Fifty-four primates were exposed to single graded doses of 50 to 2000 cercariae of Schistosoma mansoni (Puerto Rican strain). They belonged to the following ten species: Macaca mulatta (rhesus monkey), Macaca cynomolgus (irus monkey), Macaca speciosa (stump tail monkey), Cebus apella (capuchin monkey), Ateles geoffroyi (spider monkey), Papio anubis (baboon), Pan satyrus (chimpanzee), Callithrix aurita (marmoset), Saimiri sciureus (squirrel monkey), and Tupaia sp. (tree shrew).
While all of these species could be experimentally infected with S. mansoni, their susceptibility and course of infection varied considerably. Variations in the intensity and type of tissue responses were also observed at various dosage levels. In general, three major reaction patterns could be distinguished: In the rhesus, irus and stump tail monkeys, there was a high percentage recovery of worms, good worm development and numerous infective eggs widely distributed throughout the colon, small intestine and liver. After a few months following infection, in these animals there was a tendency toward gradual self-cure. In the baboon and chimpanzee there was a lower worm recovery but egg excretion was maintained over relatively long periods. Most of the eggs were in the colon. In the marmoset, squirrel monkey and tree shrew, the infection tended to be aborted from its onset. The worm and egg recoveries were low, the miracidial infectivity for snails was also low or absent and the pathological features were irregular and atypical. There is not yet sufficient available evidence to determine the exact position of the capuchin and spider monkeys.
None of the primates included in these studies developed pipe-stem fibrosis of the liver in any way similar to that of man except for the chimpanzee which showed moderate portal fibrosis and development of portocaval collateral anastomoses. The liver architecture was generally preserved even among the monkeys of the third group which had large and fibrotic pseudotubercles.
No obvious correlation could be observed between susceptibility, phylogenetic position and the habitat of the primates studied.
Department of Medical Zoology, Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington, D. C.
Department of Pathology, Peter Bent Brigham Hospital and Harvard Medical School, Boston, Massachusetts.