Maedi-visna in sheep is a chronic viral disease with worldwide distribution causing significant monetary losses in the sheep sector. Lack of effective treatment or vaccines, knowledge gaps regarding the epizootiology of the disease (e.g. significance of vertical and horizontal transmission) and the scarcity of protocols for the early and efficient diagnosis of maedi-visna infections are the major obstacles in the implementation of universally accepted control programs. The diagnostic methods currently used are based on the detection of either antibodies or the viral genome. In general, accuracy, sensitivity and specificity of the available serological and molecular assays vary and therefore, modifications on the diagnostic protocols on an evidential basis are necessary. Therefore, the combination of diagnostic assays and the development of effective strategies for mass implementation thereof are critical targets to achieve and constitute major challenges in maedi-visna research field.