[Susceptibility of Biomphalaria tenagophila from the Paraná and Uruguay River basins to Schistosoma mansoni].

To study the possibility that schistosomiasis might be able to spread into the basins of the Paraná and Uruguay rivers, 1,711 snails were experimentally exposed to infection with Schistosoma mansoni. These snails were laboratory-bred progeny of Biomphalaria tenagophila collected from 15 populations in the geographic area under consideration. Three strains of S. mansoni were used: BH2, adapted to B. glabrata, and SJ and SJ2 adapted to B. tenagophila. None of the 543 snails exposed to the BH2 strain became infected, nor did any of the 668 exposed to SJ. However, of the 500 exposed the SJ2, 4 of the 163 snails (2%) from Ayolas, a locality in the Paraná basin, were susceptible, as were 8 of 45 (18%) from Fuente, Salto, in the Uruguay basin. These findings are similar to those of studies done in other geographic areas, where some populations of B. tenagophila do not become infected with S. mansoni while others are susceptible. The results of this study signal the possibility of the expansion of schistosomiasis into a broad region of South America in which B. tenagophila is found.