Cat Feline Leukaemia Virus and Welfare

FeLV is a retrovirus causing immune suppression, anaemia, and cancer in cats — vaccination and testing prevent spread and allow management that maintains quality of life.

Key Facts

Feline leukaemia virus (FeLV) is the most common infectious cause of cancer in cats and causes fatal immune suppression.
FeLV is transmitted through prolonged close contact including mutual grooming, shared food bowls, and biting.
Approximately 2-3% of cats in multi-cat households test positive, with higher rates in stray populations.
Vaccination is highly effective and is considered core for cats with outdoor access or in multi-cat households.
FeLV-positive cats can live well for months to years with appropriate management and monitoring for secondary disease.

Welfare Considerations

FeLV causes a welfare trajectory that begins with immune suppression and ends in cancer or severe secondary infection — a progressive welfare decline that is preventable through vaccination. FeLV-positive cats require careful monitoring and management to maximise quality of life during the period before disease progression. Secondary infections must be treated promptly; regular blood work monitors for anaemia and lymphoma. Euthanasia decisions for FeLV-positive cats should be guided by quality of life assessment rather than diagnosis alone — many positive cats maintain good welfare for extended periods.

What You Can Do

Vaccinate cats with outdoor access or multi-cat exposure against FeLV as part of their core vaccination schedule.
Test newly acquired cats or those with unknown history for FeLV before introducing them to resident cats.
Provide FeLV-positive cats with indoor-only housing to prevent disease spread and reduce infection risks.
Monitor FeLV-positive cats regularly for quality of life changes and secondary disease requiring management.