Feline Immunodeficiency Virus (FIV)

David, our FIV positive cat

David, our 14 year old FIV positive cat

If you've had a cat test positive for FIV, the first thing to know is that it isn't necessarily a death sentence. FIV positive cats can often live long, relatively healthy, happy lives. For example, the cat in the above photo - David - is 14 years old and has had FIV for several years now. He was taken in as a stray and so we don't know for sure when he got it, but it has been at least seven years and he is still doing fine.

According to my veterinarian it isn't always necessary to keep an FIV infected cat separate from other household cats that are FIV negative. That is, unless there is a chance that your cats may fight and bite each other. We chose to house David separately just in case...

How is FIV Transmitted?

The most common method of transmission of feline immunodeficiency virus (FIV) is through a bite wound because the virus is shed in cat saliva. However, sharing food bowls doesn't seem to be a route a transmission - cats don't usually get FIV unless they are bitten by an FIV infected cat.

FIV is species specific, meaning that people and other animals can't get it. FIV only infects cats.

FIV Disease Progression

FIV belongs to the family Retroviridae. FIV is a retrovirus that consists of a single strand of RNA and the enzyme reverse transcriptase.

Once the virus enters a cat's body it enters the cat's cells where it releases the RNA strand and the enzyme into the cytoplasm. The virus then uses the host cells own machinery to create a DNA strand of the virus. This strand travels to the cell nucleus and the viral genetic material is inserted into the cat's genome where it remains. It often remains dormant for a period of time, but can replicate more of the virus at any time.

Once a cat is infected, FIV has a similar progression to human immunodeficiency virus (HIV). This is why FIV is sometimes called feline AIDS or cat AIDS.

FIV causes enlarged lymph nodes, which is primarily where the virus replicates. It can also cause low red and white blood cell counts.

An FIV infected cat can often remain healthy, sometimes for years. However, eventually, the number of T helper lymphocytes (CD4+ T cells) declines. These are specialized lymphocytes that assist other cells in the body in destroying pathogens, such as viruses and bacteria. When the number of T helper lymphocytes drops, then bacteria, fungi, and other pathogens are able to invade the body because the cat's immune system is compromised.

Common symptoms of FIV infection are chronic upper respiratory infections, bladder infections, gingivitis, fever, diarrhea, ear, and eye infections. In the later stages your cat may suffer from severe weight loss.

How is FIV Diagnosed?

Your veterinarian can test your cat for FIV using the ELISA (enzyme-linked immunosorbent assay) test. To do this your veterinarian will need to draw a small blood sample from your cat. The results are usually ready in about 10-15 minutes. Usually, this test is performed as a feline leukemia/FIV combo. Because the symptoms of FIV and feline leukemia are often similar this test can rule out both of them.

Keep in mind that a cat that has been recently infected with the FIV virus can test negative for the virus despite being infected. This is because there is about a three month incubation period before the virus is detectable in the cat's body.

If your cat test positive for either virus you should have a second test done to confirm the results before any decisions regarding the cat are made. It is uncommon, but false positives have been known to occur. If your cat test positive for FIV there are two available confirmatory tests: the IFA (immunofluorescence assay) and the Western Blot analysis.

Unlike the feline leukemia test, which tests for the presence of the viral antigen, the test for FIV tests for the presence of FIV antibodies. This means that a cat that has been exposed to the virus can test positive for FIV, but not be infected. This is especially important when testing kittens. Kittens whose mother had FIV may or may not be infected. However, because of the maternally derived antibodies through their mother's milk, the kittens will test positive for FIV, but may not have the virus. Kittens should be retested after several months to determine their true FIV status.

Treatment of FIV

Cats infected with FIV can live relatively healthy lives for several years. There is no reason to have them euthanized unless they become very ill. The cat may come down with frequent infections, but these can usually be treated with antibiotics or other medications obtained from your veterinarian.

I recently took in a stray that tested positive for FIV. Because I have other cats I do keep him in a separate room away from the healthy cats, but he is doing fine. I keep him separate because he was a stray and used to fighting with other cats outdoors. I keep him separate from my cats because I don't want to take the chance that he may fight with my other cats and infect them.

The thing to remember is that if your cat does test positive for FIV this isn't a death sentence.

In fact, many FIV positive cats can live normal to almost normal life spans with FIV.

There is no known cure for FIV, however, giving your cat interferon may help boost your cat's immune system. Interferon is inexpensive and can be obtained from your veterinarian. Other drugs that may help are acemannan and immunoregulin.

Some veterinarians recommend giving the cat anabolic steroids to help prevent severe weight loss and wasting.

FIV Prevention

The best way to prevent your cat from getting FIV is to keep it indoors and away from other FIV-infected cats. If you do let your cat outdoors then make sure it has been spayed or neutered. Cats that haven't been spayed or neutered are more likely to get FIV and other diseases because they are more likely to be involved in cat fights. Because of the risk of being bitten during cat fights, male cats that haven't been neutered are especially at risk of FIV infection.

Thankfully, FIV isn't all that common. Less than 3% of cats in the United States are infected with the virus.

Recently an FIV vaccine has become available. It uses killed FIV virus to promote antibody production against the virus.

The vaccine isn't 100% effective against the virus, plus there are some risks associated with the vaccine. You should talk to your veterinarian to determine whether or not your cat should be vaccinated against FIV. Vaccinations carry risks of their own that can sometimes be worse than FIV, such as vaccine induced sarcomas.

Keep in mind that if you get your cat vaccinated against the virus, he or she will then test positive for FIV because the test for FIV tests for the presence of antibodies. This means that if your cat gets lost and someone has it tested for FIV, that it will test positive, even though it is probably negative, and he or she could potentially be destroyed.