Last Updated on April 11, 2026 by admin
Feline Immunodeficiency Virus (FIV) is a retrovirus that attacks a cat’s immune system, gradually reducing its ability to fight infections. Like HIV in humans, FIV targets white blood cells essential for immune function. Cats infected with FIV may appear entirely healthy for years before immune deficiency becomes clinically apparent — but once it does, managing the condition becomes a long-term commitment.
How FIV Spreads
The primary route of FIV transmission is through bite wounds. When an infected cat bites deeply enough to draw blood, the virus in saliva is transferred to the other cat. This makes fighting — particularly the deep puncture bites that occur during territorial or mating conflicts — the dominant transmission pathway. Casual contact like grooming, sharing food bowls, or using the same litter box is not a significant transmission risk.
FIV-positive mother cats can transmit the virus to kittens, primarily in utero or through milk, though this is less common than bite-wound transmission. Kittens born to FIV-positive mothers will test positive for FIV antibodies for the first several months of life due to maternal antibodies — this doesn’t mean they’re infected. Retesting after six months of age gives a more accurate result.
Intact male cats that roam outdoors and fight have the highest risk of FIV infection. Neutering reduces both roaming and fighting behavior, and keeping cats indoors eliminates most exposure risk entirely.
Signs and Symptoms
In the early stages after infection, cats may show a brief period of fever, swollen lymph nodes, and general malaise. This often goes unnoticed or is mistaken for a minor illness. After this initial phase, many cats enter a prolonged asymptomatic period that can last years.
As the immune system weakens over time, symptoms become more pronounced. Recurrent infections — particularly of the mouth and gums (stomatitis, gingivitis), respiratory tract, and skin — are common. Persistent or recurring fever, weight loss, and deteriorating coat condition are other hallmarks of advancing FIV. In later stages, some cats develop neurological symptoms affecting coordination and behavior, and chronic diarrhea may be present.
Because these symptoms overlap substantially with other diseases, a veterinary diagnosis is essential. Behavioral changes and recurring infections in any cat should prompt a vet visit — FIV can masquerade as many other conditions.
Diagnosis and Testing
FIV diagnosis typically begins with an ELISA (enzyme-linked immunosorbent assay) blood test, which detects antibodies the cat’s immune system has produced in response to FIV. This test is often run as part of a routine in-clinic panel and can produce results quickly. However, ELISA tests can yield false positives, so a positive result is generally confirmed with a Western Blot test, which analyzes proteins specific to the virus and is more definitive.
PCR testing, which detects actual viral DNA rather than antibodies, is particularly useful in two situations: for kittens under six months old (where maternal antibodies can cause false positives on antibody tests) and in cases where clinical suspicion is high but antibody tests are negative. A positive PCR confirms active infection.
False positives can also occur in cats that were previously vaccinated for FIV (a vaccine that was available in the past but has been discontinued in the U.S.). A cat’s full history, including any prior vaccinations, should always be considered alongside test results.
Treatment and Management
There is no cure for FIV. Treatment focuses on managing the consequences of immune deficiency — controlling secondary infections as they arise, supporting overall health, and reducing stress on the immune system.
FIV-positive cats benefit from more frequent veterinary check-ups, typically every six months rather than annually, to catch problems early. Dental disease is particularly common and should be monitored closely; stomatitis can significantly affect quality of life and may require intervention. Parasite control is important, as FIV-positive cats are more vulnerable to the effects of intestinal parasites, fleas, and ticks.
Antiviral medications such as zidovudine (AZT) have been used in cats with FIV, but their use is limited by potential side effects including anemia, and their benefit in practice is variable. They are not routinely used except in specific clinical situations under veterinary guidance. Immunomodulatory treatments (such as interferon) are sometimes prescribed but have a limited evidence base.
Diet matters. High-quality nutrition supports immune function, and FIV-positive cats should be fed a balanced, nutritionally complete diet. Raw food diets are generally not recommended for immunocompromised cats due to the risk of foodborne pathogens.
Living with an FIV-Positive Cat
Keeping an FIV-positive cat indoors serves two purposes: it protects the cat from exposure to pathogens its immune system may struggle to handle, and it prevents transmission of the virus to other cats in the neighborhood. In multi-cat households, FIV-positive cats can generally coexist peacefully with FIV-negative cats as long as the cats get along well — casual contact doesn’t transmit the virus. Cats that fight, however, should be kept separated.
A stable, low-stress environment genuinely helps. Chronic stress suppresses immune function, and FIV-positive cats benefit from predictable routines, a calm household, and adequate resources (food stations, litter boxes, resting spots) to avoid conflict with other pets.
Prognosis and Life Expectancy
Many FIV-positive cats live for years after diagnosis without serious health consequences, particularly if they were diagnosed during the asymptomatic phase and receive consistent veterinary care. Some infected cats live a normal lifespan. The prognosis depends substantially on how advanced the immune compromise is at the time of diagnosis, whether secondary conditions are identified and managed promptly, and the overall quality of care.
A diagnosis of FIV is not a death sentence. Owners who understand what the diagnosis means — a need for attentive, proactive veterinary care and a few management adjustments — typically find that their cats continue to live comfortable, good-quality lives for a long time.
Prevention
Because there is currently no FIV vaccine available in the United States, prevention depends on reducing exposure. Neutering cats reduces fighting and roaming. Keeping cats indoors eliminates the primary risk pathway. All newly adopted cats should be tested for FIV before being introduced to a household with other cats, and any cat with a bite wound should be seen by a vet and retested for FIV after the appropriate window period.