Dynamics of Schistosoma haematobium infection in a Gambian community. I. The pattern of human infection in the study area.

The roles of some of the factors thought to be responsible for the characteristic relationship between age and the intensity and prevalence of Schistosoma haematobium infection have been investigated. In this initial report a study population in an area of intense infection is described, as are the methods used. Subsequent papers report the effect of interrupting transmission with molluscicide in part of the area and compare changes in egg count in this treated area with changes in an area where no intervention took place. These allow a consideration of age-specific rates of loss and acquisition of infection to be made. The intensity and prevalence of infection varied between villages both in the treated and untreated areas, but the relation of age to the pattern of infection was regardless of the level of infection in the villages. Over-all, the number of subjects and their pattern of infection was similar in both areas. The prevalence of infection tended to be higher in adult males than females but preliminary water contact observations suggest males are less exposed to infection. Observations over the three-year study period emphasize the extent of population movement in the study area and point to its importance in the planning of control measures.