VNSA5 Flashcards
What is a parasite?
Eukaryotic, complex structures contained within membrane, has a nucleus, single celled or multi cellular.
Define ectoparasites
Parasites living on or burrowing into hosts skin or coat
What are ectoparasites apart of?
Phylum arthropoda
Includes invertebrate insects, spiders and crustaceans
What do ectoparasites look like ?
Segmented bodies and either a tough protective, semi-transparent substance or an exoskeleton (rigid external covering for the body/skeleton)
Jointed limbs
Describe insects
Adults:
3 body parts - head, thorax and abdomen
3 pairs of legs
Eg - Lice, fleas and dipteran flies
Describe arachnids
-All have 2 body parts: cephalothorax (fused head and thorax) and abdomen
-adult and nymph (immature, before adulthood) stages
-adult and nymph have 8 pairs of legs
-juvenile stages (larvae) have 6 pairs of legs
-eg. mites and ticks
What are fleas ?
-blood sucking insects, wingless and dark brown
-laterally flattened to move between hairs
-robust back legs for jumping
-approx 3mm long
-mouthparts are adapted to pierce skin and suck blood
-saliva is injected which contains antigens that encourage an allergic response.
-flea allergic dermatitis (FAD)
What is a ctenocephalides felis?
A cat flea
Most common on cats dogs and rabbits
Hairy moustache and mullet/combs
What is a ctenocephalides canis ?
A dog flea
Most common in dogs in permanent kennels
Less hairy
1-2.5mm long
What is a archaeopsylla erinacei?
A hedgehog flea
Elongated
What is a spillopsyllus cuniculi?
A wild rabbit flea
Hair beard and mullet
Flea life cycle
Flea eggs - lay eggs after a blood meal, eggs drop off into environment
Flea larvae - hatch out of eggs when conditions are warm and humid
Flea pupae - larvae spin into a cocoon and develop into pupae (1-2 wks)
Adult fleas - hatch from cocoon and continue to infest pet
What can fleas cause ?
Pruritis - flea allergic dermatitis
What is an infestation of lice called ?
Pediculosis
Describe lice
-small and wingless
-dorso ventrally flattened
-approx 2mm long
-adults complete life cycle on the host
-can affect = cats dogs horses rabbits rodents and birds but host specific
-transmission is easy, close contact/fomites
-large numbers cause irritation to animals
Sucking louse - linognathus setosus
-affects dogs
-worldwide
-1.5 to 2.5 mm long
-often found on heads (eyes, ears) but also neck and chest
-elongated narrow heads
-piercing mouthparts
-feed on blood
-large numbers can cause infestation
-fipronil is a broad spectrum insecticide
Chewing/biting louse - Felicola substratus
-cats worldwide
-chewing louse
-transmits dipylidium caninum
-they have shorter broader heads and feed on skin debris
Chewing/biting louse - trichodectes canis
-dogs worldwide
-chewing louse
-intermediate host for dipylidium caninum
-prefers head, neck and back
-they have shorter broader heads and feed on skin debris
Life cycle of the louse
Eggs
First stage larva
Second stage larva
Third stage larva
Adult
Diagnosis and treatment of lice
Visualisation of eggs or lice (skin scrapes or brushings may be needed)
Cleaning the environment inc fomites
Treatment - insecticidal wash/spray/spot on
What are dipteran flies?
Blue and green bottle flies
Blow flies
Botfly
What is myiasis
Aka fly strike
Invasion of living tissue by dipteran fly larvae
Risk is increased in the summer - especially if animal is soiled due to smelly moist area
Diagnosis and treatment of myiasis
-depressed and restless
-may not eat
-full examination
-maggots easily visible
-all larvae needs to be removed
-skin bathed with mild antiseptic
-topical treatment may be sufficient
What disease can sandflies transmit ?
Leishmaniasis
-skin mouth and nasal ulcers
-anaemia, fever, enlarged spleen and liver
-zoonotic
What can mosquitos carry?
Heartworm - resides in right side of heart.
What category are ticks in ?
Arachnids
What is the name of the specialised mouth part ticks have?
Hypostome. Developed for piercing skin to gain their blood meal
What is an ixodes ricinus
Sheep tick - seen in rural areas (moors and woodlands)
What is an ixodes hexagonus?
Hedgehog tick - seen in urban areas (parks and gardens)
What is an ixodes canisuga?
Only affects dogs and cats so may be a problem if boarding in kennels
Lifecycle of a tick
Adult female feeds on host, becomes engorged and drops off
Engorged female lays eggs and dies
Eggs hatch into larvae and attach to a host
Engorged larvae detach from host and molt into lymph’s
Nymphs attach and feed of a larger host
Engorged nymphs detach from host and molt into adults
How many legs does a larval tick have ?
