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Background  The effectiveness of Long-Lasting Insecticidal Nets and Indoor Residual Spraying in malaria vector control is threatened by vector resistance to insecticides. Knowledge of mosquito habitats and patterns of insecticide resistance would facilitate the development of appropriate vector control strategies. Therefore, we investigated  An. coluzzii  larval habitats and resistance to insecticides in the Manoka rural island area compared with the Youpwe suburban inland area, in Douala VI and II districts respectively.    Methods  Anopheline larvae and pupae were collected from open water bodies in December 2013 and April 2014 and reared until adult emergence. Two to four day old emerging females were morphologically identified as belonging to the  An. gambiae  complex and used for WHO susceptibility tests with 4 % DDT, 0.75 % permethrin, and 0.05 % deltamethrin, with or without piperonyl butoxide (PBO) synergist. Control and surviving specimens were identified down to the species using a PCR-RFLP method. Survivors were genotyped for  kdr  L1014 mutations using Hot Oligonucleotide Ligation Assay.    Results  In both study sites, ponds, residual puddles, boats, and drains were identified as the major  An. gambiae s.l.  larval habitats. A total of 1397 females ,  including 784 specimens from Manoka and 613 from Youpwe, were used for resistance testing. The two mosquito populations displayed resistance to DDT, permethrin and deltamethrin, with variable mortality rates from 1 % to 90 %. The knock-down times were also significantly increased (at least 2.8 fold). Pre-exposure of mosquitoes to PBO did not impact on their mortality to DDT, conversely the mortality rates to permethrin and deltamethrin were significantly increased (7.56 ≤ X 2  ≤ 48.63, df = 1,  p  < 0.01), suggesting involvement of P450 oxidases in pyrethroid resistance. A subsample of 400  An. gambiae s.l.  specimens including 280 control and 120 survivors from bioassays were all found to be  An. coluzzii  species. Only the  kdr  1014 F mutation was found in survivors, with 88.5 % ( N  = 76) and 75 % ( N  = 44) frequencies in Youpwe and Manoka respectively.    Conclusion  This is the first report of  An. coluzzii  resistance to insecticides in an insular area in Cameroon. Since permanent larval habitats have been identified, larval source management strategies may be trialed in this area as complementary vector control interventions.

Anopheles coluzzii larval habitat and insecticide resistance in the island area of Manoka, Cameroon