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Background  Insecticide-based vector control, which comprises use of insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS), is the key method to malaria control in Madagascar. However, its effectiveness is threatened as vectors become resistant to insecticides. This study investigated the resistance status of malaria vectors in Madagascar to various insecticides recommended for use in ITNs and/or IRS.    Methods  WHO tube and CDC bottle bioassays were performed on populations of  Anopheles gambiae  ( s.l. ),  An .  funestus  and  An .  mascarensis.  Adult female  An .  gambiae  ( s.l. ) mosquitoes reared from field-collected larvae and pupae were tested for their resistance to DDT, permethrin, deltamethrin, alpha-cypermethrin, lambda-cyhalothrin, bendiocarb and pirimiphos-methyl. Resting  An .  funestus  and  An .  mascarensis  female mosquitoes collected from unsprayed surfaces were tested against permethrin, deltamethrin and pirimiphos-methyl. The effect on insecticide resistance of pre-exposure to the synergists piperonyl-butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) also was assessed. Molecular analyses were done to identify species and determine the presence of knock-down resistance ( kdr ) and acetylcholinesterase resistance ( ace-1    R    )  gene mutations.    Results    Anopheles funestus  and  An .  mascarensis  were fully susceptible to permethrin, deltamethrin and pirimiphos-methyl.  Anopheles gambiae  ( s.l. ) was fully susceptible to bendiocarb and pirimiphos-methyl. Among the 17  An .  gambiae  ( s.l. ) populations tested for deltamethrin, no confirmed resistance was recorded, but suspected resistance was observed in two sites.  Anopheles gambiae  ( s.l. ) was resistant to permethrin in four out of 18 sites (mortality 68–89%) and to alpha-cypermethrin (89% mortality) and lambda-cyhalothrin (80% and 85%) in one of 17 sites, using one or both assay methods. Pre-exposure to PBO restored full susceptibility to all pyrethroids tested except in one site where only partial restoration to permethrin was observed. DEF fully suppressed resistance to deltamethrin and alpha-cypermethrin, while it partially restored susceptibility to permethrin in two of the three sites. Molecular analysis data suggest absence of  kdr  and  ace-1    R   gene mutations.    Conclusion  This study suggests involvement of detoxifying enzymes in the phenotypic resistance of  An .  gambiae  ( s.l. ) to pyrethroids. The absence of resistance in  An .  funestus  and  An .  mascarensis  to pirimiphos-methyl and pyrethroids and in  An .  gambiae  ( s.l. ) to carbamates and organophosphates presents greater opportunity for managing resistance in Madagascar.    Electronic supplementary material  The online version of this article (doi:10.1186/s13071-017-2336-9) contains supplementary material, which is available to authorized users.

parasites and vectors

Insecticide resistance status of three malaria vectors, Anopheles gambiae (s.l.), An. funestus and An. mascarensis, from the south, central and east coasts of Madagascar