Three
How many legs does the nymphal tick have?
4
Diagnosis and treatment for ticks
Visually seen
Need a tick remover
Treatments - simparica, bravecto, frontline
What are mites?
Most are permanent ectoparasites
Exception = Dermanyssus gallinae (red mite of poultry) and trombicula autumnalis (harvest mite) only the larva is parasitic
What is the transmission of mites caused by ?
Direct contact
How do you diagnose mites ?
-hair plucks
-hair brushings
-tape impressions
-skin scrapings
Otodectes cynotis - ear mite
Surface mite - seen on dog, cat, ferret
-long legs, unjointed pedicles
-apodeme unjointed
-0.4mm long
-live in ear canal causing otitis externa and dark brown waxy discharge
-highly contagious
-small white moving dots
Life cycle of an ear mite
Adults live in ear canal and brouse on wax and debris
Eggs hatch
Larvae feed for 4-5 days before moulting
Nymph feeds for 4 days molts and feeds for 4 more days before moulting to adult
Lifespan is spent on 1 host
Clinical signs, diagnosis and treatment for ear mites
-head scratching
-scratching
-rubbing ears
-trauma and haematoma to pinna
-Cleaning ears, followed with an acaricide (3 weeks)
-antibiotic may be indicated
-contact animals should be treated (stronghold/advocate)
Cheyletiella spp. surface mite
Walking dandruff
0.4-5mm long (just visible to the naked eye)
8 legs with combs not claws
Palpi (hook like mouth parts)
Poss zoonotic (may bite but dont survive long = raised spots and pruritis)
Direct contact
Affects dogs cats and rabbits
Cheyletiella spp. life cycle
Adult females lay eggs one by one on the host coat
Eggs are attached to the hairs
Eggs hatch into larvae after approx 4 days
Larvae moults into nymphs and in 9-10 days develop into adults
Infection occurs by direct host to host contact
Diagnosis and Treatment of Cheyletiella spp.
By examination - coat brushings or tape strips for adults or eggs
Disinfection of area as can survive for some days in environment
Araricides: ivermectin, pyrethrin topical products
Trombicula autumnalis - harvest mite
Only larval stages are parasitic
Late summer/early autumn
Orange/red colour
3 pairs of legs
Intense irritation caused
Seen on feet and ears
Treat with ectoparasite spray
Life cycle of a harvest mite
Eggs
Larva
Nymph
Adult
What do burrowing/subsurface mites do ?
Create tunnels within the surface layers of skin
Lay their eggs within small pockets
All have short legs
4 burrowing mites seen in pets
Sarcoptes scabei var. canis
Highly contagious and zoonotic
Affects dogs, occasionally cats and horses
Transmission = close contact (can survive in environment like bedding)
Short stubby legs
Pedicles with suckers
Y shaped apodeme at its neck
0.4mm long
Life cycle:
Females burrow into the skin and lay eggs in the burrows
Eggs hatch and the mites move, make burrows of their own and process repeats itself
Diagnosis and treatment of sarcoptes scabei var. canis
Deep skin scrape (hard to always find the mites)
Blood test (antibodies/immune response)
Medicated baths and dips
Injections and oral meds
Many animals require a combination to resolve the issue
Trixaxarus caviae - burrowing mite
Seen in Guinea pigs
Intense pruritis - can cause seizures
Severe self trauma
Reddening of the skin/swelling
Abnormal area of thickened skin
Chronic infestation = alopecia
Notoedres spp. - burrowing mite
Transmission by close contact
Mites or eggs can survive in environment for several days
Affecting cats (and rats)
0.36mm long
Presents much like sarcoptes scabi spp
Rare in uk
Test by skin scrapes
Demodex spp. burrowing mite
Normal cutaneous flora
If immunocompromised mite overgrowth can occur
Not typical appearance
Cigar shaped with short stubby legs
0.2mm long
Host specific
Life cycle:
Adult
Ovum
Larva
Protonymph
Nymph
Clinical signs and treatment of demodex spp.
Non pruritic alopecia
Localised demodicosis
Generalised demodicosis
Advocate ( weekly application not monthly and then re skin scrape) can be a lengthy process.
Aludex- think COSHH flammable and toxic (ventilation and PPE)
Name the 4 burrowing/subsurface mites
-sarcoptes scabei var. canis
-notodres spp.
-demodex spp.
-tricacarus caviae
What are the 4 types of fleas?
Ctenocephalides felis - cat flea
Ctenocephalides Canis - dog flea
Archaeopsylla erinacei - hedgehog flea
Spillopsyllus cuniculi - wild rabbit flea
Name the sucking louce
Linognathus setosus
Name the chewing/biting louce
Felicola substratus
Trichodectes Canis
Name the tick species seen in the UK
Ixodes ricinus
Ixodes hexagonus
Ixodes canisuga
Name the surface mites
Otodectes cynotis
Trombicula autumnalis
Psoroptes spp.
