Abstract
The massive use of insecticide-treated nets (ITNs) has drastically changed the environment for malaria vector mosquitoes, challenging their host-seeking behaviour and biting success. Here, we investigated the effect of a brief exposure to an ITN on the biting behaviour of Anopheles gambiae mosquitoes and the interaction between such behaviour and the kdr mutation that confers resistance to pyrethroids. To this aim, we developed a video assay to study the biting behaviour of mosquitoes with similar genetic background, but different kdr locus genotypes (SS i.e. homozygous susceptible, RS i.e. heterozygous and RR i.e. homozygous resistant), after a brief exposure to either control untreated nets or one of two types of pyrethroid-treated nets (deltamethrin or permethrin). In presence of untreated nets, the kdr mutation did not influence mosquito blood feeding success but caused differences in feeding and prediuresis durations and blood meal size. Exposure to deltamethrin ITN decreased the blood feeding success rate of RR and RS mosquitoes, whereas in presence of permethrin ITN, the kdr mutation increased the blood-feeding success of mosquitoes. Exposure to the two types of pyrethroid-treated nets reduced feeding duration, prediuresis duration and blood meal size of all three genotypes. Our study demonstrates a complex interaction between insecticide exposure and the kdr mutation on the biting behavior of mosquitoes, which may substantially impact malaria vector fitness and disease transmission.
Highlights
Malaria vector mosquitoes become infected by and can transmit Plasmodium spp. parasites during blood meals
We investigated whether pre-exposure to an InsecticideTreated Nets (ITNs) modulates the mosquito ability to take a blood meal by using experimental conditions that mirror the exposure to insecticide occurring when a mosquito passes through an ITN after having located a host
When comparing the biting behavior among genotypes after insecticide exposure, we found that prediuresis duration of RS mosquitoes was shorter than that of susceptible and homozygous (SS) mosquitoes after permethrin exposure (HRRS-SS = 3.82 [1.15, 12.7], supplementary Table 8)
Summary
Malaria vector mosquitoes become infected by and can transmit Plasmodium spp. parasites during blood meals. A study demonstrated that kdr homozygous resistant mosquitoes have longer contacts with ITNs than homozygous susceptible mosquitoes, which are more excited by PYR irritant effect (Chandre et al 2000). These findings indicate that insecticide treatments could affect the behaviour of malaria vectors. During the host-seeking phase and the penetration through a hole in the net, mosquitoes can be exposed to sub-lethal doses of insecticide (Diop et al 2015; Parker et al 2015, 2017) Such doses do not cause death, but can have several physiological or behavioural effects on host-seeking mosquitoes (Desneux et al 2007).
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