Feline Immunodeficiency Virus Infection

Feline immunodeficiency virus (FIV) is strikingly similar to the human immunodeficiency virus (HIV) that causes AIDS. FIV is found in most parts of the world and studies have found antibodies against the virus from serum samples dating to the late 1960’s. The virus is present in the saliva and infected cats spread the disease by biting. FIV does not spread to kittens while they are in the uterus but, rather, through the milk when they begin to nurse. Not every kitten in the litter will become infected. Although any cat may become infected, FIV is most common in male free-roaming cats that fight.

Infection with the FIV virus is divided into three stages: acute, subclinical, and the chronic clinical stage. The acute stage lasts 3 to 6 months and is characterized by mild illness. Intermittent short episodes of lethargy, decreased appetite, and fever are typical. Often this stage goes unnoticed.

The subclinical stage lasts from months to years. Affected cats appear healthy but their immune system continues to deteriorate. In the chronic clinical stage, the deterioration of the immune system predisposes infected cats to a variety of disorders. Chronic mouth infections, respiratory infections, intestinal disease, fungal diseases, eye diseases, diseases of the nervous system, cancers, and leukemia are common. Near the end of the disease, many cats develop a wasting syndrome and lose 20% to 30% of their body weight over a period of several weeks. With FIV infection, the average time from diagnosis to death is 5 years.