In rhesus monkeys and in a human volunteer typical cercarial dermatitis was observed, which subsided by the end of 1 week after exposure to the cercariae of Heterobilharzia americana.
H. americana evidently did not produce a patent infection in these primates; no eggs were passed in the stools of a rhesus monkey kept for observation over 5 months after exposure to the cercariae or in the stools of the human volunteer. Young schistosomules were recovered from the liver of a rhesus monkey at necropsy 21 days after exposure to the cercariae, whereas preadults were still alive in monkeys at necropsy 45 days after the onset of the infection.
In the liver there was a slight to moderate portal-tract and interlobular-space infiltration, and there were necrotic lesions with early fibroepithelial pseudotubercle organization. Inflammatory infiltration was also observed in the lung.
In these monkeys the infection was accompanied by a moderate eosinophilia, starting about the 4th day after exposure to the cercariae, and continuing for several weeks, after which the eosinophil count returned to about normal.
Detectable levels of antibodies were demonstrated in the sera of these monkeys at the end of the 1st week after exposure and lasted until 94 days, when the experiment was terminated.
Present address: Parasitic Diseases, Communicable Diseases Division, World Health Organization, Geneva, Switzerland.
Present address: NAMRU—3, Field Facility, Ethiopia. APO 09310, New York, N. Y.