Figure 1

Top panel: the study sites; Bottom panel: study design. Illustration of a typical pair of intervention (right) and control (left) clusters with randomized pair-wise experimental design. Bti application (green dash-lined) covered the entire intervention cluster. Each cluster was divided into targeted (coloured area) and non-targeted (no background colour) areas and IRS was only applied in the targeted area within the intervention clusters. Buffer zones (250 m in width) are the areas where samples were not included in final analysis.