A six-year follow-up of schoolchildren for urinary and intestinal schistosomiasis and soil-transmitted helminthiasis in Northern Tanzania

Two cross-sectional studies with a 6-year interval were undertaken in two primary schools in neighbouring villages in Mwanga District, Tanzania, to determine the prevalence of schistosome and soil-transmitted helminth infections before and 6 years after treatment. Within this interval, health-related interventions such as one mass treatment of the villagers, health education, improvement of sanitation and access to safe water were undertaken in the villages. In 1996, urinary schistosomiasis occurred in Kileo (n=284) and Kivulini (n=350) in 37.0 and 86.3% of the schoolchildren. Intestinal schistosomiasis was found in 22.9 and 43.5% of the children. The infection with soil-transmitted helminths ranged between 2.7 and 18.1% in both villages. After 6 years, the prevalence of urinary schistosomiasis in schoolchildren remained nearly constant in Kileo (33.5%; n=544), but dropped from 86.3% to 70.0% in Kivulini (n=514). In the latter village the proportion of children heavily infected with Schistosoma haematobium (> or = 50 eggs/10 ml urine) decreased from 53.8% to 34.4%. With the exception of hookworm infection, soil-transmitted helminthiasis and intestinal schistosomiasis were significantly less seen in 2002 compared to the baseline. The previous chemotherapy of schoolchildren and villagers in 1996 and 1998, respectively, might have led to a reduced transmission of schistosomiasis in the following years. However, the reduction of prevalence of soil-transmitted helminthiasis is more likely to be the result of health-related interventions.