The abundance of pathogenic African trypanosomes in the salivary secretions of wild Glossina pallidipes.

Trypanosome infection rates in wild Glossina pallidipes from the Lambwe Valley, Kenya, were determined using salivation and fly dissection methods. Of the 416 flies examined by salivation, one was infected with Trypanosoma brucei, seven with T. congolense, 18 with T. vivax and three with both T. congolense and T. vivax. The fly infected with T. brucei always secreted saliva heavily infected with trypanosomes. Flies infected with T. vivax secreted saliva which contained very few trypanosomes and some of these flies produced negative saliva for several successive days. There was no significant difference between the proportions of male and female flies which were infected with any one species of trypanosome, but there were highly significant differences between the mean numbers of the different species of trypanosome in the saliva.