Exam 1 Flashcards
What type of pathogen is canine parvovirus?
Non-enveloped virus
How is canine parvovirus persistent in the host?
The virus is shed in dogs within 4 to 5 days of exposure
Throughout the disease course and approximately 10 days following clinical recovery. It is not persistent in the host
Is canine parvovirus stable in the environment? If so, how long?
Can persists in the environment for months to years away from sunlight and disinfectants, refractory to most disinfectants (except Bleach)
Does canine parvovirus produce any toxins?
No
How does canine parvovirus enter cells?
Cell mediate endocytosis
Can enter most cells, replicates only in rapidly dividing cells
What is the tropism of canine parvovirus?
Replication in tissue cells that rapidly divide
Lymphoid, intestinal epithelium and in fetal tissue
Invades cells in S phase
Intestinal crypt epithelium and bone marrow hematopoietic precursors
What is the mode of entry for canine parvovirus?
Fecal-oral exposure
How does canine parvovirus structure affect the host response?
Targets and replicated in actively dividing cells
This results in leukopenia and lymphopenia and decreased number of active immune cells able to fight off the infection
What type of pathogen is salmonella?
Rod-shaped
Gram negative bacteria
How is salmonella persistent in the host?
Salmonella=umbrella term
Most common one is S. enterica
Both symptomatic and asymptomatic shedder depending on the species
Is salmonella stable in the environment?
Depends on the strain
usually few hours to several days on surfaces
Does salmonella produce any toxins?
O antigens are associated with the LPS chains that are found in the cell wall of all gram-negative bacteria
How does salmonella enter cells?
Depends on the species
Cell receptor mediated endocytosis is the most common
What is the cell tropism for salmonella?
Depends on the species
Intestinal epithelial cells and macrophages
What is the most common route for salmonella?
Fecal oral
How does salmonella affect host response?
Creates special membrane bound compartments within the host cells to shelter and protect it from host immune mechanisms
What type of pathogen is Rhodococcus equi?
Gram positive bacteria
What is the source of Rhodococcus equi infections?
It is a ubiquitous in the environment
But infected foals shed a tremendous amount of bacteria in their feces
What specific factor is associated with development of Rhodococcus equi?
Animals that produce little to no IFN-y are at an increased risk
What is the tropism of Rhodococcus equi?
Macrophages and replicates when there is a failure of the formation of the phagolysosome after receptor mediated engulfment
This results in an absence of the respiratory burst and destruction of the bacteria
Host factor
How might an animal be exposed to Rhodococcus equi but not develop disease?
Animals are exposed all the time, only those lacking the IFN gamma are at an increased risk
What demographic of horses commonly present with clinical signs of R. equi infection?
Foals 1-4 months old
What are some respiratory pathogens that infect adult horses and not foals?
Equine herpesvirus, equine influenza and equine arteritis virus
What type of pathogen are equine herpesvirus, equine influenza and equine arteritis virus ?
Enveloped viruses
Where is equine influenza typically found?
Maintained in the population by sporadic clinical cases and inapparent infections in susceptible horses
What specific factors is associated with the development of equine influenza?
The virus can mutate and create new strains in a population rapidly
Exposure of the virus to a naive population, particularly those that are immune suppressed
What are the common portal of entry for PRRS?
Direct contact (oral, respiratory, semen)
Indirect (fomites)
Is PRRS persistent within the pig?
Highly persistent in the pig but not in the environment because it is enveloped
What is PRRS tropism?
Macrophage cell
Viremia spread
Trojan horse spread within host
How does the characteristics of PRRS evade the immune system?
RNA virus
Generates mutations
What type of immune response is associated with PRRS?
Humoral (serum neutralizing antibodies) and cell mediated immune response
How does the structure of PRRS affect the immune response?
Enveloped virus
Development of neutralizing antibodies and or cell-mediated immunity have been related with clearance of PRRSV infection
How is the pathogenesis of Ascaris suum different with PRRS?
Ascaris sum is from direct trauma of the parasites migrating through the tissues resulting in secondary bacterial infection
While in PRRS the virus destroys macrophages which decreases the immune response
What are the common portals of entry for Ascaris suum?
Fecal-oral
Paratenic-earthworms and beetles
Is ascaris suum and indirect or direct life cycle?
Direct
Where do adult parasites of Ascaris suum establish infection?
Small intestine
Nematode attaches to the mucosa
What is resulting in the pig’s pneumonia from Ascaris suum
Migration of the L3 larvae through the lungs results in pneumonia
What type of systemic immune response is associated with Ascaris suum and
most helminth infections?
