What is Feline Immunodeficiency Virus (FIV)?

In humans, HIV, or the human immunodeficiency virus, is known to cause AIDS, or the acquired immunodeficiency syndrome. Similarly, in cats, FIV, or the feline immunodeficiency virus, can cause a condition known as Feline AIDS. While the retroviruses HIV and FIV are in the same family and work in similar ways, humans cant catch FIV, and cats cannot catch HIV the viruses are species specific. Like HIV, FIV attacks the immune system, leaving an infected cat vulnerable to a number of infections and cancers. The only risk to humans is from the secondary infections a cat may have because she is FIV positive.

FIV is contagious to other cats. Unlike the Feline Leukemia Virus, which is generally transmitted during social behaviors such as mutual grooming, FIV is usually spread through aggressive behavior, such as when one cat bites another cat and the virus is transmitted in its saliva. About 2% or 3% of cats in the United States are believed to have FIV, which affects both domestic and wild cats. FIV infections are more common among outdoor feral cats, which fight more frequently. In addition, female cats are half as likely to be infected as male cats.

However, if a mother cat becomes infected with FIV during pregnancy or while nursing her kittens, she may transmit FIV to her kittens, although this is very rare. Generally, if a mother cat is infected with FIV, her kittens wont be born with FIV, although they may test positive for the FIV antibodies that their mother passes along to them. Kittens with an FIV positive mother can test positive for up to twelve weeks after they are born, as FIV testing looks for the presence of antibodies to the virus rather than the actual virus itself. Similarly, cats that have previously been vaccinated for FIV will also test positive because they will have FIV antibodies in their blood.

As with HIV, FIV attacks the immune system. Initial stages of the infection may involve fever, a susceptibility to digestive or skin infections and swollen lymph glands. After this initial stage passes, the disease presents no outward signs as it slowly destroys the cat's immune system. Finally, an AIDS-like stage emerges, when the cat falls ill with bacterial or fungal infections or cant fight off the damage done by parasites. Some cats also develop cancers, again because their immune system is not functioning normally. FIV is ultimately fatal to cats.

A vaccine for FIV was developed in 2002, although feelings about the vaccine vary among pet owners. On the one hand, some owners are happy to have a way to help prevent this disease, but on the other hand, some cats develop a particular type of cancer known as a sarcoma at the vaccine injection site. Another concern is that any cat who is vaccinated against the disease will test positive for the disease if a cat is lost and is determined to be FIV positive when found, theres a reasonable chance that it may be destroyed. Further, the disease only affects, at most, 3% of cats in the United States, and the vaccine doesnt provide complete protection. Therefore, whether or not to administer the vaccine is a decision that an individual pet owner should make in partnership with their veterinarian.