Theileria annulata: control measures, diagnosis and the potential use of subunit vaccines.

Theileria annulata is an important pathogen of domestic Bovidae across a broad region of the world with some 250 million cattle at risk. Our basic knowledge of the incidence and mortality is reviewed together with an outline of current control measures, including the use of acaricides, chemotherapy and attenuated cell line vaccines. The limitations and potential problems of these control measures are discussed and considered in relation to the use of a subunit vaccine. Research over the last ten years on the protective immune response to the disease in both laboratory and field studies suggests that a humoral immune response to the sporozoite could be protective although the primary protective response appears to be mediated by cytotoxic T-cells recognising the macroschizont-infected lymphocyte stage. Recent work on the study of protective antigens using recombinant DNA and hybridoma technologies is discussed together with the potential advantages and problems of such approaches. Possible future developments in our understanding of the immune response and the identification of the relevant antigens are considered in addition to the use of new techniques for diagnosis and the analysis of parasite diversity.