Induce a Th2 response that produces IL-5 and eotaxin that promote eosinophils
Eosinophils are the main leukocyte involved in attacking migrating parasites
What structure on the ascaris suum nematode results in this type of response?
Combination of molting, metabolic waste and migration that triggers the response
How does ascaris suum persists in the environment?
Third stage is infective to the pig
Chitinous structure of the shell protects it from environmental and chemical degradation
The protein coat makes the egg sticky so that it is not washed away
Is there any zoonotic potential of the sanctuary workers contracting Ascaris
suum from their vegetables?
Conflicting reports
May be zoonotic in those that are severely immunocompromised
What are the sources of infection and modes of transmission for canine influenza H3N8?
Direct contact via aerosol or droplets
Source are other infected dogs that are shedding
Once a dog has recovered from canine influenza H3N8 how likely is it that they will transmit it to other dogs?
Low
Dogs often shed disease prior to showing clinical signs
What is the risk of H3N8 influenza persisting for long period of time in the dog?
Low
Not persistent in the host and is not transmitted to humans and does not survive long in the environment
What is the anticipated period of shedding for H3N8 canine influenza?
Highest shedding is first 2-4 days during incubation period but can shed for up to 10-14 days
Is canine influenza H3N8 zoonotic?
No
What type of pathogen is equine infection anemia?
Retrovirus
Lentivirus-enveloped
What are the potential routs of entry for EIA?
Flies
Intermittent feeding, direct contact
What is the tropism of EIA?
Infects macrophages
How is EIA spread within the horse?
Infects macrophages resulting in viremia
What are the various manifestations of disease for EIA?
Acute: fever, non-specific signs, death
Chronic: Animal alternates between remission and disease state, animal is losing condition
Inapparent: Asymptomatic, reservoir for infection, stress may convert to acute form
How is EIA transmitted to other horses?
Flies are mechanical vectors
Direct contact
Are there alternative hosts for EIA besides the horse?
Members of the Equus genus
What does the cogging test test for?
Identifies antibodies for EIA antigen
What are two unique structural features of Roundworm?
Eggs are resistant to harsh environmental conditions
Eggs have pitted shell that is sticky from a protein coat that makes elimination from environment difficult
Transplacental transmission is one of the most important routs of infection to puppies
Single adult female can lay up to 85,000 eggs per day
What are two unique structural features of Porcine Epidemic Diarrhea Virus (PEDV)?
Specific natural host
Virus is enveloped RNA
Easily destroyed
Structural proteins of PEDV interact with viral genomic RNA to protein viral genome forming a nucleocapsid
N protein also perturb antiviral responses
How does roundworm enter the host and cause disease?
Egg ingested
Larvae released in intestines
Larvae migrate to other various organs where development is arrested
How does PEDV enter the host and cause disease?
Virus is excreted in feces
Oral infection due to contaminated food
Viral replication in the epithelial of the small intestine and colonic villi which causes malabsorption of the food and triggers an inflammatory response both leading to diarrhea
Is roundworm zoonotic?
Yes
Is PEDV zoonotic?
No
What are some strategies that break the cycle of transmission in roundworms?
Puppies and kittens dewormed at 2 weeks of age with deworming every 2 weeks until they are 4-8 weeks old
Fecal tests 1-2 times a year
One infectious virus unit
Virion
Lipid bilayer with attachment glycoproteins
Envelope
Are enveloped or naked viruses more stable in the environment?
Naked
Envelope is highly sensitive to drying and detergents
What is the difference between gram positive and gram negative bacteria?
Gram positive= Purple, thick peptidoglycan layer with techoic acids present
Gram negative= pink, lipopolysaccharide layer present
Some bacteria for this to survive adverse environments
Can survive for many months to years in soil
Resistant to heat, dehydration
Antibiotics dont work
Ex: Clostridium tentani
Endospore (Sporulation)
This is the outermost layer covering certain bacteria
Slime made of polysaccharides
Helps to prevent desiccation
Helps in attachment to host cell
Prevents/disrupts phagocytosis
Inhibits lysis by complement
Capsule
What is the main mechanism of protection of eggs/ova?
Shell/Wall
Protein coat that helps it adhere to surfaces
Wall structure may prevent desiccation
Resistant to chemicals
What is the first and most critical step in viral infection?
