Study Design and Participants

A cluster-randomized controlled trial (CRCT) was used to evaluate the impact of the mass treatment interventions on study end points. The trial area was stratified into higher- and lower-transmission strata above and below 10% parasite prevalence at randomization. The study was conducted in Southern Province, Zambia along Lake Kariba in 60 health facility catchment areas (HFCAs) in 10 districts (Figure ​(Figure1).1). The entire study area was enumerated by a geographic information system in 2013 and 2014 using personal digital assistants. Approximately 330 000 individuals in 56 000 households, primarily of the Tonga ethnic group, live in this area. Malaria parasite prevalence in children ranges from <1% in areas inland from the lake to >25% in areas closer to the lake. The season for high malaria transmission lasts from January to May, coinciding with seasonal rains.

Map of the study area, divided into 60 health facility catchment areas that served as the unit of randomization. Abbreviations: fMDA, focal mass drug administration; MDA, mass drug administration; N, north.