Feline Leukaemia Virus (FeLV) is a significant welfare concern in cats, causing immunosuppression and cancer, but vaccination and testing programmes can prevent infection and manage affected cats.
FeLV causes progressive immunosuppression, anaemia and lymphoma, causing significant suffering over the course of infection. Prevention through vaccination of at-risk cats and testing of new additions to multi-cat households prevents most infections. FeLV-positive cats should not be euthanised on diagnosis alone - with appropriate care and monitoring, many live comfortably for years.