Occurrence of wild and human strains of Schistosoma mansoni in lower Amazonia: I - study in moluscs

Abstract

The wild (W) and human (H) strains of Schistosoma mansoni were isolated in the Lowland Region of the Maranhão State (Brazil). The snail progenies from Biomphalaria glabrata collected from that region were exposed to the W miracidia, obtained from livers of wild rodents, and H miracidia from eggs in human stools. A control gruop of normal snails was kept in the same conditions as the infected one. The date of the elimination of cercariae, the quantity of eliminated larvae, the infection index of the moluscs and the mortality rate of the snails were recorded. These data suggested better adaptation of the H strain to B. glabrata. The W strain presented three times more virulence to snails than the H strain. These results were compared with published data of H and W strain from the Paraíba do Sul River Valley and different parasitologic behavior was verified.