A study of schistosomiasis mansoni was performed in 9 marmosets. Six were exposed to a predetermined number of cercariae obtained from snails naturally infected with Schistosoma mansoni in Bahia, Brazil. Eggs were first observed in the feces 15 weeks after exposure; the ratio of worms to cercariae was low, averaging 5.2%, and the worms were stunted. In an additional experiment, worms isolated from marmosets 7.5 weeks after exposure to cercariae of S. mansoni were significantly smaller than worms isolated at the same time from a group of simultaneously exposed Swiss albino mice. None of the marmosets showed ill effects from the infection. It appears that the marmoset is resistant to infection with S. mansoni.
Visiting Professor of Medicine, University of Bahia, Bahia, Brazil. From the Laboratory of Parasitic Diseases, National Institutes of Health, Bethesda, Maryland. Present address: Department of Preventive Medicine, Western Reserve University, Cleveland, Ohio.
Associate Professor of Physiology, University of Bahia, Bahia, Brazil.