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 infect ion with low and high doses of Theileria parva sporozoites on the cycl ical status of Boran/Friesian cross heifers. In each experiment, ten h eifers were infected and another four heifers acted as controls. Routi ne monitoring of estrous behavior, determination of serum progesterone concentrations and palpation of the ovaries per rectum were used to a ssess the cyclical status of each animal. Two and eight animals died i n the T. parva low (TpL) and high (TpH) dose experiments, respectively . Five of eight recovered animals in the TpL group cycled regularly po stinfection, while three others had extended periods af ovarian dysfun ction postinfection. Both infected and recovered animals in the TpH-gr oup similarly had extended periods af ovarian dysfunction postinfectio n. All controls io both experiments cycled regularly throughout the st udy period. Differences in cyclical status were nat related to the feb rile response, parasitological or hematological differences. The anima ls 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 previ ous anecdotal evidence that theileriosis has an adverse effect on repr oduction. Results of this study suggested that this was as an indirect result of weight lass associated with infection and not directly attr ibuted to pathology of target organs.