Dynamics of insecticide resistance and exploring biochemical mechanisms involved in pyrethroids and dichlorodiphenyltrichloroethane (DDT) cross-resistance in Anopheles gambiae s.l populations from Benin, West Africa

As a result of the free-insecticide treated net distribution by National Malaria Control Programme (NMCP) in July 2011 throughout the entire country, it is useful to investigate the dynamics of insecticide resistance in Anopheles gambiae from Benin and the metabolic resistance mechanisms involved in this evolution of resistance. Larvae and pupae of A. gambiae s.l. mosquitoes were collected from the breeding sites in Littoral, Oueme and Zou departments. Centers for Disease Control and Prevention (CDC), bioassays were performed with permethrin (21.5 µg per bottle) and dichlorodiphenyltrichloroethane (DDT) (100 µg per bottle) whereas World Health Organization (WHO) susceptibility tests were performed with lambdacyhalothrin (0.05%). CDC biochemical assays using synergists piperonyl butoxide (PBO) and ethacrynic acid (ETAA) were also carried out. A. gambiae Akron, Suru-lere and Bame populations were resistant to permethrin and DDT in 2008 and 2013. A. gambiae Akron and Suru-lere were resistant to lambdacyhalothrin in 2013. A. gambiae Akron were susceptible to this product in 2008 whereas lambdacyhalothrin resistance status in A. gambiae Suru-lere populations in 2008 required further investigation. Mono-oxygenases were involved in resistance of A. gambiae Suru-lere to pyrethroids whereas glutathione S-transferases (GSTs) may play a role in A. gambiae Akron and Suru-lere resistant to DDT. This study shows that metabolic resistance conferred by detoxifying enzymes is an indication of phenotypic resistance to both DDT and pyrethroids in Southern Benin. Key words: Dynamics, piperonyl butoxide, ethacrynic acid, insecticide, vectors, resistance.