Abstract
BackgroundExisting mechanisms of insecticide resistance are known to help the survival of mosquitoes following contact with chemical compounds, even though they could negatively affect the life-history traits of resistant malaria vectors. In West Africa, the knockdown resistance mechanism kdrR (L1014F) is the most common. However, little knowledge is available on its effects on mosquito life-history traits. The fitness effects associated with this knockdown resistance allele in Anopheles gambiae sensu stricto (s.s.) were investigated in an insecticide-free laboratory environment.MethodsThe life-history traits of Kisumu (susceptible) and KisKdr (kdr resistant) strains of An. gambiae s.s. were compared. Larval survivorship and pupation rate were assessed as well as fecundity and fertility of adult females. Female mosquitoes of both strains were directly blood fed through artificial membrane assays and then the blood-feeding success, blood volume and adult survivorship post-blood meal were assessed.ResultsThe An. gambiae mosquitoes carrying the kdrR allele (KisKdr) laid a reduced number of eggs. The mean number of larvae in the susceptible strain Kisumu was three-fold overall higher than that seen in the KisKdr strain with a significant difference in hatching rates (81.89% in Kisumu vs 72.89% in KisKdr). The KisKdr larvae had a significant higher survivorship than that of Kisumu. The blood-feeding success was significantly higher in the resistant mosquitoes (84%) compared to the susceptible ones (34.75%). However, the mean blood volume was 1.36 µL/mg, 1.45 µL/mg and 1.68 µL/mg in Kisumu, homozygote and heterozygote KisKdr mosquitoes, respectively. After blood-feeding, the heterozygote KisKdr mosquitoes displayed highest survivorship when compared to that of Kisumu.ConclusionsThe presence of the knockdown resistance allele appears to impact the life-history traits, such as fecundity, fertility, larval survivorship, and blood-feeding behaviour in An. gambiae. These data could help to guide the implementation of more reliable strategies for the control of malaria vectors.
Highlights
Existing mechanisms of insecticide resistance are known to help the survival of mosquitoes following contact with chemical compounds, even though they could negatively affect the life-history traits of resistant malaria vectors
Insecticide resistance to pyrethroids and other classes of insecticides has been reported in An. gambiae, the main malaria vector in several African countries [8,9,10,11,12,13,14]
In order to investigate the role of kdrR (L1014F) allele in An. gambiae s.s. blood-feeding behaviour, heterozygote [kdrRS]-resistant mosquitoes were obtained by crossing Kisumu females [kdrSS] with KisKdr males [kdrRR] and Kisumu males with KisKdr females encoded F1-1 (♀Kisumu X ♂KisKdr) and F1-2 (♂Kisumu X ♀KisKdr), respectively
Summary
Existing mechanisms of insecticide resistance are known to help the survival of mosquitoes following contact with chemical compounds, even though they could negatively affect the life-history traits of resistant malaria vectors. In most regions in sub-Saharan Africa, mosquito species including Anopheles gambiae sensu stricto (s.s.), Anopheles arabiensis, Anopheles coluzzii, and Anopheles funestus are the main vectors that transmit malaria parasites [3,4,5]. In An. gambiae s.s., mutations related to pyrethroids and dichlorodiphenyltrichloroethane (DDT) resistance are located mainly at codon 1014 within the transmembrane segment 6 of domain II in the Voltagegated sodium channel (Vgsc) gene. These mutations lead to a change of leucine to either phenylalanine (L1014F) or serine (L1014S) [21, 22]. Little is known about the fitness cost induced by this homozygous resistance allele in the malaria vector An. gambiae
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