Cheyletiella spp.
Name the disease producing infectious agents
Viruses
Bacteria
Fungi
Protozoa
Prions
What do the following units stand for?
Km , m , mm , um, nm
Km - Kilometer
M - meter
Mm - millimetre
Um- micrometer
Nm - Nanometer
What is a prokaryotic cell
Bacteria and archaea
What is a eukaryotic cell
Fungi and animals
When an interaction with the host is harmful what is it called?
Disease causing microorganisms
Define commensal organisms
Having no effect on the host
Define gut microflora
Benefit to the host
Define heterotrophic
Use organic carbon from other organisms for their own growth
Define autotrophic
They produce their own food from simpler molecules
Define saprophytic
They live off dead or decaying matter
Define parasitic
Live in or on a living organism at the hosts expense
Define mutualism
The host and microorganism benefits from the relationship (microflora gut bacteria)
Define contamination
Exposure of host/tissue to microorganisms
Not infection until the microorganisms have colonised the host
Define colonisation
Microorganisms multiples within a host — leading to infection
Define infection
Microorganism has colonised the host and clinical signs are seen
Infections causing harm to the host are pathogenic
Define contagion
Spread of infectious diseases from one host to another
Direct and Indirect
Therefore the disease is contagious
Structure of viruses
Extremely small -> 20-300nm
Each viral particle (viron) has 2 components:
Nucleic acid core and protein coat
Some viruses also have an outer envelope, often formed by the hosts cell membrane.
Not always recognised as living organisms as unable to reproduce without a host cell (obligate parasites)
They are reliant on the host cell to provide necessary nutrition for survival
What are the 4 shapes of a nucleocapsid (virus)
Helical - Spiral shape
Icosahedral - 2- triangular faces
Complex - combination of 2 other shapes
Composite - separate elements
Viral replication
- viruses can only attach to cells with compatible receptors
-tissue tropism
-they only infect certain species
-replication takes place in the hosts cells
How does a virus enter the cell
-attaches and enters a suitable cell
(Enveloped viruses fuse with the host membrane, releasing nucleocapsod into the cell)
(Non-enveloped viruses induce the host cell to engulf it)
-capsid breaks down to release viral nucleic acid
-it replicates by controlling the cells normal metabolism
-the cell produces the necessary components of new viral particles
-these are then assembled and released from the cell
-if the virus is naked the host cell normally ruptures and destroys the cell membrane
-if the virus is enveloped it leaves the cell membrane, removing some to form the viral envelope
Define adsorption
(Virus)
Virus attaches to the host cell
Define penetration
(Virus)
Injects its genome into the host cell
Define viral genome replication
Viral genome replicates using the hosts cellular machinery
Define assembly
(Virus)
Viral components assessable and viruses fully develop
Define maturation
(Virus)
Viral components assemble and viruses fully develop
Define release
(Virus )
Newly produced viruses are expelled from the host cell
Define direct transmission
Cat licking nasal secretions from another infected with calcivirus
Define indirect transmission
Dog licking the floor of a kennel, previously used by a dog suffering with parvovirus
How do you diagnose a viral infection?
-history taken
-clinical signs
-symptoms of viral infections may be similar so further identification is required:
-electron microscopy is possible with light if clumped
-serology - detection of specific antibody production in response to the virus
- PCR (polymerase chain reaction) amplifies quantities of DNA from the virus
Treatment for viral infections
-supportive care
-fluids
-nutrition
-pain relief
-antiviral drugs (used more in humans)
Prevention of viral infections
-border controls
-accommodation design
-disinfectants effective against viruses
-vaccination
What are the types of bacteria
Bacilli - cylindrical or rods
Vibrios - curved bacilli.
Cocci - spherical
Spirochaetes - spiral or helical
Define diplococci bacteria
Can exist singly while others remain in pairs following cell division
Define streptococci bacteria
Those that remain attached in chains
Define staphylococci bacteria
Divide randomly and from irregular grape like clusters
Why is it so important to be able to identify bacteria ?
To ensure that the correct antibacterial treatment is used.
Explain gram staining
Allows you to see whether it’s Gram+ or Gram-
Be able to see the structure and shape of bacteria
Knowing where the sample was taken from you may be able to identify the bacteria well enough to start treatment.
What colour is gram+ bacteria
Remain purple as they resist the decolouration
What colour is gram-
Will appear pink.
Due to the Fuchsin application together with the other material on the slide
Define a cell wall
Bacteria
Rigid stricture
Mainly made of peptidoglycan
Maintains cell shape and prevents bursting, varies in thickness
Define cell membrane
Bacteria
Lies just inside the cell wall.
