Geographic information systems and the environmental risk of schistosomiasis in Bahia, Brazil

A geographic information system was constructed using maps of regional envi ronmental features, Schistosoma mansoni prevalence in 30 representative mun icipalities, and snail distribution in Bahia, Brazil to study the spatial a nd temporal dynamics of infection and to identify environmental factors tha t influence the distribution of schistosomiasis. Results indicate that popu lation density and the duration of annual dry period are the most important determinants of prevalence of schistosomiasis in the areas selected for st udy. Maximum rainfall, total precipitation during three consecutive months, annual maximum or minimum temperatures, and diurnal temperature difference were not shown to be significant factors influencing S. mansoni prevalence in local populations or distribution of snail hosts. prevalence of the dis ease was highest in the coastal areas of the state. Higher prevalence tende d to occur in areas with latossolo soil type and transitional vegetation.