Eared rabbit Breeds
Normal ‘prick eared’ rabbits Three interlocking auricular cartilages Rigid support for erect ear Lop Forms Gap between second and third cartilages Soft tissue only Allows ear to fall & closes ear canal Prevents draining of cerumen Infection/pressure from cerumen build up Brachycephalic breeds Further reduced draining via eustachian tube Exaggerated ear sizes Welfare implications
Rabbit Scent Glands
Present in males and females Three scent glands Chin glands Specialized submandibular glands Open onto the ventral surface of the chin Anal glands Inguinal glands Pocket-like perineal glands – modified sebaceous glands Dorsal to urogenital opening lateral to anus Open into perianal pouches Characteristic rabbit odour Males mark > females Dominant rabbits mark > submissive
non sent glands in rabbits
Sebaceous Glands
large glandular, branched alveoli-like saccular glands
Located in upper part of the hair follicle by a small duct.
secrete oily secretion called sebum via small duct
lubricate the hair makes the skin waterproof and greasy.
Sebum is bacteriocidal in nature.
Meibomian Glands
Eyelid margins beneath conjunctiva
Open on medial eyelid
Modified sebaceous glands
Oily secretion for eyelash lubrication
Harderian Glands
Bilobed tubuloalveolar gland
Located infraorbitally between eye ball and ventromedial orbit
Associated with nictitating membrane
Secretes lipid via single duct
Lubrication of ocular surface and NM
Rabbit Moult & Shedding
Kit’s coat replaced by transitional coat ~ 5 months
Biannual moult
Usually Spring and Autumn
Can appear to be continuous
House rabbits don’t follow seasonal pattern
Moult normally starts on head and progresses caudally and ventrally
Tide Line
Darker skin where new coat growing
Flanks and ventrum last places to be cleared
Pregnancy moult (also (pseudopregnancy)
Easy epilation of hair on ventrum, chest and dewlap for nest building
Grooming pet rabbits (esp long haired
Subcutaneous injections in rabbits
Most parenteral medications and fluids Well tolerated Can result in a skin reaction Especially vaccines or some antibiotics Older rabbits may have a thick dermal shield Can make SQ injections difficult 10-20ml/kg subcutaneous fluids Loose skin over scruff usual injection site Can inject over thoracic skin
Guinea Pig Integument
Unusually large epidermis relative to dermis
Results in higher metabolic activity cf other species
Hair consists of large guard hair
Finer undercoat hair
Typed according to length,
Various colours/patterns/lengths
Each follicle has androgen dependent sebaceous
gland
Most abundant along dorsum and around anus
Hairless areas
External orifices, inguinal mammary glands, caudal to ear pinna
No sebaceous glands behind ear
Various different coats
Hairless breeds
Guinea Pig Scent Gland
Grease Gland
Glandular area elevated with pigmented skin
Greasy fur
More developed in the male
Can result in greasy matted dorsum in older males/grooming deficiencies
Hairless areas
External orifices, inguinal mammary glands, caudal to ear pinna
No sebaceous glands behind ear
Degus and Chinchilla’s don’t have comparable glands
Urine scent marking predominates
Chinchilla Integument
Extremely dense fur Hairs 2-4cm long 3 colour areas of hair Hair arranged in clusters Average of 50-60 hairs (max 70) 1 guard hair 1 sebaceous gland 2 lateral bunches of ‘wool’ hairs 3-4 sebaceous glands Single erector pili muscle Require regular dust baths Fur slip
Vibrissae (Hystricomorphs)
Guinea pigs & Degus Similar whisker structure and function to rabbits Chinchillas Exceptionally long Can be > 1/3 of total body length Crepuscular – poorer eyesight Spend time in borrows underground Social/status role
non scent Rodent glands
Harderian Glands Guinea Pig Very large gland occupying retrobulbar space Lobulated Single excretory duct Chinchilla Oval non lobulated gland Third eyelid is rudimentary
orbital venous plexus in rabbit
Extensive orbital venous plexus
can lead to exophthalmos if engorged as a stress response/disease due to location in relation to the caudal globe
Incr MAP/Decr drainage
Difficult to ligate during enucleation – be aware!
Physiological engorgement of this plexus can be seen as a stress response in some rabbits
shorten the axial length of the globe further, exacerbating the axial myopia, but can also lead to exophthalmos.
