PATTERNS OF TRYPANOSOMA-VIVAX AND T. CONGOLENSE INFECTION DIFFER IN YOUNG NDAMA CATTLE AND THEIR DAMS

Trypanosome infection was detected by the dark ground/phase contrast b uffy coat microscopic technique in N'Dama cattle in a high natural tse tse challenge situation in Zaire. The data were used to compare the pa ttern of infection in very young animals and in their dams, and to eva luate how the pattern evolved in calves from birth to maturity, and th ereafter in the different age groups represented by their darns. Five hundred and fourteen calves were evaluated at 3 week intervals for an average of 26 months each, over varying periods between birth and 42 m onths of age, Two hundred and sixty nine dams had matching records fro m parturition to calf weaning at 10 months. One month after weaning, a nimals were equally infected with Trypanosoma vivax and Trypanosoma co ngolense. From then until 42 months, the proportion of time an animal was infected with T. vivax relative to T. congolense gradually decreas ed. In the dams this trend continued from 4 years to at least 8 years of age by which time T. vivax infection was only one-third that of T. congolense infection. This finding is regarded as strong evidence of t he ability of N'Dama cattle, in this region of Africa, to acquire sign ificant control of the development of parasitaemia following T. vivax infection but apparently not following T. congolense infection. Pre-we aner calves, grazing with their darns, appeared to have considerable p rotection from, or be more resistant to, both T. vivax and T. congolen se infections compared with their dams and to their own immediate post -weaning situations. More sensitive diagnostic techniques such as anti body and antigen-detection enzyme immune-assays may help differentiate between pre-weaners that may not be infected and those that may be ca pable of controlling the development of detectable parasitaemia.