3.2 Intervention by mass drug administration Prior to the transmission season, all individuals will receive either mass drug administration (MDA) or placebo. This administration is done irrespective of the presence of parasites or symptoms. Treatment dosage is sulphadoxine- pyrimethamine (Fansidar, Roche, Switzerland: S 500mg/20kg; P 25mg/20kg, day1), artesunate (Arsumax, Sanofi, France: 4mg/kg, day1,2,3) and primaquine (PQ base, Radboud University Nijmegen, The Netherlands: 0.75 mg/kg) Pregnant women and children below 1 year of age will be excluded from PQ treatment.