The spread of Ace-1R mutation that confers carbamate and organophosphate resistance in Anopheles gambiae s.l. is a critical issue for malaria vector control. The aim of this study was to investigate the seasonal variation of the Ace-1R mutation in A. gambiae s. l populations. The mosquitoes analyzed were collected by human landing catches (HLC) in five districts in the department of Atacora from May 2011 to June 2013. The collection was carried out twice a month by adult volunteers. They caught any mosquitoes that landed on their legs with an aspirator from 7.00 p.m to 6.00 a.m. Anopheles mosquitoes were morphologically identified and polymerase chain reaction (PCR) assays were run to determine the members of the A. gambiae complex, as well as phenotypes for insensitive acetylcholinesterase (AChE1) due to the Ace-1R mutation. This study shows that A. gambiae s. s. and Anopheles coluzzii occurred in sympatry in the Atacora region. However, A. gambiae s. s. was predominant during the rainy season, while A. coluzzii was predominant during the dry season. Moreover, the Ace-1R mutation was detected either in A. gambiae s. s. or in A. coluzzii. Results showed a dramatical increase in Ace-1R allelic frequency during the dry season. The present study provides useful information on the seasonal variation of Ace-1R allelic frequency in A. gambiae populations from Atacora. It showed that Ace-1R allelic frequency has increased in rainy season which can be explained by the various selective insecticide pressures on A. gambiae during this season that consist of agricultural practices and indoor residual spraying using bendiocarb.
Key words: Anopheles gambiae Ace-1R, resistance, seasonal, Atacora, Benin.
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