Plasmodium schwetzi, a tertian malaria parasite that naturally infects chimpanzees and gorillas, was transmitted through the bites of Anopheles balabacensis balabacensis mosquitoes from the chimpanzee to man. Two of three volunteers exposed to infection by the bites of infected mosquitoes became infected, with prepatent periods of 24 and 104 days. The infection was passed successfully to nine of 10 additional volunteers by the intravenous inoculation of parasitized human blood. The two volunteers in whom patent parasitemia did not develop were Negroes. Patent infections persisted for up to 145 days with a maximum count of 2,750 parasites per cmm of blood. Maximum temperature observed in any of the volunteers was 105.6°F. The characteristics of the infections were compared with those observed in other simian malaria infections in man. The fact that P. schwetzi can be successfully transmitted to man by mosquito bite establishes its potentiality as a zoonosis for Africa.
Department of Pharmacology, Louisiana State University Medical School, 1190 Florida Avenue, New Orleans, Louisiana 70119.
Tulane University, Delta Regional Primate Research Center, Covington, Louisiana 70433.