Theileria annulata

Theileria annulata is a tick-transmitted parasite that causes tropical theileriosis. It is distributed widely across southern Europe, north Africa, and Asia, where approximately 250 million cattle are at risk of T. annulata infection. The parasite's life cycle contains a sexual phase in tick vectors and asexual developmental stages in mammalian hosts. After invading host leukocytes, the parasites reprogram many host signaling pathways and induce replication via poorly understood molecular mechanisms. Within red blood cells, multiplication of T. annulata causes anemia that could aggravate the pathology of the disease. Buparvaquone is an effective drug for treating tropical theileriosis at the early infection stage; however, the relatively high cost limits its application worldwide. Currently, low-pathogenicity parasites derived from infected cells in vitro are used as vaccines in many countries.