Feline immunodeficiency virus is a retrovirus in the lentivirus subfamily. The primary mode of transmission is through bite wounds. Because neutered cats fight much less (if at all) than intact cats, transmission of FIV can be significantly reduced through neuter programs. It is possible, but less common, for an infected mother to pass the virus to her kittens before they are born or while they are nursing. It’s important to note that the virus typically does not spread through mutual grooming, sharing food and water bowls, or sharing a litter box.
Community cats and owned cats contract FIV at similarly low rates. According to one study, an estimated 2 to 4 percent of community cats carried the virus.
Most FIV-infected cats live many years—sometimes their entire lives—without any visible effects from the virus, so an FIV-positive diagnosis is not cause for alarm.
In cats who develop FIV-related disease, the virus can cause varying degrees of immune system dysfunction. This most often manifests as a reduced ability to fight infection. For example, an adult male cat with recurrent abscesses will take longer to heal than would be expected. Other types of infections caused by viruses, bacteria, and fungi may also become more serious and take longer to resolve.
How FIV Exposure Can Affect a Cat
After initial infection, the virus spreads to the cat’s lymph nodes, causing them to become enlarged. Fever can develop and last for several days. During the second stage of infection, the cat is often completely asymptomatic for many years. If disease develops, this will occur during the third stage.
The virus has a long incubation period, meaning that a cat who tests FIV-positive may live free of FIV-related disease for a lifetime.
In the third stage of the virus, the cat may develop signs of immunodeficiency and secondary conditions, such as opportunistic infections, cancer, kidney disease, or tumors. All of these conditions can occur in cats without FIV infection, so an association with FIV is often speculative.
FIV symptoms can also include:
- Loss of appetite
- Weight loss
- Poor coat condition
- Persistent fever
- Inflammation of the gums and mouth (gingivitis and stomatitis)
- Skin, urinary, and upper respiratory tract infections
- Persistent diarrhea
- Seizures, behavior changes, and other neurological disorders
- A variety of eye conditions and ocular inflammation
- Intestinal or urinary tract infections
FIV Testing Is Not Recommended for Community Cats
Alley Cat Allies does not support testing community cats for FIV. In addition to low rates of disease, low likelihood of transmission, and long lifespan, the cost of testing is substantial. We believe that funds are more effective when invested in neutering, rather than FIV testing.
Moreover, FIV test results can be false, inaccurate or inconclusive:
- Standard tests only detect antibodies against the virus, not the virus itself. The presence of antibodies does not mean the cat is infected.
- Positive FIV tests in kittens under 6 months of age should not be interpreted as FIV infection. Kittens are rarely infected but may test positive because antibodies can be passed from infected mothers through nursing. For a more accurate interpretation, FIV-positive kittens under 6 months of age should be retested between 8 and 12 months of age, when maternal antibodies have declined.
- Current FIV tests cannot distinguish between cats who are infected with FIV, vaccinated against FIV, or both infected and vaccinated. Fel-O-Vax® FIV vaccine, approved in 2002, stimulates the production of antibodies that are indistinguishable from those that develop from natural infection.
There is no cure for FIV. However, a cat who tests FIV-positive may live free of FIV-related disease for her lifetime. By carrying out spay and neuter programs, the risk of transmission will be greatly reduced.
 “Prevalence of feline leukemia virus infection and serum antibodies against feline immunodeficiency virus in unowned free-roaming cats,” JAVMA, Vol 220, No. 5, March 1, 2002