Feline immunodeficiency virus (FIV) is a major cause of illness and death in cats. The virus can infect any cat. It is spread by close contact (most often via bite wounds) and from mother to kittens across the placenta. It may also be spread by blood transfusions or by equipment that is contaminated with infected blood or other body fluids.
Fortunately the virus is susceptible to drying, sunlight, disinfectants, and detergents, and it does not survive well in the environment. It can sometimes persist long enough in shared food and water bowls, litter boxes and on other items to be transmitted to other cats.
FIV can cause a permanent infection that eventually leads to diminished function of the immune system and various associated clinical conditions. Frustratingly the symptoms can be extremely variable. Fever, enlarged lymph nodes (glands), and lethargy may occur soon after infection, but are often so mild that they are not noticed. Cats then enter a prolonged asymptomatic phase of infection that could last from months to years. Eventually cats progress to the point where they are severely immune deficient, and during this point secondary infections and other conditions may be seen.
Signs that may occur include intermittent fever, lethargy, and infections of the mouth (gingivitis and stomatitis). Neurologic signs, such as wobbly gait (ataxia), altered mental awareness, and seizures (rare) may be seen. Inflammation in the eyes (uveitis) and various cancers may develop. When a sick cat is diagnosed with FIV infection, it may be difficult to determine whether the presenting problem is caused by FIV or by some other disease.
Because cats can be asymptomatic shedders of virus and transmit the infection to other cats, it is recommended that cats be tested for FIV at some point in their lives. We often recommend testing kittens at the time of their spay and neuter. Testing may also occur when cats are acquired as a new pet; when they are exposed to an infected cat; when they are potentially exposed after escaping from the house or being allowed to roam outside; or when they are ill.
Diagnosis of FIV infection is made from a blood test that is available in our clinic. Initial FIV test positives may then be verified by tests that are done at outside laboratories. Verification is done not only by performing more than one type of test but also by testing the cat at different times.
Unfortunately there is no treatment proven to eliminate FIV infection. Some antiviral drugs and immune-modulating drugs have been tried, but no treatment is curative. Healthy FIV-positive cats do not require any specific treatment. Cats that are FIV-positive and have clinical signs are treated with appropriate medications and supportive care for those signs.
Cats with FIV infection should be kept indoors and isolated from non-infected cats, which can be difficult in multiple cat households. The American Association of Feline Practitioners recommends that healthy FIV-infected cats visit a veterinarian at least twice a year for a complete physical examination and that a complete blood count, biochemistry panel, and urinalysis be done at least once a year.
FIV-positive cats do not benefit from vaccination for FIV; however, they may receive other routine feline vaccinations (for feline rhinotracheitis, calcivirus, and panleukopenia virus, as well as rabies) as long as they remain healthy.
Cats with FIV infection may have a normal, healthy life for many years. In the later stages of infection (when the cat is immune-compromised and has a variety of secondary conditions), prognosis is guarded (uncertain) to poor.