RESEARCH NOTE - Identification of a Transmission Focus of Schistosoma mansoni in the Southernmost Brazilian State, Rio Grande do Sul

The southern known limit of occurrence of Schistosoma mansoni Sambon 1907 in Brazil was the northeast of the State of Santa Catarina. In Rio Grande do Sul (RS) , Brazil's southernmost state, Biomphalaria tenagophila, B. straminea and B. peregrina were known to occur, but both mollusc and human infection was never documented as autochthonous. The infected child found in São Valentim, RS, came with his family from the endemic area in Minas Gerais and was not considered as an autochthonous infection by the Sucam. B. glabrata was reported for the first time in RS after the finding of S. mansoni eggs in a patient (OJSP) living in Esteio (20 km from Porto Alegre), that was initially considered as an imported infection. An extended epidemiological investigation gave support to the idea of an autochthonous infection, even though the source of infection could not be identified

The initial epidemiological studies in the low endemicity schistosomiasis area in esteio, Rio Grande do Sul, the southernmost Brazilian State, 1997 to 2000

Nor Biomphalaria glabrata neither Schistosoma mansoni were reported from Rio Grande do Sul, the southernmost Brazilian state before 1997. Their detection next to the Sinos River, Esteio, confirmed predictions of schistosomiasis expansion to the south. Parasitological examinations both in snails and fecal samples from the human population were performed from 1997 to 2000. The last 3 out of 5 surveys were performed after a preliminar serological screening procedure in a risk group identified at a population census. A total of 11 infected individuals were found infected and snails from 2 different sites were positive for S. mansoni. Samples from these 2 and other sites were identified as B. glabrata. Egg counts in feces were below 1 per gram in 6 out of 11 patients. Some socio-cultural perceptions of water contact activities next to the Sinos River may cause difficulties to control efforts, but they also may be partially acting against a very rapid increase in transmission intensity. The southernmost schistomiasis mansoni foci in Americas rise the alert for its ongoing expansion