Schistosomiasis mansoni in Bananal (State of São Paulo, Brazil): II. Intermediate hosts.
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 16.5 degrees C to 21 degrees C; 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.
Teles
Horacio Manuel Santana
HM
Laboratório de Malacologia, Coordenação dos Laboratórios de Referência e Desenvolvimento Científico, Superintendência de Controle de Endemias, São Paulo, SP, 01027-000, Brasil. horacio@sucen.sp.gov.br
Ferreira
Cláudio Santos
CS
de Carvalho
Maria Esther
ME
de Lima
Valquíria Rosa
VR
Zacharias
Fabiana
F
D000818:Animals; D001700:Biomphalaria; D001938:Brazil; D004199:Disease Vectors; D005247:Feeding Behavior; D005618:Fresh Water; D006801:Humans; D011156:Population Density; D012499:Sanitation; D012550:Schistosoma mansoni / Q000302:isolation & purification / Q000502:physiology*; D012555:Schistosomiasis mansoni / Q000635:transmission*; D012621:Seasons; D012908:Snails / Q000469:parasitology*; D013045:Species Specificity; D014505:Urban Population