Infectious Dz - Feline Retroviruses and FIP Flashcards
What type of viruses are retroviruses?
Enveloped RNA viruses
How do retroviruses work?
Their RNA is reverse transcribed into DNA and then integrated into the host’s genome
Where is Feline Immunodeficiency Virus (FIV) distributed?
Worldwide - 2.5% prevalence in the US
There are 5 subtypes of FIV. Which subtypes predominate in the US?
Types A and B
How is FIV transmitted?
Mainly through bite wounds, but transplacental transmission is also reported
What are the risk factors for FIV?
Older male, outdoor access, history of fighting, and FeLV infection
What are the phases of FIV infection?
acute, subclinical, and terminal
Characterize the acute phase of FIV.
Viral replication in lymphoid tissue Viremia Decrease in CD4 and CD8 T cells Neutropenia Mild transient illness - anorexia, fever, and diarrhea
Characterize the subclinical phase of FIV.
Asymptomatic Significant drop in viremia Progressive decrease in CD4/CD8 ratio Hyperglobulinemia Altered immune function
Characterize the terminal phase of FIV.
Susceptibility is opportunistic
Neoplasia
Neurologic diseases
Do all cats reach the terminal phase of FIV?
No, some cats may not progress to it
What are the clinical manifestations of FIV?
Gastrointestinal - stomatitis and diarrhea
Neurologic - behavioral changes and locomotor abnormalities
Ocular - anterior uveitis, glaucoma
Neoplasia - Lymphoma and acute leukemia
What is the main problem when you have a patient present for illness and you discover that they have FIV?
You have to determine if FIV was actually the cause of the disease. ALWAYS evaluate for other underlying infections/diseases.
How is FIV diagnosed?
ELISA antibody test
What can cause false positives on the ELISA antibody test for FIV?
FIV vaccinated cats and kittens less than 6 months of age because they could have maternal antibodies
When should you test for FIV?
Test all new cats and then repeat in 60 days
Test all sick cats regardless of prior testing
Test all cats with possible exposure to FIV positive cats and repeat in 60 days
Test all blood donor cats
Test prior to FIV vaccination
Why do you want to retest some cats in 60 days?
Because they may not have developed any antibodies at the time of testing. The 60 day window should give ample time to develop antibodies if they are in fact infected
What should you do if you get a positive FIV result in a patient that is less than 6 months of age?
Retest every 60 days until they reach 6 months of age. If it is still positive at 6 months then consider the patient infected.
What should you do if you get a positive FIV result in a patient that is greater than 6 months of age?
Retest immediately. If positive and not vaccinated, the cat is considered infected.
What should you do with a negative FIV test?
Believe it. The ELISA test is very reliable. If you are suspicious of exposure then retest in 60 days.
What other infectious agents could cause uveitis in patients with FIV?
T. gondii and C. gatti
What other infectious agent could cause the stomatitis in patients with FIV?
Calicivirus infection
For what cats is treatment of FIV reserved for?
Cats in the terminal phase of FIV
What is the treatment for FIV?
Supportive care
Darbepoetin or GM-CSF for cytopenias
Antivirals - AZT and Fozivudine
What should be done for patients that are infected with FIV and asymptomatic?
Prevention should be prioritized. Keep indoors, neuter/spay, do not feed raw foods, and if hospitalized isolate but do not put in infectious disease ward
Is the FIV vaccine recommended?
No. Commercial vaccines are not available anymore. The efficacy is questionable
How long can cats have circulating antibody if given the FIV vaccine?
Up to 4 years
Can cats be vaccinated for other diseases if they have tested positive for FIV?
Yes. Most cats can mount an adequate immune response. Inactivated vaccines should be used.
What is the prognosis for FIV?
Good - multiple studies have shown no difference between mean survival time in positive and negative cats
There are 3 subgroups for Feline Leukemia Virus. What is subgroup FeLV-A?
It is the only subgroup that is infectious
There are 3 subgroups for Feline Leukemia Virus. What is subgroup FeLV-B associated with?
