Sympatric Populations of the Anopheles gambiae Complex in Southwest Burkina Faso Evolve Multiple Diverse Resistance Mechanisms in Response to Intense Selection Pressure with Pyrethroids

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Résumé

Abstract: Pyrethroid resistance in the Anopheles vectors of malaria is driving an urgent search for
new insecticides that can be used in proven vector control tools such as insecticide treated nets (ITNs).
Screening for potential new insecticides requires access to stable colonies of the predominant vector
species that contain the major pyrethroid resistance mechanisms circulating in wild populations.
Southwest Burkina Faso is an apparent hotspot for the emergence of pyrethroid resistance in species
of the Anopheles gambiae complex. We established stable colonies from larval collections across
this region and characterised the resistance phenotype and underpinning genetic mechanisms.
Three additional colonies were successfully established (1 An. coluzzii, 1 An. gambiae and 1 An.
arabiensis) to add to the 2 An. coluzzii colonies already established from this region; all 5 strains are
highly resistant to pyrethroids. Synergism assays found that piperonyl butoxide (PBO) exposure was
unable to fully restore susceptibility although exposure to a commercial ITN containing PBO resulted
in 100% mortality. All colonies contained resistant alleles of the voltage gated sodium channel but
with differing proportions of alternative resistant haplotypes. RNAseq data confirmed the role of P450s,
with CYP6P3 and CYP6Z2 elevated in all 5 strains, and identified many other resistance
mechanisms, some found across strains, others unique to a particular species. These strains represent
an important resource for insecticide discovery and provide further insights into the complex genetic
changes driving pyrethroid resistance.

Mots-clés

malaria vector; insecticide resistance; insecticide treated nets; cytochrome P450s; kdr; cuticular resistance