Increase peripheral vision and widen the field of binocular overlap, a potentially useful visual strategy for identification of distant predators
rabbit eye anatomy
Large cornea, occupies 30% of the globe Cornea significantly thinner than in dogs and humans – clinically significant for ocular surgery or measuring IOP. 386 +- 20um thick Dog 562 +- 6um Human 540um +- 20um G pig 227 +- 14um Chinchilla 340 +/-4um
The lens is spherical and large
Dorsoventrally ovoid pupil – enhances dorsal visual field
Pupillary muscle fibres allow more rapids and complete dilation
The ciliary body is small and poorly developed
The globe is shorter in the AP axis
suggests limited need for accommodation (near and far focus)
Hypermetropic (long-sighted) peripheral vision and strong axial myopia (short sightedness) centrally
Peripheral vision used for detection of distant predators, while central binocular vision is used for identification of food sources.
normal heart rate of pigs
90-100 bpm
average resperation rate of pigs
10-20
averege temp of pigs
38.5-40
pig dentition
3143/3143
poits to sample blood in the pig
coccygeal vein, jugular vein and lateral auricular vein in adults
crainial vena cava in piglets
Poikilotherm
adapts to environment, temperature fluctuates, cheap
Homotherm
warm blooded- constant body temperature, independent of environment- active
Thermoneutral zone
The range of temperature in which a homeotherm can regulate its body temperature by adjusting heat loss at negligible energy cost.
•Within the thermoneutral zone:
–Metabolic heat production and energy expenditure are minimal
–Most production processes are most efficient
–The animal is thermally comfortable
describe bacteria
Unicellular Prokaryotic Variety of shapes Peptidoglycan cell wall Reproduce by binary fission Variety of sources of nutrition
bacterial Pili
Pili or fimbriae are protein structures that extend from the bacterial cell envelope for a distance up to 2 μm They function to attach the cells to surfaces. E. coli cells can have up to 300 of these organelles
bacterial flagella
Corkscrew-shaped
Protein fibres
Used for cell movement
Only observable with staining
Composed of filament, hook and basal body
Generates propeller-type rotation
Important in classification of strains/serotypes
Features of bacterial cells – glycocalyx
Sticky layer that covers cell wall Polysaccharides and proteins Capsule = bound to cell Thinner = slime layer Various roles in virulence as well as protection against desiccation Aids attachment to host Avoidance of immune cells Creation of biofilms
Features of bacterial cells – cell membrane
Cell membrane carries out ATP synthesis
Generation of proton gradient outside cell membrane
Proton motive force drives ATP synthesis
bacterial Cell wall - peptidoglycan
peptidoglycan (murein) is an essential and specific component of the bacterial cell wall found on the outside of the cytoplasmic membrane of almost all bacteria . Its main function is to preserve cell integrity by withstanding the turgor. Indeed, any inhibition of its biosynthesis (mutation, antibiotic) or its specific degradation (e.g. by lysozyme) during cell growth will result in cell lysis. Peptidoglycan also contributes to the maintenance of a defined cell shape and serves as a scaffold for anchoring other cell envelope components such as proteins and teichoic acids . It is intimately involved in the processes of cell growth and cell division.
has a backbone of NAM and NAG linked to other backbones by peptide cross-bridges and vertically by side peptides
cell wall of gram positive bacteria
comprised of multiple peptidoglycan layers combined with teichoic acid molecules
cell wall of gram negative bacteria
thin peptidoglycan layer. an outer membrane overlies the peptiglycan in the periplasm and the membrane contains porin protiens. the outer half of the outer membrane contains lipopolysaccharide lps
Gram stain
Crystal violet added to a heat-fixed bacterial smear stains all cells purple (primary stain);
After washing, the smear is covered with iodine which forms a purple CV-I complex in the cytoplasm;
Washing the slide with alcohol-acetone ( a decolouriser) disrupts the outer LPS layer of G-ve cells and the CV-I complex is washed away through the thin peptidoglycan; these cells are then colourless until counterstained with safranin (pink);
Alcohol-acetone does not wash the CV-I complex out of G+ve cells (thicker peptidoglycan), so they remain purple.
Proteobacteria
Largest and most metabolically diverse phylum; include 1/3rd of all characterised species of bacteria
Contain most bacteria of medical, industrial & agricultural significance
All Gram-negatives with wide diversity in:
Energy-generating mechanisms – chemolithotrophs, chemo-organotrophs & phototrophs
Relationship to oxygen – anaerobes, microaerophiles & facultative aerobes
Cell shape – straight/curved rods, cocci, spirilla, filamentous, budding & appendaged forms
Alphaproteobacteria
ca. 1000 species; second largest class
Contain most Proteobacteria that grow with very low levels of nutrients - oligotrophs
10 orders
Agriculturally important bacteria capable of nitrogen fixation in symbiosis with plants
Several human and animal pathogens; most are obligate intracellular parasites
Rickettsiales
Obligate intracellular parasites
Reside within phagosome of infected host cell
Key genus: Rickettsia
Invades vascular endothelium
Requires host ATP and nutrients
Responsible for high mortality rates in humans and animals
R. rickettsia (Rocky Mountain spotted fever)
Transmitted from arthropods (tick bites)
Rhizobiales
Genus Brucella
Localised in intracellular compartments of phagocytic, reticuloendothelial and specialised epithelial cells
Pathologic effects in reproductive tissues
Some zoonotic Brucella spp.