Lymphomas and neuropathy
There are 3 subgroups for Feline Leukemia Virus. What is subgroup FeLV-C associated with?
non-regenerative anemia
How is FeLV transmitted?
Licking/grooming (most common), shared food/water bowls, biting/fighting, and transplacental transmission
What are the risk factors for FeLV infection?
Access to the outdoors, FIV infection, contact with other cats, male, young cats (1-6 years)
What is the overall prevalence of FeLV?
1-6% overall
What are the types of FeLV infection?
Abortive, focal, regressive, and progressive
Characterize the abortive FeLV infection.
Robust immune response clears the virus and there is no viremia (negative antigen test)
Characterize the focal FeLV infection.
Proviral DNA is present in some tissues (not in blood or bone marrow) but there is a negative antigen test
Characterize the regressive FeLV infection.
Integration of proviral DNA into the host genome of most tissues (limited in bone marrow and lymphoid tissue)
Transient antigenemia/no shedding
Can be reactivated with sickness or immunosuppression
Characterize the progressive FeLV infection.
Infection of lymphoid tissue and bone marrow.
Active replication and shedding - p27 Antigen-positive
How does FeLV cause neoplasia?
There are insertional mutations caused by viral integration
What are the most common neoplasias caused by FeLV?
Lymphoma (60x more likely than non-positives) and acute leukemia
Is anemia due to FeLV regenerative or non-regenative?
non-regenerative
What presentation of anemia should make you very suspicious of FeLV infection?
Presence of macrocytic anemia without reticulocytes
Why are cats with FeLV more susceptible to infection from other infectious agents?
Because their immune system is impaired
When should you test for FeLV?
Same indications for FIV testing
If you retest for FeLV, when should you do it?
In 30 days - it has a shorter seroconversion
What is the first line screening test for FeLV and what does it detect?
ELISA antigen test which detects p27 capsid protein
What should you do if you get a positive result on the FeLV antigen test?
Repeat ELISA but with another company’s antigen test or perform an IFA on a blood smear or bone marrow sample
What should you do if you get a negative result on the FeLV antigen test?
If you suspect previous exposure then retest in 30 days
When would PCR be beneficial in diagnosing FeLV?
If there is a suspected regressive infection. Since there is no circulating antigen a ELISA test will not pick it up
How is FeLV treated?
Supportive care and antivirals
What is the prognosis for FeLV?
Decreased survival time, 4 years, in postive cats
What is different about lymphoma caused by FeLV than lymphoma that is not?
Cats with lymphoma caused by FeLV have decreased response to standard chemotherapy protocols
What should be done for patients that are positive for FeLV (not treatment related)?
Keep them indoors, no raw food diets, use inactivated vaccines, and separate from negative cats
Who should be vaccinated for FeLV?
All kittens should be vaccinated but subsequent vaccinations should be based on lifestyle
If you suspect FeLV and your cat is vaccinated should you still test for it?
Yes because the level of vaccine protection is unclear
What type of viruses are feline coronaviruses?
ssRNA(+) viruses that are large enveloped viruses with large glycoprotein spikes
What are the two feline coronaviruses?
Feline enteric coronavirus (FECV) and Feline infectious peritonitis (FIP)
What is the pathogenicity of feline coronaviruses?
low
What type of disease does FeCV cause?
a self-limiting enteric disease
What type of disease does FIP cause?
severe systemic disease
How are feline coronaviruses transmitted?
Oral fecal transmission - carriers can start shedding at any point in their lifetime
What cells does FeCV infect?
apical enterocytes
What does mutation during FeCV infection result in?
Gaining capacity to replicate inside macrophages which allows for systemic access and protection from destruction inside macrophages
Can FCEV convert into FIP?
yes
How does FCEV convert into FIP?
Via mutations at the 3C gene, spike gene, and/or S1/S2 Furin cleavage site
What are the risk factors for developing FIV?
Intensity of FECV exposure - regulat introduction of new cats
Age of infection (early on in life)
Genetics
Stressors/immunosuppression
At what age is FIP typically found in cats?
