FeLV is a serious retrovirus affecting cats that causes immunosuppression, cancer, and death, but is highly preventable through vaccination and testing protocols.
FeLV-positive cats experience progressive immune failure that leads to repeated infections, cancer development, and a cascade of health problems that cause suffering over months to years. The virus can cause anemia, lymphoma, and secondary infections that require ongoing management. Vaccination has dramatically reduced FeLV prevalence in well-managed cat populations, making the ongoing suffering from FeLV in unvaccinated and untested cats largely preventable. Early detection allows isolation to prevent spread and preparation for supportive care.