Both feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) belong to the retrovirus family. Other than that they differ physically in many ways and in the diseases they cause. I do not know if the virus has become more common or if we are just more aware of it now. It is said to infect approximately 2.5% of the cats in the United States. Outdoor, unneutered male cats and all cats that fight over their territory are at particularly high risk of this disease. The virus is present in the saliva of infected cats and it is primarily passed through cat bites. So indoor cats are at much less risk as are single-cat households. Mother cats can pass this disease to their kittens. I have found that most of the apparently healthy kittens that are born to infected queens eventually test negative for the disease.
When cats are first exposed to this virus it enters certain white blood cells (the T-lymphocytes) that reside in the pet’s regional lymph glands. When this occurs subsequent to fighting, these are often the lymph nodes of the head and neck and groin. It then spreads throughout the entire lymphatic system. The pet’s owners do not usually notice this stage of the disease. Cats then enter a stage of low-grade fevers; low white blood cell counts (neutrophils and T-helper cells) and increased susceptibility to infections. Anemia may also develop. This stage of chronic malaise may last for years. It is in this stage, as the disease gradually worsens, that cats are likely to be presented to veterinarians. This is the period of immunodeficiency we are so familiar with because of the human AIDS virus. Cat FIV virus does not cause human AIDS and human beings cannot contract cat FIV/AIDS virus. In the immunocompromized stage of this disease body defenses are weakened. Now the cats become susceptible to diseases caused by common bacterial, protozoan and viral agents that exist all through our environment. It is only in weakened pets that these organisms pose a danger and they ,not the virus, cause the symptoms of FIV and the eventual death of the pet.
When these cats are presented to me they are often thin, scruffy and ill-kept. This is because they do not feel good. Their appetites are poor and they often have strong mouth odors and oral infections that limit eating. Their eyes and nose are often crusty and they may have upper respiratory tract, skin and ear infections. Unneutered female cats often miss their periods. These problems come and go between periods of relatively good health and correspond to periods when their white blood cell counts are very low.
I test any cat with these signs at my office with the Idexx FIV/FeLV SNAP test . With only three drops of blood, this test detects both the presence of antibody against the feline immunodeficiency virus or the presence of feline leukemia virus. Adult cats that once test positive to FIV generally remain positive throughout their lives. Immature cats often become negative for antibody over a three to five month period. These kittens never had the virus – only their mother’s antibody. A small percentage of cats will give a weakly positive, indecisive reading with the SNAPS test. When this occurs I send their blood off to a regional laboratory for more sophisticated FIV testing. Very early in the disease, the SNAPS test may give false negative results. That is why cats that are known to have been exposed to FIV should be tested twice at three-month intervals to be certain they are not incubating the disease.
This disease is the best reason there is to keep you cat indoors. Once a cat has the virus there are only limited treatments that I have. Antibiotics help control secondary bacterial infections and good nutrition prologs the cat’s periods of “good” health. Keeping the cat inside the house will eliminate fight wounds and abscesses. Cats that are not eating benefit from nutritional caloric pastes, intravenous fluids, vitamin injections and, in some instances, corticosteroid and anabolic steroids. Human AIDS drugs do not seem to help cats. They have too many side effects. There are some reports that interferon administration is helpful for a time.
The lifespan of feline FIV-positive cats varies greatly. Some will live for years with the virus. Others fade rapidly over a few months despite our attempts to delay the disease. Basically, the worse the cat looks, that is, the poorer its general health, the shorter it’s life span will be. The degree of immunosuppression dictates these cat’s general health. Laboratory tests are available that measure the ratio of two variants of lymphocytes, predicting the severity of immunosuppression (CD4/CD8 lymphocytes). However, the owners and veterinarian’s “gut feeling” is just as accurate in predicting the cat’s future.
The virus of feline immunodeficiency disease is quite fragile and is destroyed by most household cleaning agents. Drying and heat rapidly destroy it. An excellent disinfectant is ordinary generic household bleach diluted one part bleach in twenty parts water. For the bleach to be effective, heavy soiling should be removed first with detergent. Several days in bright sunshine will destroy the virus in porous objects, as will microwaving damp microwaveable objects. However, Cornell University recommends infected premises remain vacant of cats for thirty days. For the peace of mind of the owners, I vaccinate new cats arriving in a household that recently suffered a feline FIV loss.
Recently, Wyeth Laboratories’ Fort Dodge Division began marketing the first available feline FIV/AIDS vaccine, Fel-O-Vax FIV. This pioneering research was done at the University of Florida and UC, Davis. Fel-O-Vax successfully immunizes eighty-four percent of cats when it is given in three initial doses, at 8, 12 and 14 weeks of age and yearly thereafter. Eighty-four percent protection is not bad, but it means that almost two out of ten cats can still catch the disease. All cats should be FIV tested to be sure they do not have the disease before the vaccine is first administered. Once the vaccine is administered the cat may react positively to the SNAPS test for the rest of its life. The most common reaction after vaccination is pain at the injection site, fever and, at the most, a day or two of listlessness. Since the vaccine is new, we do not know its long-term side effects. If your cat does not go out of doors you may not wish to have it vaccinated for FIV until long-term effects become known.

My clients frequently ask me when is it time to euthanize a FLV-positive cat. It is a difficult question that is never the same in any two cases. I tell them let it be as long as the cat appears happy. Many of my client’s cats remain healthy for a long time when they are kept in a sheltered environment and provided with good nutrition and health care. But there are other factors to be considered. Long term use of antibiotics in a household member (your cat) produces races of bacteria immune to these antibiotics. If these bacteria should later infect you, the infections may be difficult to control. Cats with FIV often have unhealthy mouths. Should these cats bite you when you are attempting to hand feed them these bite wounds may become infected with bacteria. Keeping an FIV-positive cat in a multi-cat household also exposes the other family pets to the disease.

Newest Clinical Studies:

(I added the copy below when these articles first came out. However, no subsequent confirmation of these finding appeared over the next two years. So I am uncertain of the accuracy of the first reports.)

Recently, several studies have found that the administration of feline omega interferon prolonged the life of cats that were positive for FeLV and or FIV. One of these studies, SURVIVAL OF SYMPTOMATIC FELV OR FELV AND FIV POSITIVE CATS TREATED WITH A RECOMBINANT FELINE OMEGA INTERFERON by Mähl P, Maynard L, Karine De Mari K, and Lebreux B used this product (rFeIFNw) in very well controlled clinical studies. This study concentrated on chronic mouth infections which are common in positive cats. 28 cats were given 500,000 units of this interferon per pound body weight, once a day for 5 days and 20 cats received a placebo. Cats receiving omega interferon lived, on average, twice as long as cats that did not receive the product. The period these cats were studied was only a half year so we do not yet know the effects of repeated administrations. To my knowlege, this product, sold by the Virbac Co. is not yet available in the US but is in Japan and Europe (See Threads below).

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