Detection of multiple insecticide resistance mechanisms in Anopheles gambiae s.l. populations from the vegetable farming area of Houeyiho, Southern Benin, West Africa

摘要

A study carried out in a vegetable farming area (Houeyiho) in southern Benin, showed that despite thebenefits coming from this activity, its development contributes to the emergence of multiple insecticideresistance in malaria vectors.To verify this hypothesis, we reared wild mosquitoes’ larvae collected from a vegetable farming areaduring dry and rainy seasons. Bioassay were performed on the emerging adult mosquitoes to assess thesusceptibility of malaria vectors to insecticide-impregnated papers (permethrin 0.75%, delthamethrin0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. An. gambiae complex, knockdown resistance (kdr) and acetylcholinesterase (ace-1) mutations were determined by Polymerase ChainReactions (PCR).Enzymatic mechanisms (Glutathione-S-Transferase, esterase, monooxygenase P450 and total protein)were also investigated from the F1 (the parental population after breeding) populations of An. gambiaes.l.Results from this study showed that: a)-A wide range of pesticides is abusively used by farmers for cropprotection which would have contributed to insecticide resistance in An. gambiae populations toorganochlorines (average mortality rate = 1.19%) and pyrethroids (average mortality rate = 29%) butremains susceptible to carbamate (average mortality rate = 100%); b)-kdr mutation was found with a 0.95frequency. The Ace-1 mutation was also detected but at a very low frequency (≤ 5%); c) -The presence ofenzymatic activities was observed in the wild An. gambiae populations particularly GSTs andP450 oxidase which had significantly elevated levels compared to the susceptible Kisumu strain.Our research has shown that vegetable farming activity in Benin contributes to the emergence of multipleinsecticide resistance in malaria vectors. The widespread pyrethroid resistance in malaria vectorsreported in this study is a significant limitation to the use of LLINs (Long-Lasting Insecticidal Nets) as amalaria vector control strategy in many areas in southern Benin. Moreover, our findings clearly showedthe presence of metabolic resistance mechanisms in malaria vectors. These findings suggested thatmetabolic resistance may be associated with resistance to different classes of insecticides.