124 small mammals around the Americana Reservoir (=Salto Grande Reservoir) were trapped during the period January, 1972 to August, 1975, in places where human and snail (Biomphalaria tenagophila) infections by S. mansoni have been recorded. The mammals included: 44 specimens of Cavia aperea aperea, 9 Didelphis albiventris, 7 Holochilus brasiliensis leucogaster, 39 Lutreolina crassicaudata, 3 Mus musculus brevirostris, 14 Oryzomys nigripes eliurus, 1 Oryzomys subflavus, 4 Rattus rattus and 3 Zygodontomys brachyurus. Two D. albiventris, 3 H. b. leucogaster and 5 L. crassicaudata were found naturally infected with S. mansoni. The presence of eggs was verified in feces and intestines and the worm burden was determined through recovery of schistosomes from mesenteric vessels and the hepatic portal system. The mature eggs of S. mansoni were rarely found in the feces of L. crassicaudata and D. albiventris although they were common in H. b. leucogaster. The low abundance of H. b. leucogaster in the study area probably indicates that this rodent contributes little to the dissemination of S. mansoni eggs. It does not appear that the small mammals in this region have an important role in maintaining the S. mansoni life cycle.
Schistosoma mansoni; Mammals; Rodents; Carrier state