The role of human water contact patterns in the transmission of schistosomiasis in an informal settlement near a major industrial area.

Human contact with schistosome-infested water was studied in a rapidly growing community near an industrial area: water-contact was observed and categorized; interviews concerning water usage were conducted and schoolchildren and adult women were tested for schistosome infections. Results indicated that swimming amongst certain young people was an important contact activity in summer. To a lesser extent the washing of clothes and blankets was found to be an activity of importance, providing a focus for the social gathering of women and young children in contact with the water throughout the year. One of the aims of the study was to develop cost-effective methods for use in this and other endemic areas to provide guidelines for control programmes. A comparison was made between methods of assessing exposure to the infection in their ability to predict the prevalence of Schistosoma haematobium and S. mansoni across age-sex classes of the human host; an exposure index which included an assessment of body surface area was found to be preferable to one based on duration of contact only. The differing relationships between exposure to infested water and prevalence of the two schistosome species were in accordance with reports from other areas, thus supporting the choice of minimum requirements for a survey prior to control.