Vaccination programmes for B. abortus and B. melitensis
Detection via serology or molecular-based tests
‘Test and slaughter’ approach to control
Betaproteobacteria
Over 75 genera and 400 species
Include pathogenic species as well as those important in agriculture and natural ecosystems
Bordetella sp. cause destruction of ciliated respiratory epithelium (rhinitis, sinusitis, tracheitis) leading to pneumonia
Burkholderia sp. cause pyogranulomatous lesions
Gammaproteobacteria
Largest subgroup of proteobacteria (1500 species) Contains many human and animal pathogens Enterobacterales Pasteurellales Pseudomonadales
Bacterial cell cycle
Cell growth phase
Cell mass and size increase.
Special enzymes break wall to allow expansion.
DNA replication phase
Chromosome is copied in preparation for division.
Cytoskeleton aids separation of chromosomes
No requirement for microtubular spindle apparatus or complex patterns of arrangement
Binary fission phase
Asexual reproduction
Septum divides enlarged cell into two identical daughter cells.
Replicating chromosomes attach to cell membrane in separate locations
Cell continues to elongate pulling two identical chromosomes further apart
Invagination of cell wall and membrane as new material is laid down
Pulled together by fission ring
Completion of new cell membrane and cell wall
Septum material can dissolve slowly
Daughter cells may not separate straight away
Forms characteristic pairs, chains or clusters
Each daughter cell then enters cell cycle
oligotrophs
An oligotroph is an organism that thrives in an environment that offers very low levels of nutrients.
Most bacteria are oligotrophs
Spend majority of life in nutrient-limited state
Infrequent division
Bacterial growth curve- lag phase
- Adapting to new environment
- Cell growth processes
- Preparation for binary fission
- Length will depend on metabolic activity of the population
Bacterial growth curve- log phase
- Exponential growth
- Requires optimal metabolic and physiological conditions
- Rapid increase in number of cells
Bacterial growth curve- stationary phase
Population growth is arrested
Limited by nutrient availability
Bacterial growth curve- declien phase
Limited nutrients in closed system
Cells start to die off
Balanced state of cell death
Quorum sensing
Quorum sensing (QS) is a communication mechanism between bacteria that allows specific processes to be controlled, such as biofilm formation, virulence factor expression, production of secondary metabolites and stress adaptation mechanisms such as bacterial competition systems including secretion systems (SS)
persister cells
Bacterial populations produce persisters, which are phenotypic variants of the wild type whose function is survival. Persisters are dormant, non-dividing cells that exhibit multidrug tolerance and survive treatment by all known antimicrobials.
Dormancy - endospores
Produced in response to nutrient limitation (starvation)
Complex program of gene expression
Single endospore created by mother cell
Represents growth-arrested stage
An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Firmicutes. … In endospore formation, the bacterium divides within its cell wall, and one side then engulfs the other. Endospores enable bacteria to lie dormant for extended periods, even centuries.
Thick peptidoglycan layer protects spore from outside environment
Survives desiccation, extreme temperatures, chemical treatments and radiation
Germination of endospores of B. antracis (anthrax), Clostridium sp. (botulism; tetanus) upon introduction to the body
Optimal growth is dependent on what several physical and chemical factors:
Temperature pH Osmotic pressure Carbon Oxygen
Bacterial Growth conditions: temperature
Optimal growth temperature Supports best growth Shortest generation time Temperature range of about 30°C Minimum growth temperature Lowest temperature at which slow growth still possible Maximum growth temperature Must stay below this or death results Five groups of organisms: Psychrophiles: range 0°C to 20°C Psychrotrophs: range 4°C to 39°C Mesophiles: range 10°C to 45°C Thermophiles: range 40°C to 70°C Hyperthermophiles: range 80°C to 115°C
Bacterial Growth conditions: pH
Acidophiles: Grow best at pH below 5 Valuable in food/dairy industries Neutrophiles: Majority of species, including most bacterial pathogens Narrow range toleration Alkaliphiles: Grow best at pH above 8
bacterial Growth conditions: osmotic pressure
Extreme halophiles Require 20–30% salt Halophiles Some grow in 2–5% salt Others grow in 5–20% salt Halotolerant Can grow in ≤8% salt Non-halophiles Grow optimally <2% salt
Bacterial Growth conditions: carbon
All life on Earth is carbon based
Carbon is required to build organic molecules necessary for life
Growth media must contain a carbon source
Bacterial Growth conditions: oxygen
Many bacteria require oxygen for growth
Some can survive in very low oxygen
Some are killed by oxygen
Some can grow with and without oxygen
Bacterial Growth conditions: other elements
Nitrogen, sulfur, and phosphate
Needed for growth and reproduction
Proteins contain nitrogen and sulfur.
Amino acids contain nitrogen and phosphorus.
