Knock Down Efficacy Of Commercially Available Insecticides Against Anopheles Gambiae

Abstract

The study focused on the efficacy of commercially available aerosol insecticides from Kenya, Nigeria and South Africa against laboratory reared Anopheles gambiae Kisumu strain mosquitoes and Anopheles gambiae complex mosquitoes in the field. Laboratory reared 2-5 days old female Anopheles gambiae mosquitoes were released into peet-grady chambers, sprayed with 0.3±0.1g of insecticides. Knock down rates were noted for one hour and mortality rates noted after 24hrs of spraying. Field efficacy study was carried out by spraying houses insecticides with uniform indoor resting densities of Anopheles gambiae complex mosquitoes. The mean indoor resting densities of Anopheles gambiae complex mosquitoes in houses after spray were noted. Anopheles gambiae complex mosquitoes were morphologically identified and further subjected to molecular characterization using species diagnostic primers. The knock down rates were subjected to probit analysis and KTso, KT9s (Time taken to knock down 50% and 95% of mosquitoes respectively) obtained .The mortality rates were compared using LSD (ANOVA post hoc test) in SPSS version 16. The mean indoor resting densities of Anopheles gambiae complex mosquitoes of houses after spray with the insecticides were compared using ANOV A. Kenyan baygon'" and Kenyan raid® differed significantly with the rest of the insecticides with respect to KTso and KT9s. Nigerian baygon'" achieved the lowest mortality rate of 87% and differed significantly (P<0.05) with those achieved by the other insecticides. There were no significant differences in suppression of indoor resting densities of Anopheles gambiae complex mosquitoes in houses by the different insecticides (p>0.05). All the Anopheles gambiae complex mosquitoes collected from Kigoche village in Ahero corresponded to Anopheles arabiensis sibling species. The low mortality rates of An. gambiae mosquitoes and the poor performance of the insecticides

against Anopheles gambiae complex mosquitoes in the field could be attributed to reduced efficacy.