A study of some factors influencing the epidemiology of urinary schistosomiasis at Ifakara (Kilombero District, Morogoro Region, Tanzania).

Some factors influencing the epidemiology of urinary schistosomiasis were studied at Ifakara between 1978 and 1980. Ifakara is situated in the fertile plain of the Kilombero river in the south-eastern part of Tanzania. The overall prevalence of Schistosoma haematobium infection among primary school children (6-19 years) in the Ifakara agglomeration was 21% (730/3478). The highest prevalence was observed in both sexes in the age group 15-19 years. Distinct variations in prevalence were found between the individual schools examined, ranging from 5 to 71% and indicating a focal transmission of the disease. The intensity of S. haematobium infection in the individual schools was relatively low, ranging from 5 to 36 eggs/10 ml urine. However, the frequency of microhaematuria among infected subjects was high, reaching 100% from an egg output of 50 eggs/10 ml onwards. Forty-nine waterbodies--most of them man-made--with Bulinus (Ph.) globosus and/or B. (Ph.) nasutus were found, 12 of them harboured B. (Ph.) globosus shedding cercariae of the mammalian type. These waterbodies were mainly localized in the northern and north-eastern areas of Ifakara where the primary schools with the highest prevalence of S. haematobium were found. Most of these waterbodies were known to be bathing places for the children. Susceptibility experiments with B. (Ph.) globosus and B. (Ph.) nasutus indicated that B. (Ph.) globosus is possibly the only intermediate host for S. haematobium in the areas examined. No Biomphalaria, the intermediate hosts for S. mansoni, were found. In addition, the knowledge and awareness of the local population about urinary schistosomiasis were assessed by a questionnaire survey.