Most nitrogen and sulfur from breaking down proteins into amino acids;
Some species get ammonium or nitrate ions from soils
Bacterial Growth conditions: growth factors
Growth factors must be obtained from the diet because they cannot be made by the organism
Often includes essential vitamins and amino acids
Bacterial chromosome
Single circular chromosome
Circular molecule of DNA with associated proteins
Attached at one or several points to the plasma membrane
Looped and folded
DNA of E. coli is 1mm long which is 1,000 times longer than the entire cell
Only takes up 10% of cell’s volume
DNA is supercoiled
Bacterial plasmids
Many bacteria contain plasmids
Plasmids contain their own origin of replication but rely on chromosomally encoded enzymes for replication
Most are expendable – essential genes for growth encoded on chromosomes
Thousands of different ones are known - >300 in E.coli alone
Stable, nonessential double-stranded DNA outside the nucleoid
F plasmids
Genes for proteins and pili
R-plasmids
Genes for antibiotic resistance or poison resistance
Col plasmids
Genes for bacteriocins
Virulence plasmids
Genes for toxins and other factors
Vary in:
Size - 1 kbp – 1 Mbp; usually <5% size of chromosome
Copy number – how many copies in a single bacterial cell (1-1000)
Host range – how many different types of bacterial cells they can exist/function in (1-1000)
Number and type of genes encoded (5-100)
Some organisms contain several different types of plasmid e.g. Borrelia burgdorferi contains 21 different linear/circular plasmids
Bacterial plasmids - resistance
Often carry genes that influence host cell physiology
Resistance or R plasmids confer resistance to antibiotics or growth inhibitors
May encode several antibiotic resistance genes or bacterium may contain several different R plasmids
Plasmid R100 encodes resistance to sulphonamides, streptomycin, spectinomycin, fusidic acid, chloramphenicol, tetracycline & mercury
Virulence factors are often plasmid-encoded, including the ability to attach to/colonise host tissue and the production of toxins, for example
Bacteriocins are proteins that confer immunity on the host and can also be plasmid-encoded
bacterial Gene transfer
Vertical gene transfer: during reproduction (cell division) between generations (i.e. parent to offspring)
Lateral (horizontal) gene transfer: between cells of the same generation:
- Conjugation - Transformation - Transduction
Conjugation
Mechanism of genetic transfer that requires cell-to-cell contact
Plasmid-encoded mechanism that can mediate DNA transfer between unrelated cells or even different genera
Donor cell: contains conjugative plasmid
Recipient cell: does not contain plasm
gene transfer- Transformation
Genetic transfer process by which free DNA is incorporated into a recipient cell and brings about genetic change
Several prokaryotes are naturally transformable - a cell that can take up DNA and be transformed is said to be competent
Competence is genetically determined and regulated – competence specific proteins include: a membrane-associated DNA binding protein; a cell wall autolysin; and various nucleases
Acinetobacter, Bacillus, Streptococcus, Haemophilus, Neisseria and Thermus – naturally competent/easy to transform
Escherichia coli / other gram-negatives are not
gene transfer- Transduction
Transfer of DNA from one cell to another by a bacteriophage.
Occurs naturally in many genera of bacteria e.g. Escherichia, Pseudomonas, Salmonella, Staphylococcus
Not all bacteria are transducible and not all phages can transduce but phages outnumber prokaryotes by 10-fold
Examples of genes transferred via transduction include many antibiotic resistance genes in Salmonella enterica serovar Typhimurium, Shiga-like toxin genes in E. coli and virulence factors in Vibrio cholerae
bacterial mutation
A mutation is a permanent and heritable change or disruption in the base sequence of the genome i.e. a change that is passed from the mother cell to daughter cells.
Can be:
Spontaneous: occur in the natural environment without the addition of mutagens (agents that cause mutations) – occur at a low rate, but the high rate at which many prokaryotes divide means that they can accumulate very rapidly
Induced: created by the addition of mutagens
Spontaneous mutations = random natural changes to DNA
Errors made and not repaired
One event per 106 or 1010 cycles of binary fission
Induced mutations = changes produced by external physical or chemical agents called mutagens
Physical example: radiation
Chemical example: nitrous acid
Bacterial Mutation – base pair substitution
One base in the DNA sequence changed to another base
Transcript affected too
Silent mutation = amino acid sequence not affected
Due to redundancy of code
Missense mutation = mutated codon calls for incorrect amino acid.
Nonsense mutation = mutated codon is now a stop codon.
Bacterial Mutation – insertion or deletion
Inappropriate number of bases in a DNA sequence following mutation
Affects entire reading frame of 3-letter codons after the point of change
Frameshift mutation
Potential catastrophic change in functionality of protein
Mobile bacterial genetic elements
Discrete segments of DNA that move as units from one location to another within other DNA moleculesTwo major types of transposable element in bacteria:
Insertion sequences (IS)
Transposons
Always found inserted into another DNA molecule (plasmid, chromosome or viral genome) and do not possess their own origin of replication – only replicate when host DNA replicates
Transposable elements can interrupt the sequence of essential genes when they move.
