Abstract
BackgroundMosquitoes of the Culex pipiens complex, competent vectors for West Nile virus (WNV) and Rift Valley fever virus (RVFV) are widely targeted by insecticide treatments. The intensive application of chemical insecticides led to the development of resistance in many insects including Culex pipiens mosquitoes. The absence of data on resistance mechanisms in Morocco allow us to assess the levels of lambda-cyhalothrin resistance and the frequency of the mutated gene L1014F kdr in different forms of Cx. pipiens complex from three regions of Morocco.MethodsMosquito adults were reared from immature stages collected in three different regions in Morocco (Tangier, Casablanca and Marrakech). Standard WHO insecticide susceptibility tests were conducted on adults emerged from collected larvae. Specimens were identified as belonging to the Culex pipiens complex using a multiplex PCR assay with diagnostic primers designed from the flanking region of microsatellite CQ11. Identified mosquitoes were then tested for the presence of the L1014F kdr mutation using PCR assay.ResultsOur results showed that 21% of the tested population has a resistance to lambda-cyhalothrin. The molecular identification of survivors shows that 43% belonged to the Cx. pipiens pipiens and only 9.5% to the Cx. pipiens molestus form. On the other hand, 416 specimens were screened for the L1014F kdr mutation. L1014F mutation was detected in different forms of Cx. pipiens in different sites. The frequency of L1014F mutation was similar between the Cx. pipiens pipiens form and hybrid form, while it was lower in the Cx. pipiens molestus form. The presence of the L1014F kdr allele was significantly associated with resistance to lambda-cyhalothrin in Cx. pipiens pipiens (P < 0.0001) and hybrid form (P < 0.0001).ConclusionResistance to lambda-cyhalothrin of Cx. pipiens populations appears to be largely due to the L1014F kdr mutation. To our knowledge, the frequencies of L1014F kdr mutation are examined for the first time in natural populations of the Culex pipiens complex in Morocco. These findings will provide important information to propose more adapted vector control measures towards this mosquito species, potential vector of arboviruses.
Highlights
Mosquitoes of the Culex pipiens complex, competent vectors for West Nile virus (WNV) and Rift Valley fever virus (RVFV) are widely targeted by insecticide treatments
Knowing that insecticide resistance remains a global issue for the control of mosquito-borne diseases, this study aims to investigate the L1014F kdr mutation frequencies in different forms of Culex pipiens complex collected in three regions in Morocco: Tangier, Casablanca and Marrakech
Insecticide susceptibility and identification of Culex pipiens forms Twenty-four hours after exposure of 100 Cx. pipiens collected in Casablanca to lambda-cyhalothrin, 79% of exposed adults died
Summary
Mosquitoes of the Culex pipiens complex, competent vectors for West Nile virus (WNV) and Rift Valley fever virus (RVFV) are widely targeted by insecticide treatments. Mosquitoes of the Culex pipiens complex are potential vectors of Rift Valley fever virus (RVFV) and West Nile virus (WNV). RVFV is a Phlebovirus of the family Bunyaviridae, considered as an emerging zoonotic vector-borne disease representing a threat to animal and human health, and livestock production mainly in subSaharan Africa [1]. Resistance to kd is caused by a mutation L1014F, the substitution of a leucine at position 1,014 by a phenylalanine conferring the kdr phenotype [19], leading to a lower sensitivity of receptors to these insecticides and modifying the potential action of the channel [18, 20]
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