Geographical and socioeconomic factors relating to the distribution of Schistosoma mansoni infection in an urban area of north-east Brazil.

A study was carried out in Santo Antonio de Jesus, a town in Bahia State, north-east Brazil, to determine the relationship between various biological, socioeconomic, behavioural, and geographical factors and the prevalence and intensity of Schistosoma mansoni infection. The town's population was around 45,000 and the study was targeted at all children born in 1970-71 who were living in the town at the time of the survey (August-November 1984). An extensive questionnaire was used to collect information on each child and on family and household conditions; samples of stools were also taken for examination (Kato-Katz method). A survey of water snails was also carried out and information on the distribution of their breeding sites was plotted on a map of the area. The overall prevalence of S. mansoni infection was 31.0%. Several variables that reflected different aspects of the population's way of life were strongly associated with the prevalence and the intensity of infection. Some of the findings are valuable for understanding the mechanisms involved in the occurrence of schistosomiasis and its distribution in urban locations as well as for defining high-risk groups, all of which are important for planning control strategies.