Control of lymphoproliferation by Theileria annulata.

The economic importance of bovine theilerioses has prompted several new approaches to understanding the diseases in the hope of developing more efficient methods of control. Most Theileria species that infect cattle cause a lymphoproli ferative disease. Sporozoites, injected into the host bloodstream by the tick vectors, rapidly invade host lymphocytes and stimulate rapid division of infected cells. As these rupture, merozoites are released which invade red blood cells ready to infect feeding ticks again. The process by which Theileria parasites can control host lymphocytes, and induce them to divide in synchrony with the parasites themselves, is poorly understood but seems to be the key to pathogenesis. In this article, Michael Dyer and Andrew Tait discuss the possible mechanisms of cellular control in the light of recent work revealing sequences homologous to oncogenes in the DNA of T. annulata.