Feline leukaemia virus infection
Also called FeLV
A viral infection of cats that can suppress the bone marrow and immune system and cause lymphoma. Many infected cats stay well for years, but life expectancy is reduced.
Cause and spread
- Cause
- Feline leukaemia virus, a retrovirus that can integrate into the cat's own DNA.
- How it spreads
- Mainly in saliva of infected cats: through grooming, bites and shared food and water bowls. It can also pass from mother to kittens, and by blood transfusion. Kittens are most likely to develop lasting infection.
Signs to watch for
- Often no signs for months or years
- Anaemia and pale gums
- Lymphoma and other cancers
- Repeated or long-lasting infections
- Chronic gum and mouth inflammation
- Low white cell or platelet counts
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
Rapid tests detect the virus protein (p27 antigen) and are the usual first test, and they are repeated after about 6 weeks. They find cats with active infection but can miss cats whose infection has become hidden. PCR detects the virus's DNA in blood cells and finds more infected cats, so it is useful to confirm a doubtful result and to test blood donors.
- Usually the first testFeline Retrovirus Panel (FeLV + FIV) (panel)Screens for FeLV and FIV together.
- Confirms the diseaseFeline Leukaemia Virus (FeLV) PCRDetects the virus's DNA. Finds infection that antigen tests can miss.
- Supports the diagnosisComplete Blood Count (CBC)Shows anaemia and low blood cell counts.
- Supports the diagnosisFine Needle Aspiration Cytology (FNAC)Checks swollen glands or lumps for lymphoma.
Prevention and control
- Test every cat for FeLV, especially new, sick and rescued cats, and re-test 6 weeks later
- Vaccinate cats at risk: first dose at 8 to 9 weeks and second at 12 weeks, after a negative test
- Keep infected cats indoors, away from uninfected cats
- Test blood donors for the virus in their DNA, not only the antigen
Where this information comes from
- Feline Leukaemia Virus Infection (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.