Schistosomiasis is a flatworm transmitted from freshwater snails to humans in the tropics. In addition to this infectious disease, tropical developing countries are faced with malnutrition. We propose to alter pesticide and compost use to reduce schistosomiasis and maintain or even improve crop production.

We propose two types of manipulations. Bottom-up manipulations will affect snail resources, whereas top-down manipulations will affect snail predators. For the bottom-up manipulations, we will clear schistosoma infections in school children, then remove the primary habitat for snails, the submerged macrophyte Ceratophyllum demersum (with proper unmanipulated controls), compost it, apply it to crops, and then quantify reinfection rates and crop yields. The second bottom-up manipulation will be to clear schistosoma infections in school children, apply three agrochemical treatments (status quo control, shift to lower risk herbicides, or eliminate herbicides and fertilizers), and then quantify reinfection rates and crop yields. Farmers will be compensated for any loss in yields. For the top-down manipulations, every village will receive prawns that depredate snails. We will clear schistosoma infections in school children, apply three agrochemical treatments (status quo control, shift to lower risk insecticides that don't kill prawns, or eliminate insecticides), and then quantify reinfection rates and crop yields. Farmers will be compensated for any loss in yields.

Inclusion Criteria:

• School age children

Exclusion Criteria:

• Non-school age children