The genus Theileria comprises tick-transmitted sporozoan protozoa that are the causative agents of a variety of disease syndromes in domestic and wild ruminants, and are collectively responsible for economic losses amounting to hundreds of millions of dollars annually in Sub-Saharan Africa and Asia. There are six identified Theileria spp. that infects cattle. Theileria annulata causes tropical theileriosis, a disease which is present in northern Africa and southern Europe, extending through the Middle East, India, and southern Russia into China. The disease acts as a major constraint on livestock production and improvement in many developing countries. Mortality varies from 90% in introduced exotic breeds to 5% or less in indigenous breeds.