An observation on the unexpected frequency of some multiple infections.

Studies of trypanosome infections in over 3 500 young and adult cattle in the Lambwe Valley of Kenya showed the presence of Trypanosoma congolense, T. vivax, and T. brucei in single or multiple infections. Some of the multiple infections were much more frequent than would have been expected on the basis of chance, but only if T. brucei was one of the infective agents. Some studies of malaria infections in man show a similar phenomenon.