Can be prime force behind spontaneous mutations
Can move from:
Chromosome to chromosome
Chromosome to plasmid
Plasmid to chromosome
Plasmid to plasmid
Between unrelated species
Spread antibiotic resistance
Antibiotic resistance – replica plating
Allows visual confirmation of mutations for antibiotic resistance
When strains cultured on media containing antibiotics:
Only resistant strains can grow; sensitive (wild-type) strains will die.
Culture media
Culture media contain nutrients that promote cellular growth and reproduction:
Liquid media = broths
Tubes or flasks
. Solidifying agent agar used for deeps, slants, and plates
Agar is derived from red algae
Non-nutritive so not consumed
Used to examine colony characteristics
Microbes vary in nutritional requirements.
No single medium supports the growth of all microbes.
Chemically defined medium
Known chemical composition and amounts of all ingredients
Complex medium
Chemically undefined
Contains plant or animal digests or yeast extracts
Widely used in labs
name the components, uses and examples of slective medium
components: Growth inhibitors
Uses: Certain species are inhibited, while others are able to grow
Examples:Mannitol salt agar for Staphylococcus
name the components, uses and examples of differntial medium
components:Dyes or indicator systems
Uses:Visual difference between microbes is readily observable
Examples: MacConkey agar for gram-negative bacteria
name the components, uses and examples of enriched medium
components:Special nutrients
Uses:Fastidious microbes supported by addition of specific growth factors
Examples: Blood agar for streptococci; chocolate agar for Neisseria
Xylose lysine deoxycholate (XLD) agar
Xylose Lysine Deoxycholate (XLD) Agar is a selective medium for the isolation of Salmonella and Shigella spp from clinical specimens and food samples. XLD Agar was originally formulated by Taylor for the isolation and identification of Shigella from stool specimens.
XLD Agar is both a selective and differential medium.
Eosin methylene blue (EMB) agar
EMB is a selective, differential agar medium used for isolation of gram negative rods in a variety of specimen types. It is used frequently in clinical laboratories.
Gut dysbiosis
term for a bacterial imbalance within the digestive tract.
gut microbiome
composed of bacteria, archaea, viruses, and eukaryotic organisms that reside in the gastrointestinal tract, and which relate with the host in a symbiotic fashion. For example, bacteria in the guts produce short-chain fatty acids (SCFA) that nourish the intestinal epithelium, while the epithelium produces mucus that feeds beneficial bacteria.
The gut microbiome contributes with metabolic functions, protects against pathogens, educates the immune system, and, through these basic functions, affects directly or indirectly most of our physiologic functions. Serotonin, a neurotransmitter, is mostly produced in the intestine, which has led to the development of the gut-brain axis concept (1). A healthy and stable microbiome can simultaneously act as pro- and anti-inflammatory, keeping a balance to prevent excessive inflammation while still being able to promptly respond to infections
Pathogenicity
Pathogenicityis the ability to produce disease in a host organism
Microbes express theirpathogenicityby means of their virulence, a term which refers to the degree ofpathogenicityof the microbe
Pathogenicity can be defined as the capacity of a microbe to cause damage in a host
Bacterial pathogens express a wide range of molecules that bind host cell targets to facilitate a variety of different host responses
A key to fighting bacterial disease is the identification and characterisation of all these different strategies
key strategies of pathogenicity
Capsule Cell wall Toxins Adhesins Invasion Intracellular living Regulation and response
key strategies of pathogenicity- capsule
Presence of capsule interferes with receptor mediated phagocytosis and distinguishes those that posses them as pathogenic strains
“Frustrated” phagocytosis
Those with a capsule can ‘escape’ this line of defence
Inhibits antibody binding
Direct inhibition of phagocytosis
Prevents capture by Neutrophil Extracellular Traps
Bacterial cell wall components bind to receptors on macrophages
Triggers release of cytokines
Activates coagulation pathway, complement pathway and additional proinflammatory signals
Excessive activation leads to damage to capillary endothelial cells
Reduced perfusion
Fever, hypotension, tissues destruction, acute respiratory distress, intravascular coagulation = multiple system organ failure (death)
key strategies of pathogenicity- toxins
exotoxins (produced inside gram positive bacteria) and endotoxins (produced as potion of cell wall in gram negative bacteria)
Proteins produced by pathogenic bacteria which are secreted into the surrounding medium or directly injected into host cells
These include:
A-B toxins
Proteolytic toxins
Pore forming toxins
Toxins – A-B toxins
Subunit A: enzymatic activity
Subunit B: binding and delivery
Enzyme activity varies but can include proteolysis (e.g. tetanus or botulinum)
Proteolytic toxins
Proteolysis results in inability of vesicles to fuse with nerve cell membrane and release neurotransmitter
Synpatobrevins are vesicle-associated membrane proteins
Membrane-disrupting toxins
Pore-forming toxins are produce by many pathogenic Gram negative pathogens
Act as virulence factors
Six distinct families of PFTs
Specificity determined by interactions with host cell
Structural modularity
bind to membrane and insert to form pore
key strategies of pathogenicity- Adhesins
Adhesion of pathogen to host surface
Includes:
Skin
Mucous membranes
Deeper tissues (lymphoid tissue; gastric and intestinal epithelia; alveolar lining; endothelial tissue
Needs to avoid mechanical ‘clearing’ forces
Adherence factors can be proteins or polysaccharides
Proteins:
Fimbrial (pili)
Afimbrial
Adherence factors can be proteins or polysaccharides
Polysaccharides:
Components of cell membrane, cell wall or capsule (e.g. teichoic acids; glucan, mannan)
Extracellular invasion:
Microbes produce enzymes that break down host tissues
Aids tissue invasion
Access to tissue niches for proliferation and dissemination
Microbe remains outside cells
Intracellular invasion:
Microbes penetrates cells of host
Survives within cells
Variety of cell targets
Some have obligate intracellular lifestyle (e.g. Chlamydia)
A means of survival & proliferation
Microbe actually penetrates cell of host tissue
Survives inside cell environment
Gram +ve, -ve and mycobacterial pathogenic species
Phagocytic and non-phagocytic cell types
Most bacteria use a type III secretion system to inject a chemical signal into their host cell
Activates host cell signalling pathway
Causes rearrangement of cell cytoskeleton so that bacteria is engulfed.
