Exploring insecticide resistance mechanisms in three major malaria vectors from Bangui in Central African Republic

Abstract

Malaria remains the main cause of mortality and morbidity in the Central African Republic. However, the main malaria vectors remain poorly characterised, preventing the design of suitable control strategies. Here, we characterised the patterns and mechanisms of insecticide resistance in three important vectors from Bangui. Mosquitoes were collected indoors, using electrical aspirators in July 2016 in two neighborhoods at Bangui. WHO bioassays performed, using F 2 An. gambiae sensu lato (s.l.), revealed a high level of resistance to type I (permethrin) and II (deltamethrin) pyrethroids and dichlorodiphenyltrichloroethane (< 3% mortality). Molecular analysis revealed the cooccurrence of Anopheles coluzzii (56.8 %) and An. gambiae s.s. (43.2%) within the An. gambiae complex. Anopheles funestus s.s. was the sole species belonging to An. funestus group. Both kdr-w (40% of homozygotes and 60% of heterozygotes/kdr-w/wild type) and kdr-e (37.5% of heterozygotes) mutations were found in An. gambiae. Contrariwise, only the kdr-w (9.5% homozygotes and 85.7% of heterozygotes) was detected in An. coluzzii. Quantitative RT-PCR showed that CYP6M2 and CYP6P3 are not upregulated in An. coluzzii from Bangui. Analysis of the sodium channel gene revealed a reduced diversity in An. coluzzii and An. gambiae s.s. In An. funestus s.s., the pyrethroid/DDT GSTe2 L119F resistance allele was detected at high frequency (54.7%) whereas a very low frequency for Rdl was observed. Polymorphism analysis of GSTe2 and GABA receptor gene in An. funestus revealed the presence of one resistant haplotype for each gene. This study provides baseline information to help guide current and future malaria vector control interventions in CAR.

A combination of metabolic resistance and high frequency of the 1014F kdr mutation is driving pyrethroid resistance in Anopheles coluzzii population from Guinea savanna of Cameroon

“…The low genetic diversity observed in the partial fragment of the VGSC spanning exon 20, harboring the L1014F codon, suggests a restricted polymorphism of VGSC, highlighted by the very low number of haplotypes, as the 1014F allele nears fixation in this population. Our findings are consistent with previous studies reported in Central Africa [49, 60]. The fact that the predominant haplotype H3 matched with that found across Africa (H1-1014F) suggests a gene flow in An.…”

“…coluzzii is consistent with previous results in countries bordering Cameroon, e.g. northern Nigeria where a 1014F kdr mutation frequency of 83% was reported [45], and in Central African Republic, with 52.3% for the 1014F resistant allele [49].…”

“…coluzzii from Tiko, South-West region of Cameroon [7], but lower than that obtained in 2016 in An. coluzzii from Bangui, in Central African Republic [49]. However, a longitudinal survey is needed to establish the contribution of this vector to malaria transmission in this area.…”

The G119S Acetylcholinesterase (Ace-1) Target Site Mutation Confers Carbamate Resistance in the Major Malaria Vector Anopheles gambiae from Cameroon: A Challenge for the Coming IRS Implementation

“…In our knowledge, this is the first time the G119S Ace-1 mutation is clearly shown to be associated with carbamate resistance in Central African A. gambiae mosquito populations. Previous studies reporting the resistance to carbamates in A. gambiae mosquito populations from Central African countries did not detect the presence of Ace-1 G119S mutation in this region or did not establish such association [32,53,54,55,56,57].…”

High insecticide resistance in the major malaria vector Anopheles coluzzii in Chad Republic

“…coluzzii (Ngoussou colony); (ii) DNA from fully susceptible An. gambiae s.s. female (Kisumu colony); (iii) DNA from a susceptible female (SS- ace-1 ) of Central African Republic Origin [32]; and a negative control (1 μl of ddH 2 O).…”