Infectious Dz - Feline Retroviruses and FIP Flashcards by Jessica Carson

What type of viruses are retroviruses?

Enveloped RNA viruses

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How do retroviruses work?

Their RNA is reverse transcribed into DNA and then integrated into the host’s genome

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Where is Feline Immunodeficiency Virus (FIV) distributed?

Worldwide - 2.5% prevalence in the US

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There are 5 subtypes of FIV. Which subtypes predominate in the US?

Types A and B

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How is FIV transmitted?

Mainly through bite wounds, but transplacental transmission is also reported

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What are the risk factors for FIV?

Older male, outdoor access, history of fighting, and FeLV infection

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What are the phases of FIV infection?

acute, subclinical, and terminal

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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

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Characterize the subclinical phase of FIV.

Asymptomatic
Significant drop in viremia
Progressive decrease in CD4/CD8 ratio
Hyperglobulinemia
Altered immune function

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Characterize the terminal phase of FIV.

Susceptibility is opportunistic
Neoplasia
Neurologic diseases

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Do all cats reach the terminal phase of FIV?

No, some cats may not progress to it

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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

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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.

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How is FIV diagnosed?

ELISA antibody test

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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

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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

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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

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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.

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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.

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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.

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What other infectious agents could cause uveitis in patients with FIV?

T. gondii and C. gatti

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What other infectious agent could cause the stomatitis in patients with FIV?

Calicivirus infection

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For what cats is treatment of FIV reserved for?

Cats in the terminal phase of FIV

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What is the treatment for FIV?

Supportive care
Darbepoetin or GM-CSF for cytopenias
Antivirals - AZT and Fozivudine

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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