Feline leukaemia virus (FeLV) is a major cause of illness and death in cats, causing immune suppression, anaemia, and cancer with significant welfare implications.
FeLV-positive cats experience chronic immune suppression leading to repeated infections, anaemia, and eventual lymphoma or other malignancies. The disease trajectory involves prolonged periods of illness with associated suffering from secondary infections and blood disorders. Vaccination of at-risk cats is the most important intervention. FeLV-positive cats can have good quality of life for extended periods with appropriate veterinary management and protection from stress and secondary infections. Responsible cat ownership including testing, vaccination, and indoor management can largely prevent FeLV.