Feline Immunodeficiency Virus (FIV)

Feline immunodeficiency virus (FIV) is a type of virus called a retrovirus. It is in the same family as human immunodeficiency virus (HIV, the virus that causes AIDS).

It attacks the immune system and as a result, the cat is unable to fight off various infections and cancers. There is no evidence FIV can be transmitted to mammals other than cats.

Retroviruses are fragile, being easily inactivated by ultraviolet light, heat, detergents, and drying.

The overall prevalence of FIV in the healthy UK cat population is approximately 6 per cent and estimated to be approximately 14 per cent in the sick cat population.

How is it transmitted?

FIV is NOT transmitted by prolonged close contact, as is the case for FeLV. FIV is shed in the saliva and is transmitted by bite wounds.

For this reason entire male cats carry a higher risk of infection and a free-living lifestyle, of feral or stray cats, increases the prevalence.

Any cat can be infected at any age but there is often considerable delay between infection and development of clinical signs and thus the appearance of the disease is more common in middle-aged to elderly cats.

Clinical signs

  • The disease conditions associated with FIV infection are fairly non-specific. During the primary phase of infection in the first 2-4 months, cats may show short-term signs of illness including lethargy, high temperature and possibly lymph node enlargement.
cat paw

Did you know – cats can have a dominant paw, causing them to favour either their left or right paw when doing complicated tasks!

relaxing cat Marley

Marley having a relaxing time

  • Most cats will recover from this early phase and enter a second phase when they appear to be healthy.
  • Eventually in the third phase of infection, other signs of disease develop which can be as a direct effect of the virus. One example would be infection of the gastrointestinal tract which may cause diarrhoea. By depressing the immune system and the cat’s ability to fight off infection, the FIV infected cat is then prone to other secondary infections and diseases. Other signs seen include lethargy, weight loss, inappetence, pyrexia, swollen lymph glands and gingivitis (inflamed gums). These signs can all progress to seizures or fits as the nervous system becomes affected.

Treatment of FIV

Although FIV-positive cats can live for many years, your vet needs to know if your cat is FIV-infected to provide the best care e.g., proper vaccinations and aggressive treatment of infections.

Stress and exposure to ill animals should be avoided. FIV-positive cats should be kept indoors both to protect them from exposure to disease and also to prevent them from spreading FIV to other cats.


No vaccines are available against this disease. If one cat in a household is confirmed to be FIV positive then ideally the FIV infected cat should be isolated or rehomed.

However, as the risk of transmission by social contact such as sharing food bowls and mutual grooming is very low, many owners elect to keep the household as it is. It may be helpful to feed cats using separate food bowls as large amounts of virus are present in saliva.

Litter trays and food bowls should be disinfected after use to kill the virus. Once outside of the cat’s body the virus dies within a few minutes, so infection is not easily carried on clothing or other objects.

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