Selectively permeable
Controls passage of substances in and out of the
Define cytoplasm
Bacteria
A thick fluid containing dissolved substances such as nutrients, waste products and enzymes
Define plasmid
bacteria
Extra piece of DNA
Can replicate independently from the DNA
Define mesosome
Bacteria
Infolding of the cell membrane
Site of cell respiration
Provides a larger surface area
Define flagellum
Bacteria
Provides movement
Long hollow tubes of a contractile protein
Define bacteria chromosome
Bacteria
Suspended within the cytoplasm
Extensively coiled molecule containing DNA
Define ribosomes
Bacteria
Contain ribonucleic acid (RNA)
Site of protein synthesis
Define what a capsule and slime layer is
Bacteria
Gelatinous capsule
Vary in thickness
Act as a barrier between the bacterium and its environment
Bacteria reproduction
Binary fission - asexual - 2 genetically identical cells from a single mature cell
Or
Gene transfer
Explain gene transfer
Bacteria reproduction
Transformation - a recipient cell takes up DNA from the environment
Transduction - transfer of DNA from one cell to another via a replicating virus
Conjunction - transfer of genes from a donor to a recipient between 2 temporarily connected cells.
The donor bacterium extends a rod like sex pilus that connects with the recipient bacteria
The donor cell is not killed (like transformation and transduction)
What do bacteria need to grow?
-supply of suitable nutrients
-correct temp (37 degrees in mammalian bodies)
-correct pH (7-7.4 in mammals)
-water
-correct gaseous environment
Endospores
Some bacteria produce dominant spores
Highly resistant to adverse environmental conditions
Endospores are formed when the bacteria are deprived of a vital factor of life
Formation of endospores by sporulation
-one bacterial vegetive cell
Unfavourable conditions
-endospore formed
Germination
-one bacterial vegetive cell
Spore formation is not reproduction
How can you kill bacterial spores?
-autoclaving (moist heat, 121 degrees under pressure 6.9kPa > 15 mins)
-tyndallisation
-dry heat (160 degrees at least 2 hours)
What are toxins ?
Poisonous substances produced by bacteria
Effects can be - local to infection, systemic
Two forms of toxin are: exotoxins and endotoxins
Exotoxins
-Excreted by the cell
-released mainly by Gram+ve bacteria during metabolism
-enter surrounding tissues or systemic circulation
-very potent
-lethal in small quantities
-can enter into food = food poisoning
-can be destroyed by heat and some chemicals
-body produces antibodies in response to exotoxins —> antitoxins
Endotoxins
-inside the cell
- Gram-ve bacteria release endotoxins as the cell disintegrates and dies
-less toxic
-resistent to heat
-cannot create a toxoid to them
-after surgery in horses or GDV
-once in the circulation they cause a number of non-specific problems
-pyrexia
-in large concentrations they cause serious reduction in blood pressure
-endotoxic shock
Diseases caused by bacteria
Clinical symptoms can be caused by:
-presence of bacterium
-damage to the localised tissue from the inflammatory reaction induced by the bacteria
-toxins produced by the bacteria
Diagnosis of bacteria
-perform a full clinical examination
-take a full history
-identification of the causal bacteria by smears and cultures (diagnostics)
Treatments of bacteria
Depends on - bacteria involved and infection location
-topical/systemic antibacterial
-broad/narrow spectrum
-important to consider tissue penetration (will it get to infection site)
-some have a destructive effect on the normal gut microflora
When should antibacterial drugs be used?
