Current sensitivity status of Anopheles gambiae (s.l.) (Culicidae) to DDT and pyrethroids in two agricultural sites of Mouila, Gabon

Abstract

The present study was conducted during the rainy season of 2017 in Mboukou and Moutassou, two palm oil concessions located in the suburbs of Mouila city. It aimed at determining the susceptibility status of Anopheles gambiae s.l. to organochlorines and pyrethroids. The larvae and pupae of An. gambiae s.l. were collected from different breeding sites by the dipping method and reared to the adult stage in the field laboratory. The adult females were exposed to various insecticides: Organochlorine (DDT 4%) and Pyrethroids (Permethrin 0.75%, 3.75% and 7.75%; Deltamethrin 0.05%, 0.25% and 0.50%; Lambdacyhalothrin 0.05%, 0.25% and 0.50%). The sensitivity of An. gambiae s.l. populations to insecticides was assessed following WHO protocol. All tested mosquitoes were identified by PCR method. An. gambiae s.s. and An. coluzzii were the only anopheline species identified in all the prospected sites. The results of the susceptibility tests revealed that the malaria vectors of the surveyed sites were susceptible or resistant to the tested insecticides depending on the type and the dose of insecticide. These Anopheles were resistant to DDT 4% and low doses of pyrethroids (Permethrin 0.75%, Deltamethrin 0.05%, Lambdacyhalothrin 0.05%). But they were sensitive to all pyrethroids at high doses (98 to 100% mortality).