First published in March/April 2006 Edition
FIV (feline immunodeficiency virus) is classified as a “lentivirus” or slow virus and is structurally similar to HIV (human immunodeficiency virus) causing a disease in cats similar to AIDS in humans. Lentivirinae are characterised by a very long incubation period followed by a slow onset of the disease.
Like HIV in humans, FIV is associated with a slow destruction of the body’s immune system; the white blood cells are depleted and this eventually causes an infected cat to be vulnerable to other infections that would not normally be a problem in a healthy individual.
FIV is widespread in the cat population throughout the world; the virus has been isolated in all the countries where veterinary researchers have looked for it. A similar virus also occurs in big cats, including puma, cheetah and African lions. FIV exists in many different strains and, like HIV, has a capacity to mutate, factors that have made the production of an effective vaccine problematic, although one is now available in the United States that protects against some of the strains prevalent there.
Epidemiological studies have suggested that around 8-10% of the healthy UK cat population and 15-20% of the sick UK cat population are infected with FIV. However, since many cat owners do not have their cats routinely tested for FIV and, given that exact numbers of ownerless stray and feral cats are unknown, the number of FIV-positive cats may well be much higher than these figures. FIV is most commonly found in middle-aged to older cats. Free-roaming unneutered male cats, especially aggressive ones that fight, are the most frequently infected, while cats housed exclusively indoors are much less likely to be infected.
FIV is species specific and poses no threat to humans and other animals. The virus was first isolated in 1986 by Dr Niels Pederson and Dr Janet Jamanoto at the University of California after someone running a cat rescue facility in Davis noticed that several cats in her care were exhibiting persistent symptoms that were similar to people infected with HIV. From stored blood samples, it is now known that FIV has existed in the cat population since at least the late 1960s but the likelihood is that it has been around and causing feline disease for much longer.
The presence of FIV infection in a cat impacts not only on its own health but on the health of all the cats with which it comes into contact. Veterinary experts recommend that the FIV status of all cats should be known in an effort to control the incidence of the disease in the feline population. However, given that numbers of unwanted, abandoned, stray and feral cats – those at highest risk of FIV infection and least likely to receive veterinary care – have reached pandemic proportions around the world, this recommendation will most likely remain utopian.