Attachment
Surface glycoproteins are essential for viral attachment
Viruses have to enter the host cell to replicate
This allows bacteria to bind to host mucosal surface at portal of entry
Adhesions (Fimbria)
Virus is demonstrable continuously whether or not there is ongoing disease
Viral Persistence
Capacity of pathogen to tolerate exposure to lethal concentrations of bactericidal antibiotics
Bacteria, Fungi, Parasite Persistence
Virus is not demonstrable using diagnostic testing except when reactivated
Ex: Herpes
Latent Infection
Infectious virus gradually increases during a very long preclinical phase, leading to a slow, progressive lethal disease
Ex: HIV
Slow Infections
Continuing replication of the virus is not involved in progression of disease
Ex: Fetal infection with feline panleukopenia virus causes cerebellar syndrome in young cats
Acute Infections with Late Clinical Manifestations
Animal has recovered from the illness
No longer has clinical signs by remains in a status that could result in disease transmission to naive host
Often still positive on routine testing
Ex: BVDV
Persistently Infected (Carrier)
The dose of pathogen needed to infect 50% of the population
Infectious Dose
Describes a pathogen’s ability to cause disease
Pathogenicity
Relative measure of pathogenicity
Compares one pathogen’s ability to cause disease compared to another
Virulence
Characteristics that provide the agent an advantage at any step of the infection to cause disease
Virulence Factors
The time from where the pathogen enter the body to first clinical signs
Incubation Period
Incubation period but in parasitology
Time to observation of signs and also time to recovery of infective form
Prepatent Period
Defined by the active shedding of disease
May come before symptoms start to show
Infectious Period
What are 4 reasons a pathogen was unable to establish disease?
Inadequate infectious dose
Virulence of pathogen
Entry of pathogen via wrong route but still resulted in an immune response
Immune response was able to defeat pathogen
What are the common portals of entry for a pathogen into the host?
Mouth
Nose
Conjunctive
Damage to skin
Capillary
Anus
Urogenital
Respiratory
Only produced by gram negative bacteria
Lipopolysaccharides
Released when bacteria is lysed
Heat stable
Cause disease by triggering systemic inflammation
Ex: Salmonella
Endotoxins
Gram - or Gram +
Secreted proteins that act on the host cell
Heat labile
Cause disease by destroying cell wall
Disrupt cell metabolism
Ex: Clostridium botulinum, Staph aureus
Exotoxins
Affinity of the pathogen for certain types of host cells and tissues that support its growth
Largely determine by specific receptors for entry
Specific metabolic requirements for the pathogen
Pathogen may have different this depending on the course of the disease or stage of development
Tissue and Cellular Tropism
Effective for quick widespread dissemination of disease
Free or cell associated
Free pathogen encounter vascular endothelium and macrophages which leads to local inflammation and invasion into tissue adjacent
Bactermia/Viremia/Parasitemia
How do pathogens destroy host tissues?
Damage the immune system
Induce immune system to cause disease
What are some examples of tumor-inducing viruses?
Feline leukemia virus
Feline sarcoma virus
Bovine leukemia virus
Human papillomavirus
Host in which sexual reproduction occurs
Definitive Host
Host in which asexual reproduction occurs
Intermediate host
Host in which no reproduction occurs
It is just keeping the parasite alive until its eaten by the next host
Often this is tastier than the intermediate host
Paratenic Host
Maintains the parasite in the environment
The whole life cycle or just part of it may be maintained in wildlife
Presents a problem or eradication
Reservoir Host
Only one host needed to complete the life cycle
Direct Life Cycle
Need two or more hosts
One host is the definitive host where sex occurs
One or more hosts are intermediate where asexual reproduction or development from one stage to another occurs
Indirect Life Cycle
What host is the definitive host in the heartworm life cycle?
Dog
What host is the intermediate host in the heartworm life cycle?
Mosquito
Parasites are often very specific for their host
If it ends up here it will not be able to develop
They behave as if they are lost
Accidental (Dead-End) Host
Spreads through direct or indirect contact
Fomites
Airborne
zoonotic
Horizontal Mode of Transmission
Spread from dam to embryo or fetus
During or shortly after parturition to newborn
Vertical Mode of Transmission
A susceptible host contracts an infection by physical contact with an infected host
Percutaneous
BItes (monkeypox)
Direct Transmission
Intermediary vehicle that transmits the infectious agent between infected and susceptible hosts
Fomites
Indirect Transmission
Transmission by the doctor
Contamination with pathogen during medical or surgical procedures
Dirty instruments
Iatrogenic
When an insect vector is involved in transmission of the disease
Arthropod-borne Transmission
Carry pathogens that can multiply within their bodies and be delivered to new hosts, usually by biting
Infectious agent replicates in vector
Biological Vectors
Simply convey pathogens to a susceptible individual and is not essential to the development of the organism
Physical transfer of infectious agent only
Mechanical Vector
Hospital acquired infection
Nosocomial
Disease of vertebrate animals that can be transmitted to man
Zoonoses
The population of organisms or the specific environment in which an infectious pathogen naturally lives and reproduces or upon which the pathogen primarily depends for its survival
Does not result in severe disease in this host
Reservoir
Severe fever and non-specific signs developing 2-3 weeks after exposure
Virus is most actively replicating
May result in death
Acute Disease Form
Animal alternates between remission and disease state
Animal losing condition
Swamper
Chronic Disease Form
Asymptomatic
Acting as reservoir of infection
Lower virus concentration in blood, stress may convert to acute form
Inapparent Disease Form
An eosinophilic virus inclusion body is?
