The epidemiology of schistosomiasis in the later stages of a control programme based on chemotherapy: the Basrah study. 3. Antibody distributions and the use of age catalytic models and log-probit analysis in seroepidemiology

A comparative seroepidemiological survey of Schistosoma haematobium infection among primary schoolchildren in areas of different levels and patterns of endemicity in Basrah governorate, southern Iraq, also covered all inhabitants of Al-maadan locality, a known endemic focus in Basrah. Blood samples were tested by the enzyme linked immunosorbent assay. Serological data were analysed to describe the pattern of distribution of antischistosomal antibodies, to relate the level of infection to age and sex, and to estimate the force of infection per year by applying age catalytic models. The distributions of antibodies among the study populations were positively skewed; 3 patterns were revealed by relating serological data to age and sex, depending on the level of infection. The simple catalytic model was the best to estimate the force of infection among the younger age groups.