Indoor residual spraying with alphacypermethrin controls malaria in Pakistan: a community-randomized trial

We conducted a community-randomized controlled trial in Pakistan to determi ne the efficacy of indoor residual spraying with alphacypermethrin ('Fendon a', Cyanamid, NJ, USA), applied at 25 mg/m(2), to prevent falciparum and vi vax malaria. Wettable powder (WP) and suspension concentrate (SC) formulati ons were tested against an unsprayed control in on irrigated rice-growing a rea of Sheikhupura district, Punjab province. The study area of 180 km(2) w as divided into nine sectors, which were assigned at random to control, WP, or SC treatments in replicates of 3. Sentinel villages were selected from each sector for entomological and disease monitoring. Malaria was monitored by fortnightly active case detection (ACD) and by cross-sectional parasite surveys on schoolchildren. Mosquito populations were monitored by space sp raying of rooms and by cattle-landing catches. The spray campaign took plac e in June 1997 and covered 96% of compounds. During the 7 months after spra ying, the incidence of falciparum malaria was 95% lower and that of vivax m alaria 80% lower in WP-sprayed than unsprayed sectors. Similar results were obtained fur sectors sprayed with the SC formulation. Cross-sectional surv eys gave estimates of efficacy comparable to those obtained by ACD. Anophel es culicifacies was 80% less abundant and A. stephensi, the predominant ano pheline, was up to 68 % less abundant in sprayed areas over the 7-month per iod. Reductions in anopheline parous rates indicated that the single-spray treatment was effective for the entire transmission season. Sprayed surface s lacked odour, which contributed to the popularity of the campaign. Alphac ypermethrin is a promising insecticide for the control of malaria in Pakist an and South Asia generally.