Intracellular collection of virions
Negative staining
Strengths: Visual image, structural
Limitation: Presence of large number of particles required, viruses with similar morphology difficult to distinguish
Electron Micropscopy
Test samples are either inoculated in embryonated eggs or cell cultures
Strengths: Unknown is possible, come up with an isolate for further characterization
Limitations: Not all viruses can be isolated
Virus Isolation
The most rapid and effective way to test for rabies virus in suspect tissue from wildlife is?
Immunofluorescence
Differentiating infected from vaccinated animals
DIVA
The test for FeLV tests for what?
Antigens
The test for FIV tests for what?
Antibodies
What is the most common diagnostic for viruses?
PCR
Evaluate consistency, color, blood, intact worms, tapeworm segments
Gross Examination of Feces
Used to evaluate motile forms of parastates
only need a small amount of feces
Overall low sensitivity
Need to evaluate within 25 minutes of collection
Good for giardia or trich
Saline Direct Fecal Smear Examination
Floats common helminth and protozoa eggs/cysts
preferred for flotation of giardia and some lungworm larvae
Less effective for tapeworm
Does not float flukes
SG: 1.18
Zinc Sulfate
Floats common helminth and protozoa eggs/cysts
Distorts giardia cysts
Does not float flukes and some tapeworm and nematode eggs
SG: 1.2-1.33
Sodium Nitrate
Floats common helminth and protozoa eggs/cysts
Distorts giradia cysts
Does not float flukes
SG: 1.2
Sodium Chloride
Floats common helminth and protozoa eggs/cysts
Preferred for floation fo cryptosporidium oocysts
Causes less damage to parasite eggs than salt
Does not float flukes
Less sensitive than zinc for giardia
sticky
SG: 1.25
Sugar Solution
Floats common helminth and protozoa eggs/cysts
Distorts giardia
Does not float flukes
SG: 1.32
Saturated Magnesium Sulfate
Let float sit for too long
Not a fresh sample
Too small a sample
Pseudoparasite or egg
Coprophagy
Fecal Floatation Errors
Sensitivity 1-5 epg
Easier for animals that you expect lower egg counts naturally
Technique of choice for the quantification of helminth ova
Wisconsin Technique
Sensitivity 100 epg
Easier for animals with higher egg counts
Technique of choice for the quantification of protozoan structures
Modified McMaster’s Technique
Used to recover dense eggs that do not readily float in common flotation solutions
Flukes and tapeworms
Less sensitive for detecting nematode eggs, coccidian oocysts, larvae or giardia
Fecal Centrifugal Sedimentation
Technique used to isolate nematode larvae from fresh fecal samples
Principle of this test is that the nematode larvae cant swim against gravity when completely immersed in water
Stronglyoides
Dictyocaulus
Baermann Exam
Inhibits microbial metabolism and growth
Does not kill the microbe
Ex: Tetracycline
-Stasis/static
Permanently inactivates microbes
Ex: Penicillin
-cide/cidal
Uses chemicals, processes, or environmental conditions to destroy or eliminate all microorganisms on non-living objects
Physical
Mechanical
Chemical
Sterilization
Mechanism of action is it denatures proteins
Autoclave
Pasteurization
Heat Sterilization
Mechanism of action is to create DNA breaks in bacteria and inhibit cell division
Requires the use of radioactive isolate cobalt 60
Used to sterilize single use plastic
Gamma Radiation
Hand washing
Air filtration
Mechanical Sterilization
An agent that kills microorganisms or stops their growth
Antimicrobials
Chemicals that are applied to non-living surfaces to prevent or inhibit growth of microorganisms
Nondestructive to surfaces
Biodegradable
Disinfectants
Chemicals that are applied to the surface of living organisms or tissue to prevent or inhibit growth of microorganisms
Applied on tissues to suppress or prevent microbial infection
Non toxic to host tissue
Does not impede or delay healing
Antiseptics
Disinfectant
Disrupts DNA of microorganisms
Kills bacteria, spores, fungi, and viruses
Gas sterilization of heat sensitive items
Carcinogenic to humans
Needs special equipment to use the gas
Ethylene Oxide
Antiseptic
Damage cell wall especially in gram negative nacteria
Pseudomonas aeruginosa
proteus vulgaris
E. Coli
Staph auerus
Ear cleaning
Tris-EDTA
antiseptic and disinfectant
Denatures proteins, dissolves lipids and desiccates surfaces
Bactericidal
Virucidal against enveloped virus
Not effective against spores or prions
Water is required to be effective
