| Abstract: | A series of experiments is described in which infective material obtained by grinding adult Rhipicephalus appendiculatus ticks containing mature Theileria parva parasites was titrated in East Coast fever-susceptible cattle. The reactions of the cattle to the various inocula, and the rate of multiplication of macroschizonts in their lymph nodes, were studied. In the final experiment, conclusive evidence was produced to support the observations of previous workers that the prepatent period, time to onset of febrile response, and time to death of the animals was dose-dependent, whereas the production of intraerythrocytic piroplasms was totally time-dependent. Furthermore, the effective rate of multiplication of macroschizonts was shown for the first time to be dose-dependent. It was not possible to detect macroschizonts before the fifth day after inoculation, and an occult phase of the parasite's life cycle, between the infective particle and the uninuclear macroschizont, is postulated. The discrepancies between the results of the present work and those of previous workers are discussed. |
