In vitro phagocytic activity of neutrophils of various cattle breeds with and without Trypanosoma congolense infection.

A simple in vitro-technique using latex beads was used for the investigation of the phagocytic activity of neutrophils in bovines of different breeds, infected and non-infected with T. congolense. It was found that the N'Dama, assumed to be trypanotolerant, have a significantly higher number of neutrophils and neutrophils with phagocytic activity per mm3 blood, compared to the more susceptible Zebu, the Baoulé and the crossbreed M75, ranging between these two breeds. The first appearance of T. congolense in the blood was accompanied by a significant increase of phagocytizing neutrophils in 21 bulls of different breeds and 12 N'Dama cows in comparison to the pre-infection levels or to the animals which remained free of trypanosomes. A possible involvement of the neutrophils in the defence against trypanosomes by phagocytosis is discussed.