For a minimum length of time as necessary to be effective
Use an appropriate drug with a narrow spectrum if possible
Otherwise body can become resistance to antibacterial drugs
Diagnosis of fungi
- can be hard as found asymptomatically on normal skin
- dermatophytes
-microscopic examination of hair plucks
-some species fluoresce under woods lamps
-cultured on specialist media
Treatment of fungi
-often treated topically alone
-fungicidal washes
-repeated regularly over prolonged periods of time
- eg. Malaseb - chlorhexidine and miconazole
-systemic treatments are sometimes indicated
Protozoa
-single celled organism
-many are motile
-10-200um
-free living in the environment
-parasitic once within the body
-infection can be asymptomatic or cause clinical signs
-disease more commonly seen in young or debilitated patients
-severity of symptoms vary
-protozoan life cycles are complex
-most replicate asexually (binary fission)
-some also reproduce sexually by gametogony - only in a definitive host
Oocycst
Have a protective membrane or thickened wall
Survive for long periods of time in the environment
Passed in faeces
Bradyzoites
Found in the body tissues awaiting ingestion of the tissue by another
Host eaten by definitive host
Tachyzoites
Rapidly multiplying, causing tissue destruction and spreading of infection
Diagnosis of protozoan infection
Many are difficult to detect
Shedding of infective forms can be intermittent
-diagnosis normally by identification of oocysts in faeces
-serology
-signs of toxoplasma
Prevention of protozoan infection
-vaccinate sheep against toxoplasma Gondi
-handwashing
-prevent cats from accessing sheep food stores
-Pregnant women; not clean litter trays, wear gloves whilst gardening, not assist with lambing ewes
-ensure meat is cooked properly
Prions
-smallest infectious particle
-protein particles, contain no genetic material
-cannot self replicate
-reliant on host organism
-they alter normal protein production, producing more prions
-cause neurodegenerative disease resulting in death
-usually have a very long incubation period (2 months - 2 years)
-transmission is by ingestion of infected tissue/fluids
-thought to remain viable in the soil for some time
(Eg mad cow disease)
Diagnosis and prevention of prions
Diagnosis - clinical signs on animal, lymph node samples in live animals and appearance of brain tissue post mortem
Prevention - slaughter, removal of bovine offal from food chain, ban on feeding processed animal protein
Fungi
Only infects a few animals
Grow - aerobically
Unicellular or multicellular
Membrane bound nucleus
Nucleic acid - DNA and RNA
Absorbs nutrients from the surface they grow on (saprophytic or parasitic)
2 groups - moulds and yeasts
Moulds
-multicellular structure
-hard capsule to protect DNA inside
-made up of long filamenets - hyphae
-reproduce sexually but more commonly asexually
-spores spread via airborne methods and fomites
Yeasts
-require a constant food source
-unicellular
-usually commensal - become pathogenic under certain conditions
-reproduce by budding
What can endoparasites be divided into?
-helminths
-Protozoa
What are Protozoal parasites ?
Small unicellular organisms
What 3 categories can helminths be split into?
-trematodes (flukes)
-cestodes (tapeworm)
-nematodes (roundworms)
Cestodes - tapeworm
Tape like appearance with no digestive tract. It is composed of 3 main parts (head neck and strobila)
What is the scolex
(Cestodes - tapeworm)
-head
-either in larva or adult stage
-has hooks and suckers
-animal is attached to tissues of its host
What is the rostellum
(Cestodes, tapeworm)
-anterior part of the scolex
-Cone like structure
-some species have retractable hooks
What is the strobila
(Cestodes, tapeworm)
-The segmented part
-contain both male and female reproductive organs
-absorb nutrients from the gut contents of the host
What is the proglottid
(Cestodes, tapeworm)
-small segments - size of a grain of rice
-these segments break off and pass into the stool
-individual segments that make up the strobilla
Are tapeworms hermaphrodites ?
Yes
They have both male and female reproductive organs in each proglottid.
As the proglottid matures, reproduction takes place and eggs develop within it.
When fully mature it is an egg - containing structure
What is the immature stage of a cestode called ?
Metacestode
It develops into the intermediate host, it is here there is often a problem not the final host.
Define cysticercus
(Metacestodes)
Fluid filled cyst
Containing a scolex which is inverted into a sac.
Muscle tissue of host
Define cysticeroid
(Metacestode)
A single scolex
(Invertebrate intermediate hosts)
Define coenurus
(Metacestode)
Cyst with multiple attached scolices
Define hydatid cyst
(Metacestode)
Large cyst containing many scolices
Dipylidium caninum
Tapeworms
-most common tapeworm seen in the UK
-affects dogs and cats
-can be zoonotic
-intermediate hosts = fleas and biting lice in dogs
-the cysticeroid develops in the flea, is eaten and released into the small intestine of host where scolex attaches to the GI wall
-normally diagnosed by presence of motile segments containing egg packets around the anus or in faeces.
Echinococcus granulosus
-affects dogs
-often asymptomatic
-intermediate host = sheep
-zoonotic and humans can act as an intermediate host (cysts develop in liver and lungs)
-hard to control infection in the intermediate host, better to control in the final host.
(Prevention = hygiene and not letting dogs of in a sheep field as dead carcass can be ingested)
Taenia spp.
tapeworm
-seen in both dogs and cats
-zoonotic
-infected by; intermediate hosts ingesting eggs from the ground
-metacestode cyst developing (cysticercus)
-ingestion of raw meat or offal infected with taenia spp.
Infection control = preventing final hosts accessing uncooked flesh
What are the hosts of taenia tapeworms
T. Taeniaeformis - cat - immediate host = rat or mouse
T. Serialis - dog - immediate host = rabbit
T. Pisiformis - dog - immediate host = rabbit
T. Ovis - dog - immediate host = sheep
T. Hydatigena - dog - immediate host = sheep/cattle/pig
T.multiceps - dog - immediate host = sheep/cattle
What are nematodes ?
