I dread broaching the subject of feline immunodeficiency virus (FIV) with the owners of sick cats. As its name suggests, FIV is closely related to HIV, the virus that causes AIDS in people. When clients make that connection, I invariably see an “Oh, Crap” expression cross their faces.
My first job under these circumstances is to offer up just about the only good news I have available regarding this disease. Despite the similarities between FIV and HIV, the former is not transmissible to people. Put bluntly, you cannot catch AIDS from your cat. Also, cats that are diagnosed with FIV but are not yet showing signs of illness can remain healthy and enjoy a normal life for an extended period of time … often years.
Now on to the bad news. Infection with feline immunodeficiency virus weakens and eventually destroys a cat’s immune system and invariably leads to death. Cats with advanced FIV infections are at high risk for potentially fatal bacterial, viral, and fungal infections and some types of cancer. Symptoms of FIV infection depend greatly on what secondary diseases develop but can include:
- oral inflammation
- loss of appetite
- weight loss
- neurologic disorders
The virus is transmitted primarily through bite wounds, so cats that go outside or live with infected housemates are at greatest risk. It can be transmitted through the placenta from an infected queen to her kittens as well. There is a small risk associated with sharing food bowls, mutual grooming, and other activities that could expose an uninfected cat to an infected cat’s saliva.
Testing for FIV can get a little complicated, primarily because of the possibility of false positive results. When a screening test comes up positive in a cat that appears healthy the results MUST be confirmed with another type of test (e.g., a Western Blot) that has a lower incidence of false positive results. I also leave this option open for the owners of cats that have symptoms consistent with FIV, but frankly, false positives are much less likely under these circumstances. We also need to take positive screening tests with a big grain of salt in kittens younger than six months of age. Some of these individuals carry antibodies picked up from their mother but did not acquire the infection from her. Finally, an FIV vaccine is available, and vaccinated cats will test positive on both screening tests and a Western Blot, but not on a polymerase chain reaction test.
Treatment for FIV is generally limited to protecting the cat from infectious diseases (keeping them indoors, addressing anything that develops quickly and aggressively, etc.) and supportive care (e.g., providing excellent nutrition). The anti-viral drugs that have proved so successful in keeping people infected with HIV healthy are unacceptably toxic and/or more or less ineffective in cats. Interferon is sometimes prescribed, but studies call into question its usefulness as well.
Preventing FIV infection is as simple as keeping cats indoors and testing new arrivals before they enter the home. When cats are at high risk for FIV (e.g., they live with an infected housemate or cannot adapt to an indoor-only lifestyle), the FIV vaccine is worth considering, even though it does not protect against all forms of the virus and will make the cat appear to be infected on many FIV tests.
Do I need to say it again? A positive result on a FIV screening test in a cat that appears to be healthy MUST be confirmed.
Dr. Jennifer Coates