Feline leukaemia virus (FeLV) is a retrovirus of domestic cats worldwide. Cats lacking strong FeLV-specific immunity and undergoing progressive infection commonly develop fatal FeLV-associated disease. Many aspects of FeLV infection pathogenesis have been elucidated, some during more recent years using molecular techniques. It is recommended that the FeLV status of every cat is known, since FeLV infection can influence the prognosis and clinical management of every sick cat. Knowledge of a cat’s FeLV status is of epidemiological importance to prevent further spread of the infection. The question is… how often are you testing for this important disease? Diagnosing FeLV infection remains challenging due to the different outcomes of infection, which can vary over time depending on the balance between the virus and the host’s immune system. Furthermore, testing for FeLV infection has become more refined over the years and now includes diagnostic assays for different viral and immunological parameters. The question is… which test is best and when? This webinar presents recent knowledge on FeLV pathogenesis, key features to be determined in FeLV infection, and frequently used FeLV detection methods, and their characteristics and interpretation. This webinar is provided by BSAVA Education Partner IDEXX. A collection of IDEXX ‘topic of the month‘ webinars is available here.