Feline Immunodeficiency Virus

Immunodeficiency virus in cats

Feline immunodeficiency virus (FIV) is responsible for a fatal disease syndrome in cats that is similar to HIV infections in humans. For that reason it is often referred to as kitty AIDS, but it must be borne in mind that it is not contagious to humans or other animals. FIV infected cats are found worldwide, with estimates in healthy cats ranging from 1.5 to 3 percent in the United States. Like AIDS, cats can be FIV positive for years before showing any signs of clinical illness. Fortunately, it is not as easily spread as feline leukemia virus, nor is it as common. Although no cure exists, it does not present an automatic reason to euthanize cats in shelters. Appropriate adoptive homes may be found, and they can be held safely in the shelter until rehomed if certain precautions can be taken.


FIV is caused by a retrovirus (lentivirus) that is similar to HIV in that it breaks down the immune system’s ability to fight off disease. The virus does not persist in the environment outside the cat’s body for more than a few hours and is readily destroyed by most disinfectants, which is good news for shelters that decide to hold FIV positive cats.


It is transmitted primarily through bite wounds, and is much more common amongst intact male cats who are most likely to fight. Casual cat-to-cat spread is not believed to be common. It may also be transmitted from mothers to kittens. Although the virus is found in blood, saliva and cerebrospinal fluid, as stated before, it is fragile and does not survive outside the body for very long. For this reason, cats may be safely housed individually without endangering the lives of other cats in the shelter. There is also no reason to recommend a waiting period before adopting a cat into a household that previously housed an FIV positive cat as long as common sense cleaning measures are taken.


Because the virus affects the immune system’s ability to fight disease, viruses, bacteria, protozoa and other disease organisms can cause severe illness. FIV positive cats that are kept in shelters are at additional risk for contracting other diseases because of the stress associated with shelter life and the increased exposure to infectious agents.

The white blood cell count drops 4-6 weeks after infection, which is when signs will begin to appear. This is the initial acute phase, wherein signs may start out very vaguely, with anemia, a poor hair coat, appetite loss, swollen lymph nodes and fever. They often recover from this phase. The second phase may last for years, during which time the cat often appears to be normal. It must be borne in mind that although they may have periods of normal health alternating with illness, infection is lifelong. Dental problems, inflammation of the gums (gingivitis) and mouth (stomatitis) are very common, along with other infections of the urinary bladder, skin and upper respiratory tract appearing. Diarrhea and/or progressive weight loss may also present problems. If the virus affects various other organ systems, cancer and blood diseases, seizures, behavior problems and other neurological and ocular abnormalities may be seen. Eventually the cat will succumb from the progressive destruction of white blood cells and the collapse of the immune system.

Diagnostic Testing

The American Association of Feline Practitioners (AAFP) recommends that the FIV status of every cat should be known. Detailed information about test procedures, interpretation and guidelines for caring for FIV positive cats may be found on their website www.aafponline.org. According to their guidelines, it is important to remember that no test is 100% accurate at all times and under all conditions, and that a confirmed positive test result is an indication of retro virus infection, not clinical disease. Although these guidelines were not developed primarily for shelters, it must be held as a general principle that no healthy cat should be euthanized based on the results of a single positive test. Other considerations:

  • The screening test for FIV commonly used in shelters is an ELISA test that detects the presence of antibodies to the virus, unlike the test for feline leukemia that looks for the presence of the virus (antigen). It is available in a FeLV/FIV combo testing kit.

  • Queens and each member of a litter should be individually tested.

  • Any healthy cat that tests positive should be retested with the Western Blot test, which is considered confirmatory.

  • Infected mother cats can pass their antibodies to their kittens, so kittens that are tested before 6 months of age may actually test falsely positive until their mother’s antibodies are eliminated from their bodies at around 6 months of age. So unlike the feline leukemia test that can be performed at any age, FIV testing that is performed before 6 months of age should be repeated at 60 day intervals if a positive result is obtained.

  • It may take 8-12 weeks after a FIV exposure to produce detectable levels of antibodies, so it would be prudent to wait at least 60 days before testing exposed cats.

  • Cats that are very debilitated may be unable to produce any antibodies, which would also yield a negative test result although the cat has the disease.

Bear in mind that once infected, cats rarely, if ever, eliminate the infection.

Treatment and Management

There is no cure for FIV and treatment in the shelter environment is not recommended.

Management in shelters

If a decision is made to house or adopt FIV positive cats, several precautions should be observed both while in the shelter and in the new home. Cats should be housed individually or in stable colonies in which fighting does not occur, as cat bites are the main mode of transmission. They should not be housed with FeLV positive cats. Extra sanitation measures should be observed, such as more frequent hand washing and disinfection, with staff wearing disposable aprons and utilizing disposable rags, towels etc when cleaning areas housing these animals. Stress should be minimized.

Advice for adopters

Adopters should be fully informed about FIV and the risks the infection may pose to other cats in the household. Adopters must be advised that FIV positive cats should be confined indoors both to prevent spreading the disease and exposure to other animals that may be carrying infectious disease. Healthy FIV positive cats should be vaccinated with the core vaccines (FVRCP and Rabies), dewormed and neutered. They must be fed a nutritionally complete feline diet, and hunting, raw foods or unpasteurized milk should be avoided. Routine semi-annual visits to the veterinarian should be scheduled, paying particular attention to oral health. Any illnesses or abnormalities should be reported to the veterinarian promptly, remembering that response to therapy may take longer, which is normal. The adopter may also be advised to weigh the cat regularly since weight loss may be one of the first signs of a problem.

There is a new FIV vaccine available. Unfortunately it interferes with disease testing and is not recommended for use in shelters. If used however, cats should be tested beforehand, and positive cats should not be vaccinated with it.

© 2004 ASPCA

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