Worms
They live inside and feed off an animals intestines after being swallowed - can be found in faeces and vomit
They’re round in cross section, have cylindrical bodies and resemble spaghetti.
They’re light brown and a few inches long
They have an alimentary tract
Most have a direct lifecycle (excluding some lungworm) and others have paratenic/intermediate hosts (slug/snail)
Name the type of nematodes
-ascarids
-hookworm
-whipworm
-bladder worm
-lungworm
What are ascarids ?
Large fleshy worms
More of a problem to young puppies and kittens
Most common group in veterinary practices
-toxocara canis
-toxocara leonina
-toxocara cacti
Toxocara Canis
Nematode - ascarid (roundworm)
-can affect dogs, cats and foxes
-lives in the intestines
-infection can occur by; ingesting them from the environment, in utero from day 42, via the dams milk
-causes puppies to have distended bellies, and can cause vomiting and diarrhoea, severe infestations can cause intestinal blockage
-as immunity develops they are expelled spontaneously from about 7weeks of age, being free of them by 6-7months of age
-zoonotic
Toxocara Cati
Affects cats - young kittens
Transfer the same as T.canis but unable to pass through the placenta
Worms have ‘wings’ on their heads
Potential to be zoonotic
Infection occurs:
-via queens milk (infection is patent for around 6 weeks)
-from the environment
-can cause stunted growth and pot bellied appearance
Toxascaris leonina
-Affects dogs and cats
-no infection in utero or via milk
-infection caused by ingestion or paratenic host
-usually well tolerated with minimal clinical signs of infection
-rarely zoonotic
Give 2 examples of hookworms
-uncinaria stenocephala
-ancylostoma caninum
Uncinaria stenocephala
-Seen in dogs (rarely affects cats)
-known as the northern hookworm
-seen in greyhounds and hunt kennels
-infestation caused by ingesting larvae from the environment
-dogs can also become infected by eating a host (small mammals) containing infective larvae
-attaches to intestinal mucosa by its mouth parts, inflicting damage by feeding off tissue fluid
-larvae can penetrate the skin and cause infection (skin and foot)
- symptoms: diarrhoea, anaemia, anorexic and lethargy - severe infestations cause the animal to look malnourished.
Trichuris Vulpis
Whipworm
-affects dogs
-present in large intestines, feed on blood and tissue fluid by damaging the intestinal lining
-whip like appearance
-wide posterior end free in the intestinal lumen
-narrow anterior end buried in the mucosa
-in large numbers cause bloody diarrhoea, but normaly asymptomatic
-characteristic eggs that are very resistant due to thick wall (survive long periods on the ground)
Dirofilaria immitis
Heartworm
-not in the UK yet
-adults live in the heart
-immature stages (microfilariae) circulate the blood
-transmission: via mosquito
Severe infection can cause right sided heart failure (RHS)
-symptoms present as: lethargy, breathing difficulties, hypertension, heart failure
Capilaria plica
Bladder worms
-seen in dogs but rare in the UK
-adults live in the bladder and are passed in urine
-similar to trichuris vulpis
-rarely a problem
Name the type of Lungworms
-aelurostrongylus abstrusus - cats
-angiostrongylus vasorum - dogs
-oslerus osleri-dogs
Aelurostrongylus abstrusus
Lungworm in cats
-infected by ingestion of intermediate host (slug or snail)
-adult worm lives in lung tissue (may cause coughing)
-larvae is coughed up and swallowed and passed in faeces
Angiostrongylus vasorum
Lungworm in dogs
-infection by eating a slug or snail containing infective larvae or eating larvae off the ground
-adults live in the pulmonary artery and can be fatal
-eggs passed into lung alveoli and hatch
-eggs are coughed up and swallowed and passes in faeces
Oslerus osleri
Lungworm in dogs
-live in small nodules at the tracheal bifurcation in dogs
-adults produce larvae which are then coughed up and swallowed
-life cycle is direct - there is no intermediate host
How are roundworms treated ?
-fenbendazole (panacur)
-milbemycin (milbemax, nexguard)
-piperazine (prazitel, endoguard)
-pyrantel (drontal)
Define disinfection
A process that eliminates many or all pathogenic microorganisms, except bacterial spores or inanimate objects
Define sterilisation
The process of making something free from bacteria or other living microorganisms
Define antisepsis
The destruction or inhibition of microorganisms on living tissues, limiting or preventing infection
Define asepsis
A condition in which no living disease causing microorganisms are present
Define disinfectant
A chemical that destroys, inactivates or reduces the concentration of pathogens
Define nosocomial infections
Infection acquired whilst receiving care at the practice
Define cleaning
The act of removing dirt or something undesirable
What is a clinical audit and why do have them?
A quality improvement process that seeks to improve patient care and outcomes through systematic review of care against explicit criteria and the implementation of change.