bacterial Intracellular living
Reactive oxygen intermediates
Lowering of pH of bacteria-containing vacuoles
Activation of degradative proteases
Inside an active phagolysosomal vacuole
Inside a vacuole that hasn’t fused with a lysosome
In host cell cytosol
Three strategies for exit from host cell:
Induced programmed cell (apoptosis)
Host cell destruction
Membrane-dependent exit
Biofilms
Biofilms can be defined as a microbially derived sessile community characterised by cells that are irreversibly attached to a surface or interface or to each other; are embedded in a matrix of extracellular polymeric substances that they have produced; and exhibit an altered phenotype with respect to growth rate and gene transcription Reduced penetration of antibiotic Neutralisation by certain bacterial enzymes Metabolic heterogeneity Oxygenation or pH gradients Persister cells Colony phenotype Antibiotic antagonism
Blood / Serum Sampling -Venepuncture sites
Jugular Cephalic Saphenous Medial Saphenous Lateral ear
describe the process of tackign a jugular sample
The vein israisedbycompressing it just dorsal to the thoracic inlet using thumb, ventral to the venepuncture site.
Insert needle at 45 degree angle
Pull back the plunger whilst still raising the vein until you reach the volume of blood you need.
Release your thumb before removing the needle.
Apply pressure
Blood / SerumSampling – Technique
Remove needle to transferblood sample.
Do not touch syringe inside tube due to additives altering results.
Invert sample as soon as possible.
Safely discard needle and syringeinto appropriate waste bin.
LABEL, LABEL, LABEL!
Check temperature needle for sample
Check time needed between collection and running sample
Correctly completesubmission forms
FNA Sampling
Investigates mass’s via inserting a needle into the masses
External
Internal
Lymph nodes
Quick, cost effective and relatively non-invasive procedure.
Can be done without the need of sedation/GA
Clipping and prepping is not always indicated, although clipping helpful to establish location and size.
Certainly,for internal aspirationsclipping and prepping is required
Wearing gloves, usedilutedchlorhexidine and fresh gauze swabsto clean the FNAlocation. Similar topreparing for a blood sample
Urine Sampling
Investigative procedure: Urinary tract infection (UTI) Kidney disease Diabetes Melitus Haematuria following certain medications
Obtaining a urine sample can either be via a free catch, catheterisation or cystocentesis.
Urine Sampling – Catheterisation technique FEMALE
Sedate patient if required
Position patient (easiest in sternal, legs hanging down from table
Clip any long hair around the vulva
Clean the vulva & surrounding area with dilute antiseptic solution. This will prevent nosocromial infection.
Flush the vulva vestibule with dilute antiseptic.
In a sterile manner open your sterile gloves, lubricant and catheter so as they are still lying on the sterile inner surface of the packaging.
.Put on gloves using open gloving technique.
8. Lubricate index finger which will be inserted into the vulva.
9. Insert index finger into vulva and feel for the pelvic brim.
10. Once at the pelvic brim, sweep side to side to feel the papilla (urethral opening)
11. Curl the finger slightly round and down behind it.
12. Using other hand, lubricate catheter tip and insert into vulva following your finger which is acting as a guide, once it has reached your fingertip, push it down and under the urethral opening, keeping your finger in place feed the catheter to the point whereyou visualised it should stop.
13. Urine should be flowing out of the catheter at this point attach a sterile syringe and aspirate the urine required.
14. Once finished collecting the urine, gently remove both finger and catheter and wipe away any excess lubricant or urine from around the vulva.
