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Background  The scale-up in the distribution of long-lasting insecticidal nets (LLINs) and indoor residual spraying has significantly reduced malaria burden and mortality. However, insecticide resistance, among other factors, is responsible for a recent rebound in malaria transmission in 2015–2016, threatening the progress so far made. As a contribution towards understanding patterns of resistance and its mechanism in the field we characterized a population of  Anopheles gambiae  ( s.l .) from Gounougou, a Guinea savanna of north/central Cameroon.    Results  Indoor collection conducted in September 2017 identified  Anopheles coluzzii  and  Anopheles arabiensis  as the unique  Anopheles  vector species, with abundances of 83 and 17%, respectively. Analysis of infection with TaqMan assays using heads/thoraces of indoor collected females of  An. coluzzii  revealed a low  Plasmodium falciparum  parasite rate of 4.7%. Bioassays conducted with female  An. coluzzii  revealed extreme resistance, with low mortalities of only 3.75 ± 1.25%, 3.03 ± 1.59% and 1.45 ± 1.45%, respectively, for permethrin, deltamethrin and DDT. In contrast, high susceptibility was obtained with the organophosphates and carbamates, with mortalities in the range of 98–100%. Synergist assays with piperonyl butoxide (PBO) recovered some susceptibility with increased mortality for permethrin to 14.88 ± 8.74%, and for deltamethrin to 32.50 ± 10.51% (~27-fold increase compared to mortalities with deltamethrin alone,  χ  2  = 29,  df  = 1,  P  < 0.0001). These correlated with the results of cone bioassays which revealed complete loss of efficacy of Olyset®Net (0% mortality) and PermaNet®2.0 (0% mortality), and the considerable loss of efficacy of Olyset®Plus (mortality of 2 ± 2%), PermaNet®3.0 side panel (mortality of 2 ± 2%) and PermaNet3.0® roof (mortality of 16 ± 5.1%). Time-course bioassays conducted with deltamethrin established a high intensity of resistance, with LT 50  of 309.09 (95% CI 253.07–393.71, Fiducial), and a resistance ratio of 93.09 compared with the fully susceptible Ngoussou laboratory colony. TaqMan genotyping revealed a high frequency of the 1014F allele (65.25%) in the  An. coluzzii  populations. Sequencing of a fragment of the voltage-gated sodium channel identified a single  An. arabiensis  female harbouring the 1014S  kdr  mutation.    Conclusions  This finding of high pyrethroid and DDT resistance in  An. coluzzii  from north-central Cameroon is a major obstacle to malaria control using pyrethroid bednets and indoor residual spraying with DDT.

parasites and vectors

A combination of metabolic resistance and high frequency of the 1014F kdr mutation is driving pyrethroid resistance in Anopheles coluzzii population from Guinea savanna of Cameroon