We have them to improve standards of care, as a part of PSS and to improve in house protocols or develop them.
What is thermocouple testing ?
A sensor used to measure temperature
Heat sensitive tips are placed in the sterilising chamber and connected to a temperature recording device, monitoring it throughout the cycle
Should be completed annually. Checks that effective sterilisation is happening.
Sterilisation indicators
External - used every time and shows exposure to sterilisation (on the bag itself)
Internal - placed within the pack, used especially if large and bulky (TST strips)
What types of sterilisation indicators are used?
Browne’s tubes - not often used anymore - glass tubes containing liquid which change colour
Bowie dick tape - beige tape with chemical strips change colour when exposed to a temp of 121 degrees
Sterilisation pouches - has an indicator on the pouch that changes colour
Chemical indicator strips (TST) - placed inside the pouch and changes colour
Spore testing strip - strips with dried bacterial spores inside placed within the load. No growth means sterilisation was effective. Have to be placed onto culture medium + incubated for 72 hours.
Ethylene oxide dosemeter strips - thin tube containing material that changes from yellow to blue after EO exposure time.
Ethylene oxide indicator stickers - stuck on outside of pack. Yellow dot that changes to blue after prolonged exposure to EO. Can change colour after being exposed to daylight so store in darkness
Define antimicrobial
Destroying or inhibiting the growth of microorganisms and especially pathogenic microorganisms
Define antibacterial
Prevents the growth or spread of bacteria
Define antibiotic
A drug
Natural products of microbial metabolism which kill or inhibit the growth of other micro-organisms
Define what a bactericidal antibiotic is
Antibiotic agents that kill bacterial organisms
Define bacteriostatic
The agent that prevents the growth of bacteria
Define the action ‘inhibition of the cell wall’
Prevents bacteria cell wall forming correctly
Define the action ‘disruption of microbial cell membrane’
Change membrane permeability
Affects transport in and out of
Define the action ‘inhibition of protein synthesis’
Affect protein synthesis in ribosomes or nucleus preventing effective replication
Define the action ‘interference with metabolic process’
Interfere with or inhibit folic acid production
What is antibiotic resistance?
Resistance of bacteria to certain antibiotics or antimicrobials
It can come from natural resistance, acquired resistance (natural) mutation or acquisition of new genes
What are antimicrobial agents ?
Synthetic antimicrobials that are manufactured not natural
What is a superbug ?
A bacterium that has resistance to more than 1 antibiotic/antimicrobial
What do we need to consider when using antibacterials?
Spectrum of activity
Site of infection
Host factors
Side effects
Potential drug interactions
Should only be used when absolutely necessary
Antibiotic overuse
The more they are used the greater chance of bacteria developing resistant genes and these being passed on.
This can make bacteria becoming resistant to one or more antibiotics
Not finishing courses of antibiotics means the infection may not be cleared up and allows the possibility of further infections and infiltration of resistant genes making the same agent ineffective
How can we minimise the risk of antibiotic resistance?
-more culture and sensitivity testing
-using the right agent the first time around - eliminating infection before they can mutate
-complete the course
-only use if necessary
What is MRSA and how is it transmitted?
Methicillin resistant staphylococcus aureus
It is a bacteria (commensal)
Staph infection
Zoonotic
Nosocomial infection
Transmitted by contact with infected animals or fomites
It can live harmlessly on the skin
In a study 7-13% of nurses and vets were colonised with MRSA
Acquired directly or indirectly through veterinary premises
It can be prevented through good hygiene, PPE and cleaning
What is C-Difficlile and how is it prevented
-clostridium difficile
Causes diarrhoea (GI upset)
Strains resistant to clindamycin and fluoroquinolones
Zoonotic
GI infections
E-coli and salmonella
Prevented through good infection control, hand hygiene, limit public access to hospital wards, correct disinfection use, clean everywhere
Define contamination
Exposure of a host or tissue to microorganisms
Not infection until the microorganisms have colonised the host
Define colonisation
Microorganism multiplies within a host - leading to infection
Define infection
Microorganism has ‘colonised’ the host and is multiplying in numbers
Causing clinical signs
Infections causing harm to the host are ‘pathogenic’
What is a disease?
A state in which normal functions are disturbed or altered at cellular, tissue, organ or whole organism level
What is a disorder?
An illness that disrupts normal physical or mental functions
What is an infectious disease?
An illness caused by harmful agents (pathogens) that get into your body
What is a non-infectious disease
Diseases that are not spread through infection or through people, but are typically caused by unhealthy behaviours
What is a contagious disease?
A disease that can spread rapidly from person to person through direct contact, indirect contact or droplet contact (inc parasites)
What is a pathogen
Any disease producing agent or microorganism
To produce disease an infectious organism must overcome the animals external and internal defence mechanisms
In order to trigger disease pathogens need to;
-penetrate host defences and establish themselves
-multiply on or within the host
-harm the host in some way
Capacity of infection is determined by?