Urine Sampling – Catheterisation technique MALE
Gloves Antiseptic solution Gauze swabs Urinary catheter / tom cat catheter Lubricant Syringe
DOG & HORSES
Position lateral recumbency or standing (Horses)
Extrude the penis from the prepuce and wipe the urethral orifice,
Measure the approximate length of catheter (tip of penis to pelvic brim)
Lubricate the tip of the catheter with sterile jelly
Slide the catheter through the penile urethra the previously estimated length of the urethra.
Stop insertion when urine begins to fill the catheter or leaks from the end of the catheter.
Once you have entered the urinary bladder, release the penis into the prepuce.
CAT
Position dorsal or lateralrecumbency.
Sedation isgenerally required.
Extrude the penis byplacing gentle pressure on the prepucetowards the spine.
Gauze sponges may beused to aid in applying traction.
Lubricate a sterile catheter with sterilelubricating jelly and insert it into the penileurethra. 4.
Advance the catheter until urine isnoted in the catheter or is visible uponaspiration with a syringe.
Faecal Sampling technique
Gloves
Air-tight container
Sealable biohazard bag
Cool box for transportation of samples
Wear gloves.
Preferably collected from therectum where possible.
Animals such as lambs can be induced to defaecate by inserting a moistenedfinger into the rectum and massaging until the external sphincter relaxes.
For herd examination, collect different samples selected at random.
Poultry faecal samples cannot be taken from cloaca, there cage those to be sampled separately.
MUST be FRESH (within last 4-6hours)
For small animal, usingthe commercialspoon inside the faecal pot collectapprox. ½teaspoon into the faecal pot and close lid as soon as possible
Fill the container to capacity
Close the lid.
Important to exclude air to delay egg development.
Clearly label sample name,date and place of collection
Samples putin cool box for transportation.
Can refrigerateup to three weeks
DO NOT FREEZE.
Can use formalin if refrigeration is not possible, care as this is toxic and an irritant.
Follow health & safety regulations.
Skin Scrape Sampling – Technique
Gloves andapron.
Assistant
Surgical clippers
Sterile scalpel blade (size 10)
Liquid paraffin or 10% Potassium hydroxide (KOH).
Sterile container.
Pencil.
Microscope slides.
Bunsen burner (optional).
Wear PPE (Care of zoonosis)
Ask assistant to restrain patient
Select sample area
Lightly clip area if required – Care not to cause irritation or excoriation.
Squeeze a fold of skin between the thumb and forefinger.
Make several scrapings until petechial bleeding (capillary ooze) is present.
Add 1 drop of paraffin to a microscope slide and gently smear the sample.
Labelthe slide using a pencil.
The smear may be heated over a Bunsen flame in order to speed up the clearingprocess.
Cytology Samples -Technique
Otoscope
Cotton-tipped swabs
Microscope slides
Wear gloves
Use otoscope to determine location.
Holding cotton swab,gently insert the cotton swabs into the horizontal ear canal.
Roll the cotton swab several times.
Gently remove the swab from the ear canal.
Spread the cotton swab directly onto a microscopic slide until the specimen is evenly distributed.
Label slide
Put into microscope container.
Blood / Serum sampling technique
Needs a precise balance in order to function (Homeostasis)
These samples can tell us about;
Illness (e.g.IMHA - low red blood cell count)
Injury (e.g. internal perforation from stick injury – Low PCV)
Inflammation (e.g. wound – high white blood cell count)
Infection (e.g. bacteria seen in blood culture)
Medication thresholds (e.g. Hyperthroid – high T4)
Cleaning / Prep items
Sampling items
Containers
Paperwork
LOVELY assistant
Needle & Syringe
Various sizes of needles & syringes
Choose the appropriate size for the task
Your total blood volume will then tell you what size syringe youneed.
Barein mind the larger the syringe = increased risk of veincollapse
ALWAYScheck samples needed prior to collectingblood.
Needle size, you want to go as big as you can although consider thefollowing:
Patient’ssize
Venepuncturelocation.
Gauge needle, you may end up damaging the blood cells,which can affect results.
Horses typically18 gauge x 1 ½ inch needle and syringe dependant on amount of blood required.
Prepare ASEPTICALLY!
BloodTubes
Whattubes do you need for the test?
Refer tothe external pathology labprotocols or your own in-house protocols.
Are the tubes in date?
Total volume of blood you need = Amount of tubes.
Is it the right size tube?
Typical tubes often only require 0.5 or 1.3mL of blood.
Standard vacutainersgenerally need 2 or 4 mLs.
The tube size can be the same, but the volume needed candiffer.
