Multiple insecticide resistance and Plasmodium infection in the principal malaria vectors Anopheles funestus and Anopheles gambiae in a forested locality close to the Yaoundé airport, Cameroon.

Francis Nongley Nkemngo ,Romuald Agonhossou,Murielle J Wondji,Cyrille Ndo,Ebai Terence,Steffen Borrmann,Yudi T Pinilla,Helen Irving,Williams Tchapga,Charles S Wondji,Nguiffo D Nguete,Abdoulaye Niang,Leon M J Mugenzi,Francine Ntoumi,Micareme Tchoupo,Luc Djogbénou ,Félix Koukouikila-Koussounda ,Romaric Akoton ,Stephen Mbigha Ghogomu ,Jacques Dollon Mbama Ntabi ,Ayôla Akim Adegnika ,Terence S Boussougou-Sambe

doi:10.12688/wellcomeopenres.15818.2

Abstract

Background: Reducing the burden of malaria requires better understanding of vector populations, particularly in forested regions where the incidence remains elevated. Here, we characterized malaria vectors in a locality near the Yaoundé international airport, Cameroon, including species composition, abundance, Plasmodium infection rate, insecticide resistance profiles and underlying resistance mechanisms. Methods: Blood-fed adult mosquitoes resting indoors were aspirated from houses in April 2019 at Elende, a locality situated 2km from the Yaoundé-Nsimalen airport. Female mosquitoes were forced to lay eggs to generate F 1 adults. Bioassays were performed to assess resistance profile to the four insecticides classes. The threshold of insecticide susceptibility was defined above 98% mortality rate and mortality rates below 90% were indicative of confirmed insecticide resistance. Furthermore, the molecular basis of resistance and Plasmodium infection rates were investigated. Results: Anopheles funestus s.s. was the most abundant species in Elende (85%) followed by Anopheles gambiae s.s. (15%) with both having similar sporozoite rate. Both species exhibited high levels of resistance to the pyrethroids, permethrin and deltamethrin (<40% mortality). An. gambiae s.s. was resistant to DDT (9.9% mortality) and bendiocarb (54% mortality) while susceptible to organophosphate. An. funestus s.s. was resistant to dieldrin (1% mortality), DDT (86% mortality) but susceptible to carbamates and organophosphates. The L119F-GSTe2 resistance allele (8%) and G119S ace-1 resistance allele (15%) were detected in An. funestus s.s. and An. gambiae s.s., respectively . Furthermore, the high pyrethroid/DDT resistances in An. gambiae corresponded with an increase frequency of 1014F kdr allele (95%). Transcriptional profiling of candidate cytochrome P450 genes reveals the over-expression of CYP6P5, CYP6P9a and CYP6P9b. Conclusion: The resistance to multiple insecticide classes observed in these vector populations alongside the significant Plasmodium sporozoite rate highlights the challenges that vector control programs encounter in sustaining the regular benefits of contemporary insecticide-based control interventions in forested areas.

Highlights

Malaria is the major vector-borne disease globally and a leading public health problem[1]
In order to facilitate and reinforce the National Malaria Control Program in their efforts to implementing sustainable and efficacious vector control interventions, this study investigated the entomological component of malaria transmission in a peri-urban setting within the forested region of Cameroon
Assessment of bed net efficacy using cone assay Due to the low abundance of Anopheles gambiae s.s., in this locality, we examined the efficacy of bed nets approved by World Health Organization (WHO) against the Elende An. funestus s.s. population

Summary

Introduction

Malaria is the major vector-borne disease globally and a leading public health problem[1]. There was a reported increase in malaria victims in 2018 compared with the previous years in ten African countries scoring the highest burden of the disease[1] To this effect, the WHO Global Technical Strategy for Malaria (2016–2030) outlines a pathway for malaria control and elimination and designates a target for a 90% reduction in global malaria mortality rates by 2030 relative to a 2015 baseline[2]. The WHO Global Technical Strategy for Malaria (2016–2030) outlines a pathway for malaria control and elimination and designates a target for a 90% reduction in global malaria mortality rates by 2030 relative to a 2015 baseline[2] In this vein, the recent certification of Algeria and Argentina as malaria-free countries by the World Health Organization (WHO) has been a historic achievement for universal health coverage, and serving as a model in demonstrating the feasibility of malaria elimination in the Afro-tropical region[1]. Conclusion: The resistance to multiple insecticide classes observed in these vector populations alongside the significant Plasmodium sporozoite rate highlights the challenges that vector control programs encounter in sustaining the regular benefits of contemporary insecticide-based control interventions in forested areas

Methods

Results

Discussion

Conclusion