Multiple Insecticide Resistance Target Sites in Adult Field Strains of An. Gambiae s.l. From Southeast Senegal. release_bwxgeahu3jeq7emv3qzmgsdhei

Abstract

<jats:title>Abstract</jats:title> <jats:bold>Background:</jats:bold> Malaria prevention strategies are based on the use of long-lasting insecticide-treated mosquito nets (LLINs), indoor residual spraying of insecticides (IRS) and seasonal malaria chemoprevention (SMC). The combination of these strategies with artemisinin-based combination therapy (ACTs) has led to a significant reduction in malaria cases. However, malaria remains a major public health issue in most sub-Saharan African countries. Indeed, the resistance of vectors to most WHO-approved insecticides could jeopardize vector-control strategies. This study examines insecticide resistance and associated genetic mutations among malaria vectors in southeast Senegal. <jats:bold>Methods:</jats:bold> The study was conducted in October and November 2014 in two sites in southeast Senegal. <jats:italic>An. gambiae </jats:italic>s.l. populations were sampled from Kedougou (Kedougou district) and Wassadou-Badi (Tambacounda district) and were evaluated for insecticide resistance according to WHO susceptibility tests. Specimens were 3 to 5-day-old adults raised from collected larvae. Eleven insecticides belonging to the four known classes of insecticides were assessed. Mosquito species were identified and mutations associated with insecticide resistance (<jats:italic>ace-1</jats:italic>, <jats:italic>rdl (</jats:italic>A296S or A296G<jats:italic>)</jats:italic>, <jats:italic>Vgsc</jats:italic>-<jats:italic>1014F </jats:italic>and <jats:italic>Vgsc-1014S) </jats:italic>were determined. <jats:bold>Results:</jats:bold> A total of 3,742 <jats:italic>An. gambiae </jats:italic>s.l. were exposed to insecticides (2,439 from Kedougou and 1,303 from Wassadou-Badi). In both sites, mosquitoes showed high levels of resistance to all the five pyrethroids tested (mortality rates ranged from 42.8 to 81.4% in Kedougou and 52.4 to 86.4% in Wassadou-Badi) as well as to dieldrin (67.8 and 83%) and DDT (12.7 and 55%). The mosquitoes were susceptible to pirimiphos-methyl (mortality rate 100%) and malathion (mortality rates 100% and 99% in Kedougou and Wassadou-Badi respectively). <jats:italic>An. gambiae </jats:italic>s.l. populations from Kedougou were also resistant to bendiocarb. Of the 745 <jats:italic>An. gambiae </jats:italic>s.l. genotyped <jats:italic>An. gambiae s.s.</jats:italic> (71.6%) was the predominant species, followed by <jats:italic>An. arabiensis</jats:italic> (21.7%), <jats:italic>An. coluzzii</jats:italic> (6.3%) and hybrids (<jats:italic>An</jats:italic>. <jats:italic>gambiae s.s./An. coluzzii; </jats:italic>0.4%). The <jats:italic>Vgsc</jats:italic>-1014F <jats:italic>kdr </jats:italic>mutation was widely distributed and is predominant in <jats:italic>An. gambiae </jats:italic>s.s. and <jats:italic>An. coluzzii</jats:italic> in comparison to <jats:italic>An. arabiensis</jats:italic>. <jats:italic>Vgsc</jats:italic>-1014S was present in <jats:italic>An. gambiae </jats:italic>s.l. populations in Wassadou but not in Kedougou. The <jats:italic>ace-1</jats:italic> and <jats:italic>rdl</jats:italic> mutations were more frequent in <jats:italic>An. gambiae s.s. </jats:italic>compared to <jats:italic>An. arabiensis</jats:italic> but were not detected in all populations of <jats:italic>An. coluzzii</jats:italic>.<jats:bold>Conclusion:</jats:bold> The present study demonstrates the resistance of malaria vectors to pyrethroids and organo chlorines in southeast Senegal as well as the presence of genetic mutations associated with this resistance in <jats:italic>An. gambiae </jats:italic>s.l. There was no <jats:italic>Vgsc</jats:italic>-1014S mutation in <jats:italic>An. gambiae s.s.</jats:italic> population in Kedougou. These findings are key for monitoring and managing the resistance of vectors to insecticides in this region.
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