The study was conducted in the context of a national schistosomiasis and soil-transmitted helminths (STH) control programme in Tanzania, which was established in 2003 with support from the Schistosomiasis Control Initiative (SCI) and funded by the Bill and Melinda Gates Foundation. Following WHO guidelines, the programme classifies communities on the basis of prevalence of schistosomiasis in school-age children, according to three strategies: 1) schools where prevalence is <10%, praziquantel is to be made available in local health centres, 2) schools where prevalence is 10 - 50%, mass treatment of all school age-children in the community is conducted and 3) schools where prevalence is >50%, mass treatment of all school age children plus other high-risk groups in the community is conducted. Because of the widespread distribution of STH in Tanzania, albendazole is co-administered with praziquantel.
In the first year of implementation (2005), five regions1 in coastal Tanzania and six regions in northwest Tanzania will be targeted for mass drug administration. Our study was conducted as part of the intervention in northwest Tanzania. For logistical reasons, data collection was limited to a 670 × 530 km area incorporating Kagera, Mwanza, Shinyanga and Tabora regions (see inset, Figure 1), with the aim of making spatial predictions in all six regions (including Mara and Kigoma).