Exploring Mechanisms of Multiple Insecticide Resistance in a Population of the Malaria Vector Anopheles funestus in Benin

Abstract

BackgroundThe insecticide resistance status of the malaria vector Anopheles funestus and the underlying resistance mechanisms remain uncharacterised in many parts of Africa, notably in Benin, West Africa. To fill this gap in our knowledge, we assessed the susceptibility status of a population of this species in Pahou, Southern Benin and investigated the potential resistance mechanisms.Methodology/Principal FindingsWHO bioassays revealed a multiple resistance profile for An. funestus in Pahou. This population is highly resistant to DDT with no mortality in females after 1h exposure to 4%DDT. Resistance was observed against the Type I pyrethroid permethrin and the carbamate bendiocarb. A moderate resistance was detected against deltamethrin (type II pyrethroids). A total susceptibility was observed against malathion, an organophosphate. Pre-exposure to PBO did not change the mortality rates for DDT indicating that cytochrome P450s play no role in DDT resistance in Pahou. No L1014F kdr mutation was detected but a correlation between haplotypes of two fragments of the Voltage-Gated Sodium Channel gene and resistance was observed suggesting that mutations in other exons may confer the knockdown resistance in this species. Biochemical assays revealed elevated levels of GSTs and cytochrome mono-oxygenases in Pahou. No G119S mutation and no altered acetylcholinesterase gene were detected in the Pahou population. qPCR analysis of five detoxification genes revealed that the GSTe2 is associated to the DDT resistance in this population with a significantly higher expression in DDT resistant samples. A significant over-expression of CYP6P9a and CYP6P9b previously associated with pyrethroid resistance was also seen but at a lower fold change than in southern Africa.ConclusionThe multiple insecticide resistance profile of this An. funestus population in Benin shows that more attention should be paid to this important malaria vector for the implementation and management of current and future malaria vector control programs in this country.

Impact of pyrethroid resistance on operational malaria control in Malawi

“…The pyrosequencing AB software was used to design three sequence-specific primers for Ace-1 and kdr mutations (the L1014F and L1014S kdr-variants are detected in the same assay). The sequences for genotyping analysis and the dispensation order for both reactions are the same as previously described (40). Target DNA fragments for kdr and Ace-1 were first amplified by PCR using the forward and biotinylated reverse primers.…”

Advances and Perspectives in the Study of the Malaria Mosquito Anopheles funestus

“…funestus [63,64,71,72]. However, a multiple insecticide resistance profile has been recently observed in Benin [74]. Insecticide resistance is an threat to effective malaria control.…”

“…Both colonies have been recurrently used in insecticide resistance studies of An. funestus [74,79,80]. Indeed, it is one of these colonies (FUMOZ), which has been elected as reference An.…”

The Role of the Conformational Dynamics of Glutathione S-Transferase Epsilon Class on Insecticide Resistance inAnopheles gambiae

“…16 Furthermore, GSTE2 gene displays the highest level of conservation among all the GSTEs in Anopheles species whereas the GSTE5 gene is evolving under positive selection. 62 The negative selection curbing AgGSTE2 sequence divergence favors its DDT dehydrochlorinase activity, the highest ever reported for any GST enzyme 13,14 On the other hand, several sites in AgGSTE5 are under positive selection: 4 residues in the N-terminal domain, where the binding of glutathione occurs (G-site), and 14 residues in the substrate-binding site (H-site). 63 The increased rate of non-similar amino acid replacements in the G-site and H-site strongly suggest that AgGSTE5 is undergoing selective pressure to express dehydrochlorinase activity.…”

“…Several studies have reported resistance to dichlorodiphenyl-trichloroethane (DDT) and other insecticides by this species. [11][12][13] It has been shown that the GST Epsilon class isoform 2 from A. gambiae (AgGSTE2) is associated to DDT resistance via two mechanisms: elevated gene expression and catalytic activity of the recombinant enzyme. 14 For this reason, AgGSTE2 is overexpressed in resistant strains and the recombinant protein is efficient at metabolizing DDT.…”