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Feline immunodeficiency virus, also known as feline AIDS, was first discovered in 1986 in a California cattery. It occurs worldwide, but its prevalence depends on the locale and the population of cats tested. FIV is in the same family of retroviruses as FeLV (feline leukemia virus), but unlike FeLV, it is known as a lentivirus ("slow virus"). FIV is similar to HIV, the virus that causes acquired immunodeficiency syndrome (AIDS) in human beings. However, FIV infects only felines, based on current evidence.
In the United States, from 1.5% to 3% of healthy cats are infected with FIV, and up to 15% of sick cats brought to the veterinarian are positive. In Japan, for unknown reasons, it's as high as 44%.
FIV is more common in unneutered males and any cats that roam outdoors. Indoor cats are not as likely to be infected. Most FIV-positive cats have a history of territorial fighting and abscesses from bite wounds. FIV is spread through the saliva in bites. From the bite wound, the virus passes beneath the skin, infects cells, replicates, and spreads to new areas through the blood vessels and lymphatic system. Other than through bites, FIV can be spread through prolonged, intimate contact. However, FIV-positive cats with no signs of illness have a good chance of surviving.
A less common route of transmission is from an infected mother cat to her kittens. The kittens may be infected in the uterus, through drinking her infected milk, or as they are delivered. But some may not acquire the virus, depending on the strain of FIV and the health of the mother cat. It's also possible for an FIV-positive cat to have an FIV-negative litter; or even have some kittens with FIV and some without.
Another way for cats to become infected is through FIV-positive blood transfusions, although this risk is low because of the availability of FIV diagnostic tests.
Sexual transmission of FIV is possible, although the rate of transmission is not known at this time. Neutering at a young age will eliminate this possibility.
It is unusual although not impossible to transmit FIV through casual contact, such as by sharing food and water bowls or litter pans, through the air, or by mutual grooming. Some cases of uninfected cats becoming positive after living with FIV-positive cats for long periods have been discovered, but so far these cats have not become ill.
An FIV antibody diagnostic test is now available. The diagnosis of FIV is dependent on the results of this test, plus the history and clinical symptoms in the cat. The presence of the FIV antibody in the blood indicates that the cat is infected with FIV--probably for its lifetime--and can transmit the virus to other cats. A negative result may mean that the cat has had no exposure to FIV; or that it has, but detectable levels of the antibody have not yet appeared. Also, a false-positive or indeterminate diagnosis can sometimes result. In all these cases another test should be performed eight to twelve weeks after the first test to confirm the diagnosis.
In the case of FIV-positive kittens, results of testing may be positive for twelve to sixteen weeks after birth because of transfer of FIV antibodies from the mother. However, only a few of these kittens may become infected. Any kittens with positive results to antibody tests should be re-tested when they are by eight months of age to determine their FIV status.
Symptomatic FIV-positive cats can suffer from a variety of secondary infections and symptoms, including: chronic, unresponsive skin or ear infections and abscesses, poor coat condition, respiratory problems, severe weight loss, anemia, skin sores, abortion of kittens, loss of appetite, diarrhea, severe oral infections, periodontal disease, gum inflammation, sinus infections, poor healing, blood disorders, persistent mange, inflammation of the eye tissues, lymph gland enlargement, persistent fever, recurrent urinary tract infections, fungal diseases, toxoplasmosis, and brain disorders (i.e., may act demented, attack other animals or people, or have seizures). FIV-infected cats are also susceptible to cancers such as lymphoma.
The disease progresses slowly and erratically. Four to six weeks after a bite, swollen lymph glands, immune suppression, and fever may appear. Drops in white blood cell as well as red blood cell counts may develop. The cat may be fine for months or even years, but eventually stress will reactivate the disease. Infections that would normally be minor become serious because of the compromised immune system. Secondary infections are the major cause of death in FIV-positive cats. Death may come anywhere from six months to three years after the initial infection.
There is presently no cure and no vaccination for FIV. Many cats will remain in good health for months to years. Cats who have already had one or more severe illnesses due to FIV infection, or have persistent fevers or weight loss, will die sooner.
Recommendations for an FIV-positive cat are to keep it indoors, away from other cats. If a new cat is introduced into a multiple-cat household, it should be tested before coming into contact with FIV-negative cats. In a multiple-cat household where there is no fighting among the cats, transmission of FIV is rare. Therefore, even if there are infected cats in a multiple-cat household, unless fighting occurs, the risk to non-infected cats is minimal.
Standard treatment includes antimicrobial drugs administered for long periods to control bacterial and fungal infections. Intravenous fluids, blood transfusions, and feeding of high-calorie dietary supplements are also used. Corticosteroids or other ant-inflammatory drugs may be recommended to control gum and oral infections. Anabolic steroids can be given for weight loss. However, these drugs treat only the symptoms, not the virus itself. Human AIDS drugs have also been found useful, but they are expensive and not easily available, and the side effects tend to be greater in cats. Effective treatment for HIV infection is still being developed. Alternative veterinarians recommend such measures as a raw, fresh diet, vitamins, and homeopathy to treat symptoms and boost the immune system. They also caution against any vaccinations for the remainder of the cat's life, because they believe it will further weaken the already compromised immune system.
If your cat has recently died of FIV and you wish to adopt a new cat, some precautions should be taken. A waiting period is not required between cats, because feline immunodeficiency virus will not survive for more than a few hours in most environments, and transmission of FIV is primarily through bites. However, FIV-positive cats often have other infections that can be passed on to a new cat. Therefore, cleaning, vacuuming, and disinfecting the house, as well as replacing food and water dishes, bedding, litter pans and toys should be done. The new cat should also be vaccinated against other infections before entering the household.
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