THE INTERACTION OF TRYPANOSOMA-CONGOLENSE AND HAEMONCHUS-CONTORTUS INDJALLONKE SHEEP

The interaction between Trypanosoma congolense and Haemonchus contortu s was studied in 5 groups of 8 Djallonke sheep. Two groups received a single infection with either H. contortus or T. congolense, and 2 grou ps were infected with T. congolense followed by H. contortus (TH) or v ice versa (HT). One group was kept as uninfected controls. Mortality d ue to infection was observed only in the dual infection groups. In the TH group, the effects were more acute whereas in the HT group they we re more chronic. No significant differences in weight gain could be de monstrated between infected and control groups. Djallonke sheep are ab le to withstand a single infection with either T. congolense or H. con tortus, which confirms their trypanotolerant nature and provides preli minary indication of resistance against helminth infections. However, when exposed to successive infections with both parasites, some of the animals lose this tolerance. (C) 1997 Australian Society for Parasito logy. Published by Elsevier Science Ltd.