Pyrethroids are the only group of insecticides currently recommended for net treatment. Resistance monitoring is essential to investigate the susceptibility of wild populations of An. gambiae s.l. to pyrethroids. We investigated the kind of mosquito sample useful in the assessment of insecticide susceptibility tests in malaria vectors in the field conditions. Two mosquito samples were used. The first sample concerned larvae and pupae collected using the dipping method on several breeding sites and the second sample concerned female An. gambiae s.l. mosquitoes collected from window traps put on windows of rooms in districts surveyed. female An. gambiae s.l. mosquitoes were collected from March-July and August-November 2014 during the rainy season in Grand Popo, Comè, Lokossa districts selected in south-western Benin. WHO bioassays were performed with impregnated papers of permethrin 0.75% with the first sample whereas CDC bioassays were performed with stock solution of permethrin 21.5 μg per bottle with the second sample. The current study showed that although two different mosquito samples were used with two different protocols for the determination of insecticide susceptibility in malaria vectors, the susceptibility status to permethrin recorded with WHO and CDC methods were the same. Otherwise, female An. gambiae s.l. populations from Grand Popo, Comè, Lokossa were resistant to permetrhin. However, the use of female An. gambiae s.l. mosquitoes collected using the dipping method on several breeding sites may be better than using samples from window traps in the assessment of insecticide susceptibility tests in malaria vectors in field conditions.

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