The epidemiology, immunology and morbidity of Schistosoma haematobium infections in diverse communities in Zimbabwe. I. The study design.

Recent studies on the immunology and epidemiology of Schistosoma haematobium infection have led to several new hypotheses regarding the relationships between the transmission of infection and the development of resistance to infection and also the associations between particular antibody and cellular reactivities with resistance or susceptibility to reinfection after chemotherapy. The study will extend the information on the development of protective immune responses during Schistosoma haematobium infection by examining these responses in groups of children and adults from areas in which differences in the peak prevalence of infection have been reported. Our working hypothesis is that, in areas of intense transmission, resistance to infection develops sooner than in areas where transmission is not so intense. We will investigate whether or not this is the case by monitoring levels of reinfection after chemotherapy and by trying to relate observed resistance and susceptibility to reinfection to serological and cellular reactivities. Exposure to infection, cercariometry and malacological studies will also be completed in both areas. The possibility that resistance to infection is associated with T lymphocyte responses classed as Th-2 type will be investigated by assessing reactivities to defined antigens of S. haematobium. This study will generate data which will be used to develop and test mathematical models of the epidemiological determinants which are important in human schistosomiasis.