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.

An epidemiologic study was conducted in San Cayetano, a village in the province of Corrientes, Argentina, to determine the prevalence of intestinal parasitoses in children. Eighty-eight households were randomly selected. Stool samples were collected from 207 children (72% of the school-age population and 12% of the total village population) over a period of six consecutive days, and were subjected to microscopic examination. Of the samples examined, 170 (83%) contained one or more parasites, of which the most frequently found was Blastocystis hominis (in 43% of the samples). Other parasites and commensals detected included Giardia lamblia (29%), hookworms (27%), Entamoeba coli (27%), Enterobius vermicularis (4%), Strongyloides stercoralis (2%), and Ascaris lumbricoides, Trichuris trichiura, Taenia saginata, Isospora belli, Iodamoeba bütschlii, and Balantidium coli (each 0.5%). The high observed prevalence of intestinal parasitoses indicates active parasite transmission in San Cayetano as a result of poor environmental hygiene-ascribable largely to a lack of public water supply, sewerage, and waste removal services.

A survey conducted near a dam-site on the Paraguay-Argentine border showed the area to be highly endemic for Chagas’ disease. It also showed that new housing unsuited to the disease vector’s prol$eration did not eliminate the prob/em, indicating a strong need for health education capable of guiding people away from traditional behavior patterm tending to encourage the vector and cause infection.