Between 3 months and 3 years of age
What breeds more commonly get FIP?
Purebred cats
What are the two forms of FIP?
wet and dry form
Describe the wet form of FIP.
Large amounts of fluid (exudate) - pleural, pericardial, and abdominal exudate
Low cellularity/high protein content
Describe the dry form of FIP.
Pyogranulomatous/granulomatous inflammation affecting various organs
What does FIP infect?
macrophages and monocytes
What is clearance of FIP based on?
robust cellular immunity
If there is inadequate cellular immunity and strong humoral immunity, what form of FIP will you get?
wet form
If there is partial cellular immunity, what form of FIP will you get?
dry form
Why can humoral immunity be good for FIP?
One study found that the clearance of the virus was correlated to levels of a specific antibody (spike)
Why can humoral immunity be bad for FIP?
High antibody titers contribute to inflammation and effusion by type III hypersensitivity
Binding of antibodies to the virus may increase phagocytosis - antibody dependent enhancement of virulence
What will you find on PE in patients with FIP?
vague signs, weight loss, fever, ICTERUS, uveitis/chorioretinitis, and neurologic signs
What will you find on PE in patients with the wet form of FIP?
dyspnea, muffled heart/lung sounds, and abdominal distension
What will you find on PE in patients with the dry form of FIP?
lymphadenomegaly (intestinal), intestinal masses, and renomegaly
What is the gold standard diagnostic test for FIP?
Intralesional detection of the virus (immunochemistry) at necropsy
How is FIP diagnosed ante-mortem?
Combination of signalment/history/PE, clinical pathology, imaging, and specific viral testing
What specific viral testing can be done for FIP?
Antibody detection, RNA detection (not great), and immunocytochemistry
What will you find on CBC in patients with FIP?
Non-regenerative anemia and lymphopenia
What will you find on serum chemistry in patients with FIP?
Hyperbilirubinemia, hyperglobulinemia (usually polyclonal), hypoalbuminemia, and a decreased serum albumin/globulin ratio
In the wet form of FIP, you can do effusion analysis. What will you find?
Exudate, neutrophilic/macrophagic inflammation, and a decreased fluid albumin/globulin ratio
What test can be done for effusion analysis in patients with the wet form of FIP?
Rivalta test
When can false positives occur with the Rivalta test?
if there is lymphoma or peritonitis
What will you see on diagnostic imaging for FIP?
Cavitary effusion and organomegaly
What does a positive serology result mean in FIP cases?
That the patient has some sort of coronavirus but it cannot distinguish what kind
What is the value of serology when testing for FIP?
Negative results can help rule out FIP
What can cause a false negative serology result when testing for FIP?
Rapidly progressive disease and end-stage disease
What is the value for RT-qPCR?
negative results can help rule out FIP
What can cause a false negative RT-qPCR test?
low sample load, RNA degradation, and inappropriate protocol
How does an immunocytochemistry work?
It uses antibodies to detect the virus in macrophages from a sample
What does a positive immunocytochemistry result indicate?
If properly performed, it is suggestive of FIP
What does a negative immunocytochemistry result indicate?
The cat does not have FIP or FCOV
What can cause a false negative immunocytochemistry result?
low numbers of macrophages or viral particles
What is the prognosis for FIP?
Grave - no cure
What can be given as a ‘treatment’ for FIP?
Immunosuppressives to decrease inflammation and slow viral replication
Antivirals - 3C-protease inhibitors
How is FIP prevented?
vaccination, sanitation, husbandry
What type of vaccine is there for FIP? Is it recommended?
Intranasal vaccination - no proven efficacy so it is not recommended
What husbandry steps can be done to prevent FIP?
Decrease the number of cats, increase the adult:young ratio, hygeine, eliminate chronic shedders, wait 2 months prior to getting a new cat if your cat died from FIP
Is there evidence of reverse zoonosis for COVID 19 in animals? Zoonosis?
Reverse zoonosis - some cats/dogs of people with COVID 19 have had genetic material of COVID19 on PCR
Zoonosis - no evidence
