Schistosoma japonicum infection in monkeys and baboons: parasitological and pathological findings.

Abstract

The parasitologic and pathologic features of Schistosoma japonicum infection were studied in capuchin, grivet, and rhesus monkeys, and in baboons. Animals were killed 3 and 7 months after exposure to 50, 100, or 200 cercariae per kg body weight. Heavy infections developed in all monkey species, and moderately heavy infections in baboons. Rhesus and grivet monkeys became immune, and in these hosts many worms died between the 3rd and 7th months of infection. The fecundity of surviving worms was also markedly decreased in immune rhesus monkeys. The magnitude and rapidity of development of host immunity were much greater in the more heavily infected animals. Moderate hepatic portal fibrosis developed by the 3rd month after infection in capuchin monkeys, but 4 months later these lesions had not progressed to unequivocal pipe-stem fibrosis in spite of continued active infection. Portal pressure remained normal and portal-systemic collateral veins were not seen. Only focal portal fibrosis was seen in the other host species. Marked segmental lesions of the intestine were observed in all infected primates. These regressed rapidly in immune animals, and host destruction of S. japonicum eggs appeared to be rapid in all infected animals.