Insecticide Resistance Profiling of Anopheles coluzzii and Anopheles gambiae Populations in the Southern Senegal: Role of Target Sites and Metabolic Resistance Mechanisms.

Oumou K Gueye,Abdoulaye K Dia,Mouhamed B Faye,Charles S Wondji,El Hadji A Niang,Daniel N Nguiffo,Ibrahima Dia,Leon M J Mugenzi,Murielle J Wondji,Oumar Gaye,Magellan Tchouakui,Ousmane Faye,Abdoulaye Diabate,Lassana Konaté,Frederic Tripet,Amblat A Ahmed

doi:10.3390/genes11121403

Abstract

The emergence and spread of insecticide resistance among the main malaria vectors is threatening the effectiveness of vector control interventions in Senegal. The main drivers of this resistance in the Anopheles gambiae complex (e.g., An. gambiae and Anopheles coluzzii) remains poorly characterized in Senegal. Here we characterized the main target site and metabolic resistances mechanisms among the An. gambiae and An. coluzzii populations from their sympatric and allopatric or predominance area in Senegal. Larvae and pupae of An. gambiae s.l. were collected, reared to adulthood, and then used for insecticides susceptibility and synergist assays using the WHO (World Health Organisation) test kits for adult mosquitoes. The TaqMan method was used for the molecular characterization of the main target site insecticide resistance mechanisms (Vgsc-1014F, Vgsc-1014S, N1575Y and G119S). A RT-qPCR (Reverse Transcriptase-quantitative Polymerase Chaine Reaction) was performed to estimate the level of genes expression belonging to the CYP450 (Cytochrome P450) family. Plasmodium infection rate was investigated using TaqMan method. High levels of resistance to pyrethroids and DDT and full susceptibility to organophosphates and carbamates where observed in all three sites, excepted a probable resistance to bendiocarb in Kedougou. The L1014F, L1014S, and N1575Y mutations were found in both species. Pre-exposure to the PBO (Piperonyl butoxide) synergist induced a partial recovery of susceptibility to permethrin and full recovery to deltamethrin. Subsequent analysis of the level of genes expression, revealed that the CYP6Z1 and CYP6Z2 genes were over-expressed in wild-resistant mosquitoes compared to the reference susceptible strain (Kisumu), suggesting that both the metabolic resistance and target site mutation involving kdr mutations are likely implicated in this pyrethroid resistance. The presence of both target-site and metabolic resistance mechanisms in highly pyrethroid-resistant populations of An. gambiae s.l. from Senegal threatens the effectiveness and the sustainability of the pyrethroid-based tools and interventions currently deployed in the country. The Kdr-west mutation is widely widespread in An. coluzzii sympatric population. PBO or Duo nets and IRS (Indoor Residual Spraying) with organophosphates could be used as an alternative measure to sustain malaria control in the study area.

Highlights

The control of malaria vector in Africa relies mainly on the two core insecticide-based interventions: Long-Lasting Insecticide Nets (LLINs) and Indoor Residual Spraying (IRS) [1]
An. gambiae complex, An. arabiensis was predominant in Fatick (81.68 vs. 65.17%) and was present in Kedougou (16.36 vs. 7.46%) and Tambacounda (28.94 vs. 15.64%)
In this study only CYP6Z1 and CYP6Z2 have been differentially expressed between field-resistant mosquitoes and the susceptible strain suggesting a potential implication of these two genes in the pyrethroid resistance observed. This findings of high pyrethroid and DDT resistance in An. gambiae and An. coluzzii from Senegal is a major obstacle to malaria control using pyrethroid or DDT-based tools

Summary

Introduction

The control of malaria vector in Africa relies mainly on the two core insecticide-based interventions: Long-Lasting Insecticide Nets (LLINs) and Indoor Residual Spraying (IRS) [1]. Given the heavy reliance on pyrethroid-based strategies for malaria vector control, the spread across sub-Saharan Africa of the resistance to this class of insecticide threatens the sustainability of current and future vector control interventions. Two main types of mechanisms are involved in the resistance of An. gambiae to the principal classes of insecticide use in the public health sector: the target-site insensitivity [3,4] and the metabolic activity of detoxification enzyme families such as cytochrome P450s, glutathione S-transferases and esterases [5]. The Vgsc-1014F and Vgsc-1014S mutations, respectively known as kdr-west and kdr-east [6,7], are among the most widespread target-site insecticide resistance mechanisms found among the natural population of An. coluzzii and An. gambiae [8] across the Western and Eastern

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Discussion

Conclusion