High insecticide resistance mediated by different mechanisms in Culex quinquefasciatus populations from the city of Yaound\xe9, Cameroon

Abdou Talipouo,Konstantinos Mavridis,Vasileia Balabanidou,Borel Djiappi-Tchamen,Roland Bamou,Emmanouil Alexandros Fotakis,Charles Sinclair Wondji,Parfait Awono-Ambene,Edmond Kopya,Elysée Nchoutpouen,Christophe Antonio-Nkondjio,John Vontas,Sofia Balaska,Sévilor Kekeunou

doi:10.1038/s41598-021-86850-7

Abstract

Culex mosquitoes particularly Culex quinquefasciatus are important arboviral and filariasis vectors, however despite this important epidemiological role, there is still a paucity of data on their bionomics. The present study was undertaken to assess the insecticide resistance status of Cx. quinquefasciatus populations from four districts of Yaoundé (Cameroon). All Culex quinquefasciatus populations except one displayed high resistance to bendiocarb and malathion with mortalities ranging from 0 to 89% while high resistance intensity against both permethrin and deltamethrin was recorded. Molecular analyses revealed high frequencies of the ACE-1 G119S mutation (ranging from 0 to 33%) and kdr L1014F allele (ranging from 55 to 74%) in all Cx. quinquefasciatus populations. Significant overexpression was detected for cytochrome P450s genes CYP6AA7 and CYP6Z10, as well as for Esterase A and Esterase B genes. The total cuticular hydrocarbon content, a proxy of cuticular resistance, was significantly increased (compared to the S-lab strain) in one population. The study confirms strong insecticide resistance mediated by different mechanisms in Cx. quinquefasciatus populations from the city of Yaoundé. The expansion of insecticide resistance in Culex populations could affect the effectiveness of current vector control measures and stress the need for the implementation of integrated vector control strategies in urban settings.

Highlights

Culex mosquitoes Culex quinquefasciatus are important arboviral and filariasis vectors, despite this important epidemiological role, there is still a paucity of data on their bionomics
The An. gambiae Kisumu strain was susceptible to all insecticides whereas the Cx. quinquefasciatus S-lab reference strains showed increase tolerance to permethrin and deltamethrin and high resistance to DDT
Culex quinquefasciatus mosquitoes are predominant in most cities across Sub-Saharan Africa and they are of major epidemiological significance as vectors of important diseases like West Nile Virus and filariasis, little is known about their susceptibility to insecticides and the presence and frequency of previously characterised resistance alleles in the local populations

Summary

Introduction

Culex mosquitoes Culex quinquefasciatus are important arboviral and filariasis vectors, despite this important epidemiological role, there is still a paucity of data on their bionomics. Culex species and mosquitoes of the Culex pipiens complex, are considered vectors of several diseases such as Lymphatic filariasis, West Nile Virus, Japanese Encephalitis, Saint Louis Encephalitis, Dengue and Rift Valley Fever with some being fatal in the absence of treatment and others causing lifelong disabilities and impairment[1]. In addition to their role as vectors, Culex species are responsible for a high nuisance problem[2,3]. Mutation L1014F, which upon homozygosity has been associated with operationally significant resistant phenotypes and striking ones, when in combination with P450 metabolic r esistance[21] has been recorded in Cx. quinquefasciatus populations from Benin, Cameroon and Zambia[8,22,23] at allele frequencies ranging from 20 to 60%24

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