Feline leukaemia virus (FeLV) is a serious retroviral disease of cats causing immunosuppression, anaemia, and cancer, with prevention through vaccination being the cornerstone of welfare.
FeLV welfare impacts are progressive: in the early stages, cats may appear well; as the virus causes immunosuppression, secondary infections become more frequent and severe; eventually lymphoma or severe anaemia significantly reduces quality of life. Regular monitoring of FeLV-positive cats allows welfare assessment and timely treatment of secondary problems. Supportive care including treatment of secondary infections, nutritional support, and monitoring for early lymphoma development extends welfare-positive life. The decision to continue or cease treatment requires ongoing quality-of-life assessment using validated tools. FeLV-positive cats should be kept indoors to prevent transmission and protect their own immune systems. Welfare advocacy includes promoting routine FeLV vaccination and testing before cat introductions to multi-cat households.