Immunity in theileriosis.

The theilerioses can be separated on the basis of their principal pathogenic features, into a lymphoproliferative group caused by Theileria parva and T. annulata in cattle, and T. hirci in goats and sheep, and a haemoproliferative group caused by T. sergenti and T. mutans both in cattle. In the former group, proliferation of parasites within lymphoid cells followed by lymphodestruction are the main pathogenic features; whereas in the latter group, invasion and destruction of erythrocytes, causing anaemia, are more important. In addition, a number of other theilerial parasites which cause mild or inapparent infections, are found in domestic livestock. This review focuses on T. parva, the causative agent of East Coast fever (ECF) in cattle in East and Central Africa, because it is the most pathogenic species and the immunology of ECF has been more intensively studied than that of the other theilerioses.