Lab 3.1: Detection of Disease Flashcards
sensitivity and specificity def
- Sensitivity: represents the likelihood that an animal with a disease will have a positive test result
- Specificity: represents the likelihood that an animal without a disease will have a negative test result
what are primary and secondary cell lines for virus isolation in cell culture?
I. Primary cell line: prepared directly from animal tissue tissues e.g. kidney, lung, spleen - no sub-cultivation
II. Continuous cell line: these type of cells are transformed for indefinite sub-cultivation. Most frequently used in diagnostic virology
what are the visual signs of a cytopathic effect in cell culture?
Cytopathic effect (CPE)
-Rounding and clumping of cells
-Vacuolation
-Fusion of cells; Syncytia or giant cells
how does immunofluorescence work?
antibody with indicator attaches to viral antigen, then visualized
how does ELISA work?
ELISA: Enzyme - linked Immunosorbent Assay for antigen detection
capture antibody on test sheet attaches to target antigen, and then enzyme-linked detection antibody sweeps over
what is the most versatile, rapid, sensitive and specific test for virus ID?
- Polymerase chain reaction (PCR) and its variations
virus neutralization test
-known amount of virus is added to each well
If enough antibodies are present, they will neutralize the virus and the cells will NOT become infected and NO cytopathic effects will be appreciated
- Which one of the following is CORRECT about diagnostic virology?
a) A rapid test is preferable to a sensitive test?
b) Virus visualization is more important than detecting its nucleic acid
c) Sequencing is not routinely performed for diagnostic testing?
d) Virus isolation is routinely done for diagnosis of animal infections
c) Sequencing is not routinely performed for diagnostic testing?
- Which one of the following is NOT CORRECT about diagnostic virology?
a) Nasal discharge is almost always important sample for all virus infections?
b) Viruses are not alive outside of the infected tissue so storage temperature during shipment WILL NOT affect the diagnostic result
c) There is no need to use personal protective equipment during sample collection since the type of virus is not yet known
d) Diagnostic tests are not that important for disease control and prevention
e) All of the above
f) All except B
e) All of the above
general approaches to treatment of CPV
- Intravenous fluids (balanced electrolyte solution)
- Antibiotics to prevent secondary bacterial infection
- Antiemetics (persistent, severe vomiting)
prognosis of CPV?
- 68-92% of puppies administered appropriate supportive care will survive, having developed long-term (potential life-long) immunity against the virus.
- Recovery time: Approximately 1 week after surviving the first 3-4 days of illness
what to expect in post mortem for CPV
Small intestine:
* Severe necrotic and hemorrhagic enteritis
* Necrosis in the Peyer’s patch
Lymph nodes (intestinal, mesenteric):
* Multifocal hemorrhage
Thymus:
* Severe diffuse hemorrhage (not pictured)
Vaccination strategies for Parvovirus
Inactivated and modified-live vaccine at 6–8, 10–12, and 14–16 weeks
- Booster administered 1 year later and then 3 year later
- Usually given as a combination CORE vaccine→ DAPP (Distemper, Adenovirus, Parvovirus, Parainfluenza) or DHPP (Distemper, Hepatitis, Parvovirus, Parainfluenza)
- Inactivated vaccines for pregnant bitches (reduced risk of abortion)
why might vaccines fail?
- Faulty vaccine - improper storage or administration
- State of immune system at time of vaccination
○ Immature immune system and/or dog is unhealthy at time of vaccination - Breed Differences!
○ Rottweilers and Dobermans are more susceptible to developing parvovirus enteritis despite vaccination! - Maternal immunity - maternal antibodies block the live attenuated vaccine challenge
● Ideal timing of vaccination: when the maternal antibodies levels will be low enough to no longer protect the dog
when is a puppy most vulnerable to CPV and why?
Puppy is most vulnerable to CPV-2 if infected between 8 to 16 weeks old
-period between maternal antibody protection and vaccine protection
when is parvovirus shed and how?
Virus is shed in the feces of infected dogs within 4–5 days of exposure (often before clinical signs develop), throughout the period of illness, and for ~10 days after clinical recovery
how do we kill parvo in the environment?
Killing parvovirus (small naked DNA virus) requires
strong disinfectants:
● Bleach (sodium hypochlorite)
● Potassium peroxymonosulfate
● Hydrogen peroxide
- Quaternary ammonium (soap) disinfectants do not kill parvovirus
Marek’s disease lifecycle
Mdv invades lung air space and infects epithelial cells
> MDV infects cells and spreads to the feather follicales to replicate
>birds shed MDV perticles in skin dander
>birds inhale MDV particles from dust in the environment
how do we vaccinate for Marek’s disease?
In OVO! We can vaccinate 18-day-old embryos! The chick has the best possible start when it hatches and
better disease resistance from day one
Manual subcutaneous vaccination is susceptible to human errors, while in ovo vaccination systems deliver the right dose in the right location
Why do animals get diseases if they have been vaccinated against?
- Particularly virulent strain of virus
Vaccine failure?
* Wrong administration route
* Not administered in correct quantity
* Poor preservation (e.g. vaccine got too hot/cold/old)
- Non-responder to the vaccine / immune status?
- Maternal antibody interference?
- Vaccine does not prevent infection, but prevents disease!
What viruses cause erosive/ulcerative mouth lesions? (6)
Bovine viral diarrhea virus (Flavivirus)
Foot and mouth disease (Picornavirus)
Infectious bovine rhinotracheitis (Alphaherpesvirus) Malignant catarrhal fever (Gammaherpesvirus)
Rinderpest (Paramyxovirus)
Vesicular stomatitis (Rhabdovirus)
*Progressing severe watery bloody diarrhea in young animals
*Oral mucosal ulceration
*Poor-doing calves (scruffiness, poor coordination, small) *Distal limb erosions
=>what diseases fit these symptoms?
