Feline immunodeficiency virus infection
Also called FIV, feline AIDS
A viral infection of cats, spread mainly by bites, that slowly weakens the immune system. Many infected cats stay healthy for years, and a positive cat should never be put down for that reason alone.
Cause and spread
- Cause
- Feline immunodeficiency virus, a lentivirus related to HIV. People cannot catch it.
- How it spreads
- Mainly through bite wounds between cats, so adult males and outdoor cats are most at risk. The virus survives only minutes outside the cat.
Signs to watch for
- Often none for years
- Weight loss and poor condition
- Repeated infections, mouth or gum disease
- Swollen lymph nodes
- Lymphoma in some cats
Many diseases look alike. Only a laboratory test can tell them apart, so please see a veterinarian for any sick animal.
How it is diagnosed
The usual screening tests detect antibodies to the virus. A negative result is reliable, but a cat that may have been infected recently should be re-tested 2 months later. Kittens under about 16 weeks can test positive from their mother's antibodies. PCR, which detects viral DNA, is used to confirm a doubtful positive result, a recently vaccinated cat or a kitten, but its results vary between tests, so it is read alongside the antibody test.
- Usually the first testFeline Retrovirus Panel (FeLV + FIV) (panel)Screens for FeLV and FIV together.
- Confirms the diseaseFeline Immunodeficiency Virus (FIV) PCRDetects the virus's DNA. Used to confirm a doubtful antibody test, or in kittens and recently vaccinated cats.
- Follow-up and monitoringComplete Blood Count (CBC)Part of regular health checks in an infected cat.
Prevention and control
- Keep cats indoors or limit outdoor access
- Test cats before introducing them to others and watch new introductions
- Neuter infected cats to reduce fighting and spread
- Give infected cats veterinary health checks at least every 6 months
Where this information comes from
- Feline Immunodeficiency Virus (ABCD guideline) · European Advisory Board on Cat Diseases (ABCD)
General information for animal owners and veterinarians, last checked October 2026. It does not replace the advice of your veterinarian, who should decide which tests and treatment your animal needs.