The diagnosis of FIV infection is confirmed by finding antibodies to the FIV virus in the cat's blood. This test can be done by your veterinarian. Any sick cat should be tested because of the association of FIV with chronic illness in the cat. Because apparently healthy cats may harbor FIV in a dormant state for many years, it is wise to also test new adult cats coming into a household and cats entering closed populations, especially catteries. There is no specific treatment for FIV infection.
Veterinarians treat the symptoms, such as infection or cancer, and give supportive care.
Unfortunately, the outlook for cats in the advanced stage of this disease is poor. Even if the signs of illness can be temporarily controlled, FIV infection is ultimately fatal to the cat. At this time there is no vaccine for preventing FIV infection. You can reduce the risk by neutering your cat to reduce roaming and territorial fighting behavior, and by keeping your cat indoors.