The objective of this study is to determine the strategy for mass drug administration (MDA) which provides the greatest reductions in prevalence and intensity of Schistosoma mansoni in school-aged children after 4 years of intervention.

Intestinal schistosomiasis is caused by the blood-dwelling flatworm Schistosoma mansoni. Despite the increasing focus on the use of praziquantel against schistosomiasis infections for the last three decades many areas in Sub-Saharan Africa still have high prevalences and intensities of schistosomiasis especially among school-age children. This is true for the area of Mwanza Region of Tanzania adjacent to Lake Victoria. The study is a six arm study and includes 150 communities (25 in each arm). From each community 100 school children (aged 9-12 years), 100 first year students (aged 7-8 years) and 50 adults (aged 20-55 years) are included, diagnosed and treated with praziquantel using strategies composing of a mixture of community wide treatment (CWT), school-based treatment (SBT) and years without treatment (-T). The 100 school children provided stool specimens on three consecutive days, while the 100 first year students and 50 adults with few exceptions only provided one specimen. The treatment strategies during the 4 years for the different arms are as follows: Arm 1: CWT, CWT, CWT, CWT; Arm 2: CWT, CWT, SBT, SBT; Arm 3: CWT, CWT -T, -T; Arm 4: SBT, SBT, SBT, SBT; Arm 5: SBT, SBT, -T, -T; Arm 6: SBT, -T, SBT, -T.

Inclusion Criteria:

-All school children and adults who consent to participate can be included

Exclusion Criteria:

-Those not consenting or with any chronic disease not related to schistosomiasis will be excluded