As its name suggests, Feline Immunodeficiency Virus (FIV) is closely related to the Human Immunodeficiency Virus (HIV) responsible for causing AIDS in people. There is no cure for either disease and the virus causes the gradual destruction of the white blood cells needed to protect the body against infectious diseases. However, the two viruses will only survive inside normal host species – in other words, there is no risk of humans catching FIV from a cat, or vice versa.
FIV is found in the saliva and other bodily fluids of the cat and passes from cat to cat through bites. It occurs more frequently in un-neutered tomcats than in neutered males and is found most often in strays. Female cats are generally less likely to get involved in fights than males. However, a single bite may be enough to transmit infection and once it is there a cat is incapable of getting rid of the virus.
The virus will also pass between generations; about one in four kittens born to an infected female carries the virus. Infection may pass from mother to kittens during pregnancy (through the placenta) or as a result of the mother licking her offspring or biting the birth cord when they are born. Unlike HIV, there is no evidence that FIV is sexually transmitted.
In the first few days after it is infected your cat may show signs of ill health, such as a slight fever but it is unlikely that you would notice these minor changes. A cat that is already infected with the Feline Leukaemia Virus (FeLV) may show more severe symptoms. However, they soon appear to get better and may then be perfectly healthy for months or even years.
Eventually they will become more susceptible to infection, with effects which vary considerably between different animals such as lethargy, swollen glands, a dull coat, fever, and weight loss. Affected cats often develop inflammation of the mouth, discharging and inflammed eyes, anaemia and diarrhoea.
Certain forms of cancer seem to be more common in FIV-infected cats and in a few cats the nervous system is affected, causing behavioural changes, convulsions, dementia etc.
FIV is more common in areas where there are large numbers of un-neutered male cats. Up to six in every 100 healthy cats carry the virus but it is much more common in ill cats – up to one in six ill cats have the virus. Because there is a long gap between infection and signs showing, the disease is most commonly seen in cats between six and ten years old.
Until a cat starts to suffer from a series of infections, as a result of its failing immune system, there is usually no reason to suspect that it is infected with FIV. A blood test has been developed to detect antibodies to the virus in apparently healthy animals. However, the test is not effective for several weeks after infection because infection is not detectable for that length of time. In a small proportion of infected cats, perhaps one in ten, antibodies will never appear. A more complicated test, which test for the virus itself can be used to check the results of the first test.
As there is no cure, your cat is eventually likely to die from an infection which would not be serious for a normal, healthy animal. Your vet may be able to give your cat some treatment to help counter these infections initially.
In the future it may be possible to treat FIV with the antiviral drugs being developed against the human disease. Trials have shown that the drugs provide short-term improvements in some cats but they are expensive and are not yet routinely available. A vaccine (Fel-O-Vax FIV from Fort Dodge) has recently been licensed in the United States but is not available in Europe.
Making sure that your cat’s vaccinations against other diseases are up to date you can reduce the risk of it catching these diseases.
Cats that live in small groups are less likely to fight and pass on the infection in a bite. However, if you have an infected cat who lives with other healthy cats you may decide that it is safer to keep them apart. Having an infected tom cat neutered may reduce the risk of him passing the disease to his housemates. Female cats with the virus should be spayed to prevent the virus being passed to their kittens.
If your cat dies as a result of FIV you may want to get a new cat. As long as all the other cats in the home are healthy there is no significant risk to the new arrival. The virus quickly dies once it is exposed to the air and the new cat is unlikely to be infected from using the same feed bowl or litter tray as its predecessor.