Multiple insecticide resistance target sites in adult field strains of An. gambiae (s.l.) from southeastern Senegal
Abstract Background: High coverage of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the cornerstones of vector control strategy in Senegal where insecticide resistance by the target vectors species is a great of concern. This study explore insecticide susceptibility profile and target-site mutations mechanisms within the Anopheles gambiae complex in southeastern Senegal. Methods: Anopheles larvae were collected from Kedougou and Wassadou/Badi, two sites from southeastern Senegal, in October and November 2014, and reared until adult emergence. Wild Fo Adults mosquitoes were morphologically identified to species. Susceptibility of 3-5-day old An. gambiae (s. l.) samples to eleven (11) insecticides belonging to the four insecticide classes was assessed using WHO insecticide susceptibility bioassays. Tested samples were identified using molecular techniques as well as detection of insecticide resistance target-site mutations (kdr, ace-1 and rdl).Results: A total of 3,742 An. gambiae (s.l.) were exposed to insecticides (2,439 from Kedougou and 1,303 from Wassadou-Badi). Tests with pyrethroid insecticides and DDT showed high level of resistance in both Kedougou and Wassadou/Badi. Pirimiphos-methyl and Malathion resistance were not detected while Bendoicarb and Fenitrothion resistance were confirmed in Kedougou. Of the 745 specimens of An. gambiae (s.l.) genotyped, An. gambiae (s.s.) (71.6%) was the predominant species, followed by An. arabiensis (21.7%), An. coluzzii (6.3%) and hybrids (An. gambiae (s.s.) /An. coluzzii; 0.4%). All target site mutations investigated (Vgsc-1014F; Vgsc-1014S, Ace-1 and Rdl) were found at different frequencies in the species of the Anopheles gambiae (s.l.). Vgsc-1014F mutation is more frequent in An. gambiae and An. coluzzii than An. arabiensis. Vgsc-1014S was present in An. gambiae (s.l.) populations in Wassadou but not in Kedougou. Ace-1 and rdl mutations were more frequent in An. gambiae (s.s.) in comparison to An. arabiensis and An. coluzzii. Conclusions: Resistance to all the four insecticide classes tested was detected in southeastern Senegal as well as all target site mutations investigated were found. Data will be used by the national Malaria Control Programme.