Distribution of acetylcholinesterase (Ace-1R) target-site G119S mutation and resistance to carbamates and organophosphates in Anopheles gambiae sensu lato populations from Cameroon

Achille Jerome Binyang,Francis Zeukeng,Billy Tene-Fossog,Yvan Fotso-Toguem,Raymond Tabue,Josiane Etang,Tatiane Assatse,Daniel Nguete Nguiffo,Charles S Wondji,Emmanuel Elanga-Ndille,Flobert Njiokou,Cyrille Ndo,Lynda Nouage

doi:10.1186/s13071-022-05174-1

Abstract

BackgroundCameroon is considering the implementation of indoor residual spraying (IRS) as a complementary measure to control malaria in the context of high pyrethroid resistance in major malaria vectors. Non-pyrethroid insecticide classes such as organophosphates and carbamates may be utilized in IRS due to widespread pyrethroid resistance. However, the success of this strategy depends on good knowledge of the resistance status of malaria vectors to carbamates and organophosphates. Here, we assessed the susceptibility profile of Anopheles gambiae sensu lato with respect to carbamates and organophosphate and the distribution of the molecular mechanism underlying resistance to these insecticides.MethodsAnopheles gambiae s.l. mosquitoes were collected from nine settings across the country and bio-assayed with bendiocarb, propoxur and pirimiphos-methyl. The Ace-1 target-site G119S mutation was genotyped using a TaqMan assay. To investigate the polymorphism in the Ace-1 gene, a region of 924 base pairs in a sequence of the gene was amplified from both live and dead females of An. gambiae exposed to bendiocarb.ResultsPirimiphos-methyl induced full mortality in An. gambiae s.l. from all study sites, whereas for carbamates, resistance was observed in four localities, with the lowest mortality rate recorded in Mangoum (17.78 ± 5.02% for bendiocarb and 18.61 ± 3.86% for propoxur) in the southern part of Cameroon. Anopheles coluzzii was found to be the predominant species in the northern tropical part of the country where it is sympatric with Anopheles arabiensis. In the localities situated in southern equatorial regions, this species was predominant in urban settings, while An. gambiae was the most abundant species in rural areas. The G119S Ace-1 target-site mutation was detected only in An. gambiae and only in the sites located in southern Cameroon. Phylogenetic analyses showed a clustering according to the phenotype.ConclusionThe occurrence of the Ace-1 target-site substitution G119S in An. gambiae s.l. populations highlights the challenge associated with the impending deployment of IRS in Cameroon using carbamates or organophosphates. It is therefore important to think about a resistance management plan including the use of other insecticide classes such as neonicotinoids or pyrrole to guarantee the implementation of IRS in Cameroon.Graphical

Highlights

Cameroon is considering the implementation of indoor residual spraying (IRS) as a complementary measure to control malaria in the context of high pyrethroid resistance in major malaria vectors
The occurrence of the Ace-1 target-site substitution G119S in An. gambiae s.l. populations highlights the challenge associated with the impending deployment of IRS in Cameroon using carbamates or organophosphates
It is important to think about a resistance management plan including the use of other insecticide classes such as neonicotinoids or pyrrole to guarantee the implementation of IRS in Cameroon

Summary

Introduction

Cameroon is considering the implementation of indoor residual spraying (IRS) as a complementary measure to control malaria in the context of high pyrethroid resistance in major malaria vectors. The World Health Organization (WHO) African Region in particular has achieved impressive reductions in its annual malaria mortality, from 840,000 deaths in 2000 to 602,000 in 2020 [2]. Despite this significant progress, malaria remains a major public health concern in sub-Saharan Africa, with countries listed among the that account for approximately 70% of the world’s malaria burden [3]. Cameroon is among the 10 African countries most affected by malaria [3] This disease remains the leading cause of morbidity and mortality in health facilities in the country. Based on the severity of the problem, the Cameroonian government has made the fight against malaria a national priority highlighted in its national strategic planning documents, in particular the Health Sector Strategy 2016–2027 [5]

Methods

Results

Discussion

Conclusion