Care not to cause trauma due to clipping as can introduce bacteria
Wear gloves
Prepare antiseptic at correct concentration
Wipe the clipped area from the venepuncture site outwards
Clipping helps visualise the vein
Antibiotic
A chemical substance produced by a micro-organism that inhibits bacteria e.g. penicillin
Bactericidal
kills bacteria
Bacteriostatic
prevents replication
antibiotic Time-dependent
length of time above MIC
antibiotic Concentration-dependent
– peak concentration
Antibiotics – modes of action
- Inhibition of bacterial cell wall synthesis
- Inhibition of bacterial protein synthesis
- Injury to the bacterial cell membrane
- Inhibition of either DNA or RNA synthesis in the bacterium
antibiotic resistance- Reduced uptake
Decreased uptake
Efflux
Enzymatic modification
Enzymatic degradation
Altered penicillin binding proteins (PBPs)
Altered target
Target overproduction
antibiotic resistance- Reduced uptake
Reduced outer membrane (OM) permeability results in reduced uptake of antibiotics
antibiotic resistance- Increased efflux
Single or multi-component pumps Found in Gram +ve and Gram –ve Antibiotics (except polymyxins) susceptible to efflux systems Most are multi-drug transporters Increased gene expression = more pumps
antibiotic resistance-Enzymatic deactivation
Aminoglycosides-modifying enzymes act as acetyltransferase, nucleotidyltransferase, or phosphotransferase enzymes
Chloramphenicol acetyltransferase catalyses the acetylation of chloramphenicol and the resulting product does not bind to bacterial ribosomes
antibiotic resistance- Modification of target
Interaction between antibiotic and target is very specific
Mutations in penicillin binding proteins (PBPs) e.g. transpeptidase reduce affinity to β-lactam antibiotics
Change in target site
Spontaneous mutation or transposon-mediated
Mutations in RNA polymerase (rifamycins)
Mutations in DNA gyrase (quinolones)
antibiotic resistance-
Target overproduction
Antimetabolite antibiotics can be counteracted by overproduction of the relevant enzyme or bypassing the metabolic pathway
Johne’s disease
Granulomatous enteritis of ruminant animals
Granulomas: form when immune system attempts to wall off foreign substances results in thickening of intestine, inhibits nutrient absorption
Caused by Mycobacterium avium ssp. paratuberculosis
Initial signs of MAP infection are subtle:
Decreased milk production, reduced BCS, low fertility, roughening of the hair coat
Clinical characteristics
Loose manure
Weight loss
Chronic & Progressive
No cure dehydration, cachexia, death
Causative bacteria found on ~70% of U.S. dairy farms
UK prevalence data are limited, but bacteria likely on >50% of UK dairy farms
Mycobacterial infections
E.g., Tuberculosis, Leprosy
Slow-growing, resilient
Resistant to acids, alkalis, and detergents
Confirmed by acid-fast (Ziehl Neelsen) stain
Pathogenesis & Immunology of MAP infections
When MAP reaches the ileum it is transported through the cells covering the Peyer’s patches and is taken up by macrophages in the stroma
Leads to excessive expression of IL-10 and decreased expression of MHC molecules
Instead of being destroyed by the macrophages, MAP proliferates within them
When macrophages rupture, MAP is released into neighboring tissue and taken up by other macrophages
Initially a Th1-type immune response predominates, then a Th2-type response
Th2 regulatory cytokines are involved in triggering the humoral immune response
During this shift, cows shed MAP in increasing amounts. Infection spreads to other tissues
Leads to excessive expression of IL-10 and decreased expression of MHC molecules
Instead of being destroyed by the macrophages, MAP proliferates within them
When macrophages rupture, MAP is released into neighboring tissue and taken up by other macrophages
Granulomas form when the immune system responds by recruiting additional monocytes and lymphocytes (types of white blood cells)
These cells fuse together into multinucleated giant cells and epithelioid cells
Results in visible thickening of intestinal mucosa, which inhibits nutrient absorption and leads to clinical symptoms of the disease
Diagnostic tests for MAP
Main types: ELISA, PCR, Culture
– ELISA detects MAP antibodies, PCR and culture detect causal organism
– Diagnostic matrices for ante-mortem testing are serum, milk, or fecal samples
Post-mortem diagnoses are typically obtained via bacterial culture of tissues from intestinal regions such as the ilium, ileocecal junction, ileocecal lymph nodes, or mesenteric lymph nodes
Culture: costly, takes 16 weeks, lacks sensitivity (MAP is fastidious– requires mycobactin J, a siderophore for growth)
ELISA: lacks sensitivity (no antibody production in early infection stages)
PCR: some of the targets aren’t specific to MAP, found in other mycobacterial species, can be bad at differentiating between live and dead bacteria
On-farm control measures of jhones disease
Management of the calving area
Hygiene of partiparturient animals (Ansari-Lari et al., 2009)
Individual calving areas (not doubling as sick pens or shared with other lactating cows; Pithua et al., 2011)
Colostrum/milk management
Avoid raw pooled colostrum (Nielsen et al., 2008) or feed milk replacer (Muskens et al., 2003)
Pasture management
Spreading manure linked to higher infection risk (Obasanjo et al., 1997)
Avoid sharing pasture between adults and heifers (Marce et al., 2011)
Implement a test and cull program , source replacement animals from a single negative herd (Orpin et al., 2005)
