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Background  Several studies were carried out in experimental hut station in areas surrounding the city of Bouaké, after the crisis in Côte d’Ivoire. They reported increasing resistance levels to insecticide for malaria transmiting mosquitoes. The present work aims to evaluate the current resistance level of  An. gambiae   (  s.l .) in rural and urban areas in the city of Bouaké.    Methods  Larvae of  Anopheles gambiae  ( s.l. ) were collected from five different study sites and reared to adult stages. The resistance status was assessed using the WHO bioassay test kits for adult mosquitoes, with eight insecticides belonging to pyrethroids, organochlorines, carbamates and organophosphates classes. Molecular assays were performed to identify the molecular forms of  An. gambiae  ( s.l. ), the L1014F  kdr  and the  ace-1R  alleles in individual mosquitoes. The synergist PBO was used to investigate the role of enzymes in resistance. Biochemical assays were performed to detect potential increased activities in mixed function oxidase (MFO) levels, non-specific esterases (NSE) and glutathione S-transferases (GST).    Results  High resistance levels to pyrethroids, organochlorines, and carbamates were observed in  Anopheles gambiae  ( s.l. ) from Bouaké. Mortalities ranged between 0 and 73% for the eight tested insecticides. The pre-exposure to PBO restored full or partial susceptibility to pyrethroids in the different sites. The same trend was observed with the carbamates in five sites, but to a lesser extent. With DDT, pre-exposure to PBO did not increase the mortality rate of  An. gambiae  ( s.l. ) from the same sites. Tolerance to organophosphates was observed. An increased activity of NSE and higher level of MFO were found compared to the Kisumu susceptible reference strain. Two molecular forms, S form [( An. gambiae  ( s.s )] and M form ( An. coluzzi ) were identified. The  kdr  allele frequencies vary from 85.9 to 99.8% for  An. gambiae  ( s.s. ) and from 81.7 to 99.6% for  An. coluzzii . The  ace-1R  frequencies vary between 25.6 and 38.8% for  An. gambiae  ( s.s .) and from 28.6 to 36.7% for  An. coluzzii.Conclusion  Resistance to insecticides is widespread within both  An. gambiae  ( s.s. ) and  An. coluzzii . Two mechanisms of resistance, i.e. metabolic and target-site mutation seemed to largely explain the high resistance level of mosquitoes in Bouaké. Pyrethroid resistance was found exclusively due to the metabolic mechanism.

The current insecticide resistance status of Anopheles gambiae (s.l.) (Culicidae) in rural and urban areas of Bouaké, Côte d’Ivoire