The infective dose
The virulence of the agent
Capacity of a pathogen to spread depends on?
Transmissibility (ability to pass from host to host and ability to survive outside the body)
Infectivity (ability to penetrate host defences)
Pathogenicity (ability of the pathogen to cause disease)
What is horizontal transmission ?
From direct or indirect spread between individuals of the same generation
What is vertical transmission?
From dam to offspring
Hereditary carried within the genome of either parent
Congenital present at birth (either in birth, during birth or colostrum)
What is direct contact ?
Physical contact
Skin surfaces - licking, sleeping, grooming, fighting
Microorganisms cant normally survive for long in the environment
What is indirect contact ?
No physical contact
Animal contaminates the environment with body fluids
Microorganisms transported on fomites or by vectors
Can survive in the environment - varying periods
What is a reservoir ?
The habitat in which the infectious agent normally lives, grows and multiples.
They can inc humans, animals and the environment
Can be where the agent is transferred to the host
What is a fomite?
A contaminated inanimate object
E.g. table, litter tray, floor
What is a vector ?
An animate object that carries microorganisms
Grouped into: biological vector and mechanical (fomites or people carrying disease on shoes)
What is a transport host?
Able to pass infection to other susceptible hosts.
Transport host remains unaffected and acts to maintain viability of other microorganisms
What is a paratenic host?
A species that is not the normal host for a parasite but may be used opportunistically by them.
Acts as a carrier only.
No development of the parasite occurs within this host
Paratenic host must be eaten to pass on infection
What is an intermediate host?
One that shelters the parasite during its immature stage
What is a definitive/final host?
One that harbours the parasite during its adult sexual stage
Infectious diseases pass from one animal to another in 3 stages
- Pathogen leaves infected animal
- Pathogen passes between infected animal and susceptible animal
- Pathogen enters susceptible animal
Time taken for this process can range from milliseconds to years depending on the pathogen
What is a carrier ?
Animals that harbour a pathogen but show minimal or no sign of the disease
They secrete pathogens at intervals
What are convalescent carriers ?
Recovered from clinical disease
-cat flu (FHV and FCV)
-leptospirosis and canine infectious hepatitis
What are healthy carriers ?
Been exposed to infection but show no signs of disease
Patient is said to be immune to that microorganism
E.g - haemobartonella Felis and campylobacter
What is a continuous excretor ?
Can infect other animals at any time
(E.g - cats with FCV shed virus continuously following apparent recovery but most eliminate infection in a few months)
Can remain sub clinically infected for years
What are intermittent excretors?
-excrete organisms under stress
E.g - cats with FHV carry the infection and shed virus throughout life, intermittently, with or without signs of disease, virus dormant between sheds
How do pathogens gain entry to a host?
Ingestion
Inhalation
Direct
MM
Through skin/via skin surface
Congenital
How do pathogens trigger disease
-cells may be destroyed by the pathogen itself
-biological poisons
-response of immune system
What is an incubation period
The interval between contact with the microorganisms and clinical signs of disease
Could be a few days, weeks or years
Speed of infection depends on: agent factors (dose and virulence) and host factors
Prevention of disease transmission
-PPE
-hand hygiene
-isolation wards
-cleaning
-personal hygiene
-barrier nursing
-disinfecting and sterilising equipment
-treatment
-vaccinations
-educating owners
Define isolation
The segregation of an animal or group of animals that are suspected of having or proven to have a contagious disease
Define quarantine
This is the compulsory isolation of animals with unknown disease status for a period of time
Applies to new animal stock and for pet travel abroad
Define barrier nursing
Creates a ‘barrier’ between the infectious animals and the nursing staff and other animals
Usually in conjunction with isolation but can be used on its own if isolation facilities are not available
Define protective isolation
Known as reverse isolation
Involves the isolation of susceptible animals to protect them from potential sources of infections
Isolation and PPE risk table
Level 0 = room empty, no risk, no PPE needed
Level 1 = vaccinated pets, minimal risk to other patients. gloves and apron
Level 2 = quarantine, wild animals, unknown vaccination/disease status, apparently healthy, moderate risk to others, all PPE worn
Level 3 = known/suspected infectious condition. High risk, hand disinfectant, foot bath, all PPE worn and appropriately disposed of.
Level 4 = known/suspected zoonosis, barrier nursing, risk to patients, staff and clients, all PPE worn and appropriately disposed off, foot bath etc.
Define obligate aerobes
Must have oxygen for growth
Define obligate anaerobes
Can only grow in the absence of oxygen
Define facultative anaerobes
Grow aerobically when oxygen is present but can also function in the absence of oxygen
