Cat Feline Leukaemia Virus: Prevention, Welfare Impact, and Management

Feline leukaemia virus (FeLV) is a retrovirus that causes immunosuppression, anaemia, and cancer in cats, for which vaccination and management of exposure risk are the primary welfare interventions.

Key Facts

FeLV is transmitted through saliva, nasal secretions, and other body fluids — primarily through close contact and mutual grooming.
Outdoor cats and those in multi-cat households are at highest risk of FeLV infection.
Approximately 2-3% of cats in the general population are FeLV-positive, with higher rates in high-risk groups.
Persistently infected cats develop progressive immunosuppression, haematological disorders, and lymphoma.
The FeLV vaccine is classified as non-core but recommended for cats with outdoor access or multi-cat exposure.
Cats that test positive on initial screening should be re-tested 12 weeks later — some cats clear the virus.
Positive cats can live quality lives for months to years with appropriate supportive care and management.

Welfare Considerations

FeLV causes progressive welfare deterioration — immunosuppression leads to recurrent infections, anaemia causes lethargy and breathlessness, and eventual lymphoma brings its own welfare burden. Many FeLV-positive cats are euthanised prematurely due to owner anxiety rather than actual welfare impairment. Positive cats can live good lives for extended periods with appropriate management including keeping them indoors to prevent secondary infections and transmission to other cats, regular monitoring, and prompt treatment of secondary conditions. The welfare imperative is to make management decisions based on the individual cat's current quality of life rather than on diagnosis alone.

What You Can Do

Vaccinate cats with outdoor access against FeLV, particularly before multi-cat household introduction.
Test all cats for FeLV before introducing them to multi-cat households.
Do not immediately euthanise FeLV-positive cats without veterinary assessment of their current welfare status.
Manage FeLV-positive cats as indoor-only animals to prevent transmission and secondary infection exposure.