Knock down efficacy of commercially available insecticides against Anopheles gambiae

Abstract

Knockdown efficacy of commercial aerosol insecticides against laboratory reared Anopheles gambiae Kisumu strain mosquitoes and suppression of indoor resting density of A. gambiae complex mosquitoes in the field were investigated in the study. Laboratory reared 2-5 days old female A. gambiae mosquitoes were released into Peet-Grady chambers, sprayed with 0.3±0.1g of insecticides. Knock down rates were observed for one hour and mortality rates after 24hrs of spraying. Field efficacy studies were carried out by spraying houses with near uniform indoor resting densities of A. gambiae complex mosquitoes with aerosol insecticides and mosquitoes collected. Morphological and molecular characterization of mosquitoes was done. Probit analysis on knock down rates was carried out. Mortality rates and Mean indoor resting densities were compared using ANOVA in SPSS version 16. The KT50 and KT95 of Kenyan Baygon® and Kenyan raid® differed significantly with the other insecticides. Nigerian Baygon® achieved the lowest mortality rate of 87% and differed significantly (P<0.05) with other insecticides. No significant differences in suppression of indoor resting densities of A. gambiae complex mosquitoes was observed (p>0.05). Collected A. gambiae complex mosquitoes corresponded to A. arabiensis. The low knock down values by Kenyan Baygon® , Kenyan raid® and the low mortality rate by Nigerian Baygon® can be attributed to reduced efficacy rather than development of resistance. Whether the low deterrence of Anopheles gambiae complex mosquitoes into houses is due to development of pyrethroid insecticide resistance can be authenticated in another study