Ethyl and isoproply
Alcohol
Disinfectant and antiseptic
Denatures proteins
Formaldehyde (foot baths)
Glutaraldehyde (cold sterilization)
slow acting
Aldehyde Compounds
Antiseptic
Distrupts negatively charge microbial cell membrane
Limited activity against mycobacteria and fungi
Effective against enveloped viruses
Not effective against spores or prions
Maintains activity in presence of organic material
Chlorhexidine
Disinfectant
Oxidation of peptide links and denaturation of proteins
Organic matter reduced efficacy
Broad spectrum bactericidal and everything else
Chlorine Compounds
Antiseptic and Disinfectant
Denatures proteins in cytoplasmic membrane
Blood reduces efficacy
Limited activity with non-enveloped virus
Effective against spores after 15 min
Naval treatment
Pyoderm
Iodine
Disinfectant
Denatures proteins and lipids
Works on most bacteria and viruses
Not effective against spores
Plasma sterilization of equipment that can not be steam sterilized
Remove blood from clothing
Hydrogen Peroxide?
Disinfectant
Denatures proteins and lipids
Works on most bacteria and viruses
Not effective against spores
Plasma sterilization of equipment that can not be steam sterilized
Remove blood from clothing
Hydrogen Peroxide
Disinfectant
Denatures proteins and disrupts cell walls
Effective in presence of organic material
Skin irritant
Kills most bacteria but best at gram +
Effective against enveloped viruses
Phenols
Disinfectant
Denatures proteins and binds to phospholipids of cell membranes
Effective against gram positive and enveloped viruses
Quaternary Ammonium Compounds
The ability for a pathogen to attach to a host cell is an important virulence factor for all pathogens. Which of the following virulence factors is used specifically for attachment in bacteria?
Fimbria
A unique property of parvoviruses determines the tropism of the virus in its host. Which cell types would effectively support parvovirus replication?
Hematopoietic precursors
Virus Z takes about 45 – 60 days to cause clinical signs in a dog after infection. The virus is shed by the animal 3 days before clinical signs appear and shedding continues for about 7 days after clinical disease starts and the animal dies. What is the infectious period of virus Z in a dog?
10 days
In bacteriology and virology, the incubation period is defined as the point from when the pathogen enter the body to first clinical signs. What is this time period called in parasitology?
Prepatent period
Hamilton is a 10 week old, male intact, Boston Terrier dog that is presenting for fever, lethargy, leukopenia (low white blood cells), and severe foul-smelling diarrhea. After treating him for several weeks in the hospital for Canine parvovirus (CPV), you are interested in determining if he has begun to mount an immune (host) response to the virus.
Which sample and test would you recommend to determine if Hamilton has mounted a host response?
serum; CPV antibody ELISA
A new deadly respiratory disease is sweeping through the pig farms in Iowa with major fears that quickly will have huge consequences on the food supply. This pathogen has been challenging to isolate using routine diagnostic testing methods. As a last-ditch effort to determine the cause for the disease, your team decided to determine what the disease is, based on the structural and morphologic characteristics of the pathogen.
Which uses the structural morphology of an organism to make a diagnosis?
Electron Microscopy
You are called out to a farm with 200 Virgin Island White sheep that the producer has been deworming every other month with ivermectin for Haemonchus contortus. Over the past month, he has been losing 5-6% of his flock and on necropsy thousands of small barber pole appearing nematodes are observed and consistent with Haemonchus contortus. To gain a better understanding of which animals are the high egg shedders, you decided to run a quantitative fecal exam.
Which technique would you recommend?
McMaster’s exam
Which bacterial diagnostic techniques uses mass spectrophotometry and bacterial proteomics to identify a pure culture?
MALDI-TOF (Matrix-Assisted Laser Desorption Ionization Time-of-Flight)
Which of the following techniques or tests can be used to detect either antibodies or antigens depending on the test design?
ELISA
What is specifically being tested for in the ELISA snap test for FeLV
p27 FeLV structural antigen present in the blood of infected individuals
