Outdoor residual spraying for malaria vector-control in Kayin (Karen) state, Myanmar: a cluster randomized controlled trial by Chaumeau, V, Kajeechiwa, L, Kulabkeeree, T, Sawasdichai, S, Haohankhunnatham, W, Inta, A, Phanaphadungtham, M, Girond, F, Herbreteau, V, Delmas, G, Nosten, F