*Clinical presentation could fit with mucosal disease OR severe, acute BVDV
How do you test a dairy herd for BVDV?
200 mL of milk from a bulk tank can be pooled from up to 400 animals
If the test is negative: you know every animal who contributed to the bulk tank is negative
If the test is positive: milk should be retested in 3 weeks to rule out acute infection
If the bulk milk sample is positive a second time: you need to evaluate animals individually
How can we control and prevent BVDV?
Identification and elimination of persistently infected animals in a herd > also need to test any replacement animals!
Vaccination:
* At least ten different brands of BVDV vaccines in North America
* Ideally you would want to choose a vaccine that works against both BVDV 1 and 2
Feline calicivirus vaccination
- Like many RNA viruses, there is variation between strains of feline calicivirus
- Creates a challenge with vaccination
- Vaccines are either single or dual strain
- Vaccination does not prevent infection, prevent carrier state, or protect against virulent strains
how does PRRS spread in a naive herd? in an endemically infected herd?
○ In a naive herd: infection spreads slowly throughout herd causing clinical picture as in this case with variable degrees of disease and death
○ In an endemically infected herd: infection is often subclinical
how is PRRS maintained in a herd? in what herds are the greatest losses seen?
○ Virus is maintained in a population indefinitely by asymptomatic swine who shed the virus for up to 3-5 months
● Greatest losses are seen in herds experiencing other concurrent infections
what part of the body does PRRS destroy and what is a result of this?
Virus destroys pulmonary alveolar macrophages → risk of secondary bacterial pneumonia
what season is conducive of PRRS spread?
Virus survives at low temperatures, so epidemic spread is quite efficient in the winter months
how is PRRS transmitted?
● Virus transmission is by direct contact, airborne and via semen
what PRRS signs do we see post mortem?
Lungs: Red, rubbery, do not collapse→ consistent with interstitial pneumonia
how do we control PRRS?
● No single effective control strategy
● Often goal is to create a “PRRS stable” farm through intentional exposure of entire stock (before breeding)
● Vaccination: commercial modified live PRRSV vaccine (IM) and inactivated vaccines exist; efficacy variable against circulating strains
● Elimination on individual farm very difficult due to long shedding period, asymptomatic carriers, and extreme biosecurity measures required for maintenance (including massive initial depopulation)
Long-term consequences of Canine Distemper
-Can occasionally see foot pad hyperplasia and enamel hypoplasia in dogs that were acutely infected and managed to survive the infection
-Can also see permanent neurological damage
What are the post-mortem findings for canine distemper?
The pathologist found mild multifocal to coalescing
bronchopneumonia, encephalitis and myelitis in several affected dogs
Characteristic inclusion bodies were seen in H/E-stained brain, lung, stomach, urinary bladder
how do we vaccinate for canine distemper
Modified-live vaccine
* Usually given as a combination vaccine→ DAPP
(Distemper, Adenovirus, Parvovirus, Parainfluenza) or DHPP (Distemper, Hepatitis, Parvovirus, Parainfluenza)
Inactivated vaccines for pregnant bitches (reduced risk of abortion)
what test do we use to detect FIV? what about FeLV?
- FIV Antibody detection
- FeLV is Antigen detection
Should we be concerned about false positive results for FIV? why?
- FIV Antibody detection
- Infected mother transfer FIV antibodies to nursing kittens
Key fact: when a cat is first infected with FIV, its immune system develops antibodies against the virus that persist in the blood for the rest of its life
what is the prognosis for FIV, in general?
- The lifespan of FIV infected cats is highly variable
- With management, cats can often live “normal” lives
- Cats with the virus can be asymptomatic for a long time
- More than 50% are asymptomatic for 5 years
- 20% die within 2 years of diagnosis (which is often 4-6 years after infection if they are not tested until they are symptomatic)
HOW DO WE TREAT/control FIV?
- Visiting the veterinarian at least every 6 months
- CBC, biochemistry, and urinalysis recommended
- Promptly treating secondary infections
- Providing a balanced diet (no raw foods)
- Controlling parasites
- Antiviral Zidovudine (AZT, Reverse transcriptase inhibitor)
- Reduce viral replication, but side effects
- FIV-infected cats should be spayed or neutered and kept indoors to minimize exposure
What should be done to prevent FIV transmission?
- The most important measure for the control of FeLV and FIV is the identification and segregation of infected cats!
- Cats of unknown retrovirus status should be housed individually in shelters
- FIV-infected cats should be spayed or neutered and kept indoors to minimize exposure
histologically, we see a sheep brain with spongiform changes in gray matter. How can we investigate further?
ELISA test for scrapie
-Immunohistochemistry and western blot are used to confirm - gold standard
techniques
is scrapie reportable?
yes, in canada
how to deal with scrapie once it is found on a farm
- Thorough investigation of his farm
> flock records, including births, sales and exchanges of animals for at least the last 5 years
> incidents of commingling with other sheep or goats from other farms - Scrapie susceptibility testing by the CFIA
> All sheep (9 months and older) will be genotyped - Destruction and disposal based on genotyping results
> Those animals considered to be at low risk (resistant) for scrapie infection are allowed to remain on the farm
> Those animals considered to be intermediate and high risk (susceptible) for scrapie infection should be destroyed - Cleaning and disinfection (prions are very resistant)
- Surveillance (5 years)
> Any sheep or goat over 12 months that dies or is euthanized on farm may be tested for scrapie
