Comparative effects of permethrin-impregnated bednets and DDT house spraying on survival rates and oviposition interval of Anopheles farauti No. 1 (Diptera: Culicidae) in Solomon Islands

Abstract

Human-biting, CDC light trap and pig-baited collections were used to monitor changes in the abundance and parity rate of Anopheles farauti No. 1 mosquitoes in three Solomon Islands villages for 30 consecutive nights. Houses in one of the villages were sprayed with DDT, another village was unsprayed but its inhabitants used permethrin-treated bednets and the third village was left completely untreated. Mosquitoes collected each day were dissected to determine follicular maturation and parity. In the second year of vector control, survival rates (determined by time-series analysis of the landing catches and biting parous population) were significantly lower in the village using permethrin-treated bednets than in the other two villages. There was no difference in the estimated survival rates between the untreated and DDT-sprayed villages. The oviposition cycle was extended to 4 days in the permethrin-treated village compared with 3 days in the other villages. The expected infective life was 1·75-fold longer in the untreated village than in the permethrin-treated village. The epidemiological implications of replacing DDT spraying with permethrin for malaria control are discussed.