Heterophile antibodies to chicken erythrocytes in sheep infected with Trypanosoma congolense.

High hemagglutinin titres against chicken erythrocytes were detected in the sera of Trypanosoma congolense-infected sheep. Adsorption of sheep sera with solubilized T. congolense resulted in marked reduction of hemagglutinin titre. Heat inactivation of the sera at 56 degrees C for 30 min had no demonstrable effects on the hemagglutinin titre. Sera collected from the sheep before trypanosome infection did not agglutinate chicken erythrocytes. On the other hand, erythrocytes of horse, donkey and dog were agglutinated at very high titres by sera collected both pre-infection and during the course of infection. Erythrocytes from bovine and caprine species were not agglutinated by contemporaneous sera at both low and high dilutions. Hemagglutinin titres for chicken erythrocytes returned promptly to pre-infection levels in chemotherapeutically terminated infections. The brand of trypanocide used, had no effect on the course of the hemagglutinin titre's return to a normal level.