by Barry B. Burtis D.V.M.
Feline Immunodeficiency Virus and Feline Leukemia Virus
A recent Pet Tales column dealt with the risk of bite wound infections and abscesses that can develop after a cat is bitten by another cat. There are two other very significant feline viral diseases that are most easily and most commonly spread between cats as a result of bites they inflict on one another. Feline leukemia virus (FeLV) is the first of these viruses spread in this manner. The second one is another retrovirus that causes an immunodeficiency disease in domestic cats. It is called the feline immunodeficiency virus (FIV) and is in the same subfamily of viruses as the HIV virus, the causative agent of AIDS in humans. FIV is a cause of infection only in cats.
The feline leukemia virus can cause fatal illness in cats either by causing malignancy or by depressing the cat's ability to fight infection, leading to the development of secondary disease. It affects cats throughout the world. In North America it affects 2-3% of healthy cats. It seems to be slightly more prevalent in male cats, but there are no breeds that seem more at risk to become infected. It occurs most commonly in cats between 1 and 6 years of age. A cat that goes outdoors or a cat that lives in a multiple cat household has a significantly increased risk of infection. In addition to bites, cat-to-cat transmission can occur with casual contact (grooming) or by sharing dishes or litter pans. It can be spread from mother to kittens before birth or via the milk to nursing young.
The onset of FeLV associated disease usually occurs over a period of months to years after infection. Since there are many different diseases that an infected cat becomes more susceptible to, there are many different signs and symptoms that may develop in an infected cat. Lymphoma is the most common associated form of cancer. This cancer may affect lymph nodes, various internal organs, the eyes or the nervous system. Diseases that are non-cancerous may cause cats to exhibit chronic respiratory ailments, persistent diarrhea, mouth and gum inflammation, fever and non-responsive or recurrent skin or ear infections.
There are vaccinations that are quite effective against FeLV. Cats who are at risk to the disease should consider such protection. As with any vaccination, it is important that they be given prior to exposure to the virus.
Feline immunodeficiency virus and the problems that it can cause for cats are very similar to the FeLV. FIV is most often seen in free roaming male cats older than 6 years. In the United States and Canada, incidence of the disease is estimated at between 1 ½ to 3% of the healthy cat population and between 9 to 15% in cats with signs of clinical illness.
Cats that are infected with FIV, similar to people with HIV, have an acute stage of illness. With cats it begins 4-6 weeks after a bite from an infected cat. Most cats develop a fever, may seem depressed and often will have enlarged lymph nodes. This stage lasts a few weeks to months and the symptoms are usually so mild that the owner rarely notices them. After recovery from the acute stage, cats may appear completely normal for 3 years or more. During this time FIV is gradually destroying the immune system, reducing the cat's ability to fight infection. Once again, depending on the disease that results a great variety of symptoms of illness may be shown. Mouth, throat and gum problems, eye problems, persistent diarrhea, certain types of cancer, even sleep pattern or behaviour changes may be noticed. In cats with FIV who continue to get in fights with other cats they are likely to develop bite wounds or abscesses that fail to respond to usually successful treatments.
Veterinarians can diagnose the disease with the help of a blood test. Various treatment measures can be used to support cats that develop FIV associated diseases. Recurrent and chronic health problems that will require medical attention are likely in affected cats. It will be important to try and ensure they do not spread FIV to other cats. Unfortunately, at this time there is no effective vaccine against the virus. The best prevention is to avoid contact with FIV-positive cats and that means keeping your cat inside and out of harm's way.