Factors conditioning the habitat and the density of Biomphalaria tenagophila (Orbigny, 1835) in an isolated schistosomiasis focus in Rio de Janeiro city

Abstract

The present work was carried out in a watercress garden in Alto da Boa Vista, in the city of Rio de Janeiro, Brazil. The investigation was carried out in two phases. The first one (1985-86) involved the sampling of Biomphalaria tenegophila in two areas to determine its relative populational densities. The results showed that the populations presented similar densities and dynamics. The second phase (1988-89) involved the study of the influence of some environmental factors on the establishment of B. tenagophila in watercress garden. Two factors were identified as responsible for the establishment of B. tenagophila in the garden: (1) the quality of the water entering the irrigation system, to which domestic sewage is added, and (2) alterations in the nature of the substrate, due to inadequate fertilization techniques, which employ organic matter from adjacent pigsties. Aquatic plants and hydrological parameters of the irrigation system were subsidiary factors to the establishment of B. tenagophila in the garden.

Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): II. Intermediate hosts

“…Concerning the shedding of cercariae, it was predominant in Pernambuco (Northeastern Brazil) during the dry season, as observed in Bananal, while the same occurred in Rio de Janeiro dur-L a ra n je ir a s R io B a n a n a l C e n tr o ing the rainy season. The slight variations in pH and temperature, observed during this study produced changes in snail population densities and the transmission of the infection, in agreement with the conclusions of Camargo (1977), Baptista et al (1989) and Baptista and Jurberg (1993). As regards water temperature, Ramos et al (1961) captured infected B. tenagophila specimens in the Valley of River Ribeira de Iguape during the winter, the water temperature being less than 19°C as a consequence of which the snail population density is lowest.…”

“…Pinotti et al (1960) in the State of Pernambuco (Brazil), Baptista et al (1989) and Baptista and Jurberg (1993) in the State of Rio de Janeiro, observed similar effects of the amount of rainfall. Concerning the shedding of cercariae, it was predominant in Pernambuco (Northeastern Brazil) during the dry season, as observed in Bananal, while the same occurred in Rio de Janeiro dur-L a ra n je ir a s R io B a n a n a l C e n tr o ing the rainy season.…”

Distribution and Schistosoma mansoni infection of Biomphalaria glabrata in different habitats in a rural area in the Jequitinhonha Valley, Minas Gerais, Brazil: environmental and epidemiological aspects

“…The pollution effect was due in part to vegetation density, with which it was significantly correlated (P = 0.003). Similar findings were also reported from an irrigated farm in Rio de Janeiro, where high levels of sewage and quality of water were associated with high B. tenagophila densities (Baptista & Jurberg 1993). Although less numerous in ferrugenous aquatic environments, B. glabrata occurs widely in areas of lateritic soil in Brazil, where it develops brown and black shells.…”

Habitat preference of freshwater snails in relation to environmental factors and the presence of the competitor snail Melanoides tuberculatus (Müller, 1774)

“…A study made by Buss et al (2004) in streams of that region demonstrated that the density of macroinvertebrates were negatively influenced by spates. The influence of rainfall on (Baptista & Jurberg 1993, Ernould & Sellin 1999, Teles et al 2002. Water flow in lotic environments is the most important factor for explaining the longitudinal distribution of the snails that are the intermediate hosts of Schistosoma spp.…”