Abstract
BackgroundUnderstanding the molecular basis of insecticide resistance in mosquito, such as Anopheles funestus, is an important step in developing strategies to mitigate the resistance problem. This study aims to assess the role of the GSTe2 gene in DDT resistance and determine the genetic diversity of this gene in An. funestus.MethodsGene expression analysis was performed using microarrays and PCR while the potential mutation associated with resistance was determined using sequencing.ResultsLow expression level of GSTe2 gene was recorded in Burkina-Faso samples with a fold change of 3.3 while high expression (FC 35.6) was recorded in southern Benin in Pahou (FC 35.6) and Kpome (FC 13.3). The sequencing of GSTe2 gene in six localities showed that L119F-GSTe2 mutation is almost getting fixed in highly DDT-resistant Benin (Pahou, Kpome, Doukonta) and Nigeria (Akaka Remo) mosquitoes with a low mutation rate observed in Tanongou (Benin) and Burkina-Faso mosquitoes.ConclusionThis study shows the key role of the GSTe2 gene in DDT resistant An. funestus in Benin. Polymorphism analysis of this gene across Benin revealed possible barriers to gene flow, which could impact the design and implementation of resistance management strategies in the country.
Highlights
Understanding the molecular basis of insecticide resistance in mosquito, such as Anopheles funestus, is an important step in developing strategies to mitigate the resistance problem
The use of DDT raises concerns of potential harm to the environment and human health, mainly because of the persistent and bioaccumulative nature of DDT and its potential to magnify through the food chain, it continued to be used for pest control, for which exemptions were granted by the federal government and it is still available for public health use today [5]
Analysis of glutathione-S-transferase epsilon 2 (GSTe2) polymorphism established that the L119F-Gste2 mutation is tightly associated with metabolic resistance to DDT and its geographical distribution strongly correlates with DDT resistance patterns across Africa [12]
Summary
Understanding the molecular basis of insecticide resistance in mosquito, such as Anopheles funestus, is an important step in developing strategies to mitigate the resistance problem. DDT resistance in An. gambiae can be due either to a specific detoxification mechanism (glutathione-Stransferase) or to a nerve insensitivity resulting from a modification of the target site (sodium channel). The latter, governed by the kdr gene, reduces both the knockdown and lethal effects of DDT [7]. The strong contrast in the allele frequencies of the L119F-GSTe2 frequencies despite the similar resistance profile recorded in An. funestus populations from two localities in Ghana [13] suggest that possible barriers to gene flow could exist between populations of the same country Such differences in the underlying resistance mechanisms should be taken into account when designing suitable insecticide resistance management strategies. As GSTe2 gene has been associated with DDT resistance patterns across Africa, this study aimed to investigate the role of the GSTe2 gene in DDT resistance across Benin to fill the knowledge gap by checking if this resistance is driven by the same mechanism
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