THE EFFECT OF HIGH AND LOW-DOSE THEILERIA-PARVA INFECTION ON THE REPRODUCTIVE FUNCTION OF BORAN/FRIESIAN HEIFERS

Two separate experiments were carried out to find the effect af infection with low and high doses of Theileria parva sporozoites on the cyclical status of Boran/Friesian cross heifers. In each experiment, ten heifers were infected and another four heifers acted as controls. Routine monitoring of estrous behavior, determination of serum progesterone concentrations and palpation of the ovaries per rectum were used to assess the cyclical status of each animal. Two and eight animals died in the T. parva low (TpL) and high (TpH) dose experiments, respectively. Five of eight recovered animals in the TpL group cycled regularly postinfection, while three others had extended periods af ovarian dysfunction postinfection. Both infected and recovered animals in the TpH-group similarly had extended periods af ovarian dysfunction postinfection. All controls io both experiments cycled regularly throughout the study period. Differences in cyclical status were nat related to the febrile response, parasitological or hematological differences. The animals that continued to cycle throughout last the least amount of weight. Animals that stopped cycling lost between 16 and 29% of their initial body Heights postinfection. In conclusion, this study confirmed previous anecdotal evidence that theileriosis has an adverse effect on reproduction. Results of this study suggested that this was as an indirect result of weight lass associated with infection and not directly attributed to pathology of target organs.