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vol.97 suppl.1Identification of snails within the Bulinus africanus group from East Africa by multiplex SNaPshotTManalysis of single nucleotide polymorphisms within the cytochrome oxidase subunit IFreshwater snails and Schistosomiasis mansoni in the state of Rio de Janeiro, Brazil: III - Baixadas Mesoregion author indexsubject indexarticles search
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Memórias do Instituto Oswaldo Cruz

Print version ISSN 0074-0276On-line version ISSN 1678-8060


TELES, Horacio Manuel Santana et al. Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): II. Intermediate hosts. Mem. Inst. Oswaldo Cruz [online]. 2002, vol.97, suppl.1, pp.37-41. ISSN 0074-0276.

We conducted monthly snail captures in Bananal, State of São Paulo, Brazil, between March 1998 and February 2001, to identify Schistosoma mansoni vectors, estimate seasonal population changes, and delimit foci. We also evaluated the impact of improvements in city water supply and basic sanitation facilities. We identified 28,651 vector specimens, 28,438 as Biomphalaria tenagophila, 49 of them (0.2%) infected with S. mansoni, and 213 as B. straminea, none of the latter infected. Vectors predominated in water bodies having some vegetation along their banks. Neither population density nor local vegetation could be linked to vector infection. We found the first infected snails in 1998 (from March to May). Further captures of infected snails ocurred, without exception, from July to December, when rainfall was least. Irrespective of season, overall temperature ranged from 16.5ºC to 21ºC; pH values, from 6.0 to 6.8. Neither factor was associated with snail population density. Frequent contact of people with the river result from wading across it, extracting sand from its bottom, fishing, washing animals, etc. Despite a marked reduction in contamination, cercaria shedding persists. Whatever the location along its urban course, contact with river Bananal, particularly of the unprotected skin, entails risks of infection.

Keywords : Biomphalaria tenagophila; seasonality; Schistosoma mansoni; transmission; São Paulo; Brazil.

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