Chemotherapy of East Coast fever: the long term weight changes, carrier state and disease manifestations of parvaquone treated cattle.

The weight changes, carrier state and nature of chronic disease in cattle following infection with five isolates of Theileria parva and treatment with parvaquone were studied over an 18 month period while the cattle were maintained on normal management under strict tick control. Cattle infected with the T.p. parva Pugu II isolate gained weight similarly to uninfected control cattle and did not develop a detectable carrier state or show chronic disease. The cattle in the 4 other isolate groups regained the weight lost during the initial infection more slowly, then gained weight in parallel to the control cattle. Transmission of infection through ticks was achieved consistently from the T.p. parva Mbita I and Entebbe II isolate infections and intermittently from the T.p. lawrencei Mara II and Manyara infections. Infections were transmitted from cattle which had neither a detectable parasitaemia nor an antitheilerial antibody titre. Persistent macroschizont parasitoses were detected with the T.p. parva Entebbe II and the two T.p. lawrencei infections. The histopathology of the chronic disease lesions is described and the importance of the carrier state discussed.