Feline leukaemia virus (FeLV) is a retrovirus that causes immunosuppression, anaemia, and cancer in cats, and remains a significant welfare concern particularly in multi-cat environments and outdoor cats.
FeLV-positive cats experience chronic welfare impairment as the virus progressively damages the immune system, leading to recurrent infections, anaemia causing weakness and breathlessness, and eventual cancer development. The condition is ultimately fatal in persistently infected cats, typically within 2-3 years. Welfare management focuses on preventing secondary infections through vaccination of other diseases, prompt antibiotic treatment, nutritional support, and pain management for associated conditions. FeLV-positive cats should ideally be kept indoors to prevent transmission to other cats and to reduce their own exposure to environmental pathogens. Testing before introduction of new cats into multi-cat households is a critical prevention measure.