Feline Immunodeficiency Virus

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Feline Immunodeficiency Virus

Feline Immunodeficiency Virus, or FIV, is a retrovirus that infects felines only (it cannot spread to people, dogs or other animals). FIV is found around the world but is not as prevalent as the Feline Leukemia Virus. FIV is most common in adult, male cats that are allowed outdoors. Continue reading to learn more about this virus, how it’s transmitted, and how to protect your cat!

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Feline Immunodeficiency Virus Transmission

FIV is a retrovirus that is spread primarily in the saliva by deep bite wounds. Rarely, the virus can spread to other cats in the same household that don’t fight with one another. Queens (mother cats) can infect their kittens in utero through the placenta or after the kittens are born and are nursing.

FIV Infection Stages

There are 4 main stages of infection caused by FIV and not all cats will develop each stage.

  1. Acute Stage: This begins shortly after infection, often within 1 to 2 weeks. Symptoms include fever, lethargy, and enlarged lymph nodes.
  2. Latent Stage: Infection becomes asymptomatic after the Acute Phase and can last for months to years.
  3. Acquired Immunodeficiency: Reduced immune function leading to increased risk of secondary infections and immune-mediated diseases. This stage often develops years after the initial infection.
  4. Terminal Phase: End-stage of infection and symptoms can include cancer formation, secondary infections, neurologic issues, etc. Once this stage develops, survival time is often just 2 to 3 months.

Diseases Caused By FIV and Symptoms to Monitor For

(please note, many of these are similar to Feline Leukemia Virus as most symptoms result from immunosuppression and secondary infections)

  • Cancers, such as Lymphoma and Leukemia
  • Low red blood cells (anemia) causing weakness, pale gums, and organ dysfunction
  • Low platelets (thrombocytopenia) which can cause spontaneous bleeding or bruising
  • Low white blood cell counts leading to increased infection risk, especially upper respiratory tract infections and potentially severe skin infections
  • Kidney disease
  • Eye changes such as glaucoma, inflammation in the eye chambers, conjunctivitis, and cataract formation
  • Neurologic Disorders such as change in behavior, abnormal sleeping patterns, abnormal gait (walk), and seizures
  • Diarrhea, weight loss, vomiting, reduce appetite
  • Abortion or stillbirth
  • Fever
  • Enlarged Lymph Nodes
  • Severe gingivitis/stomatitis (oral inflammation)
  • Drooling
  • Bad breath (halitosis)

How does my vet test my cat for Feline Immunodeficiency Virus?

FIV Antigen Tests are the primary screening test for cats. This test detects the viral antigens, which typically increase about 60 days post-exposure, but can take as long as 120 days. If your cat was in a fight, if you just adopted a new cat or found a stray cat you decided to care for, you should get this test done twice, about 60 days apart, to avoid missing a recent infection.

PCR testing is another testing option and it screens for viral RNA. This test has been improved and is now just about as accurate as the FIV Antigen tests.

Western Blot is another type of test that detects antibodies to FIV. However, this test is not as accurate as the antigen tests and cannot differentiate between true infection and a cat that was vaccinated for FIV.

Routine blood work may show low red blood cells, low white blood cells, low platelets, and high globulins. These are not diagnostic for FIV but can give your vet needed information that screening for FIV and Feline Leukemia Virus is necessary.

Is there a treatment for Feline Immunodeficiency Virus?

There are some antiviral and immunomodulation treatments available; however, they are not cures. Cats can have severe side effects to many antiviral drugs, so be sure to discuss the pros and cons with your vet. The goal of these medications is to reduce clinical symptoms and increase survival times.

The most common antiviral is Zidovudine, or AZT. It is given twice daily and is most helpful in cats that have severe oral inflammation (stomatitis) or are showing neurologic symptoms.

How can I protect my cat from Feline Immunodeficiency Virus?

There is a vaccine available for FIV, but it isn’t entirely effective. There are 2 main mutations of FIV in the U.S., and the vaccine only includes one of those. If you have a cat that is outdoors only, gets into fights, or lives with a housemate that has FIV, this is still a good vaccine to consider. It’s given as an initial 2 set series over a month, then once yearly thereafter. Remember, the vaccine can cause some of the FIV tests to be positive!

If your cat does test positive for FIV and the test has been confirmed, keep your kitty indoors only to deter the further spread of the virus in the community. This will also keep your FIV-positive cat safer and healthier since they won’t be exposed to other viruses and infections.

Read more:

Feline Leukemia Virus

What You Need to Know About Vaccinating Your Cat

Safety Considerations for Indoor and Outdoor Cats

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Published: 2/26/2021
Last updated: 3/15/2022

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