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

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 F₂ <i>An. gambiae</i> sensu lato (s.l.), revealed a high level of resistance to type I (permethrin) and II (deltamethrin) pyrethroids and dichlorodiphenyltrichloroethane (Anopheles coluzzii (56.8 %) and <i>An. gambiae</i> s.s. (43.2%) within the <i>An. gambiae</i> complex. <i>Anopheles funestus</i> s.s. was the sole species belonging to <i>An. funestus</i> group. Both <i>kdr-w</i> (40% of homozygotes and 60% of heterozygotes/<i>kdr-w</i>/wild type) and <i>kdr-e</i> (37.5% of heterozygotes) mutations were found in <i>An. gambiae</i>. Contrariwise, only the <i>kdr-w</i> (9.5% homozygotes and 85.7% of heterozygotes) was detected in <i>An. coluzzii</i>. Quantitative RT-PCR showed that <i>CYP6M2</i> and <i>CYP6P3</i> are not upregulated in <i>An. coluzzii</i> from Bangui. Analysis of the sodium channel gene revealed a reduced diversity in <i>An. coluzzii</i> and <i>An. gambiae</i> s.s. In <i>An. funestus</i> s.s., the pyrethroid/DDT <i>GSTe2</i> L119F resistance allele was detected at high frequency (54.7%) whereas a very low frequency for <i>Rdl</i> was observed. Polymorphism analysis of <i>GSTe2</i> and <i>GABA</i> receptor gene in <i>An. funestus</i> 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.