BACKGROUND: Pathogens that reproduce or develop in mosquitoes can transmit several diseases, endanger human health, and overwhelm health systems. Synthetic pyrethroids are the most widely used insecticides against adult mosquitoes, but their widespread use has led to resistance. The adenosine triphosphate (ATP)-binding cassette (ABC) transporters are involved in the resistance monitoring of insects, but their role and underlying mechanisms in insecticide resistance have not been fully elucidated. In the present study, we identified ABC transporter genes in Culex pipiens and investigated their role in the development of insecticide resistance.
RESULTS: We identified 63 ABC transporter genes in Cx. pipiens and classified them as per the ABC transporter subfamilies. We also performed phylogenetic analysis. The knockdown rate of the mosquitoes orally fed with the ABC transporter inhibitor verapamil increased after deltamethrin treatment compared with that of the control group. Several genes from the ABCB, ABCC, and ABCG subfamilies were highly expressed in resistant mosquitoes. Immunofluorescence analysis revealed that ABCG6032427 was expressed in the head, chest, abdomen, wings, and legs, and the expression was the highest in the legs. Subsequently, knockdown of ABCG6032427 using RNA interference (RNAi) increased the sensitivity of the mosquitoes to deltamethrin, and scanning and transmission electron microscopy revealed that ABCG6032427 knockdown reduced cuticle thickness and the cuticle became loose and irregular.
CONCLUSIONS: ABCG6032427 may modulate cuticle thickness and structure, thus play an important role in the development of deltamethrin resistance in mosquitoes. Thus, it could be a potential target for deltamethrin resistance management in Cx. pipiens. © 2023 Society of Chemical Industry.

OBJECTIVE: To investigate the distribution and density of Culex mosquito populations and the resistance of Culex pipiens pallens to insecticides in Jiangsu Province in 2018 and 2019.
METHODS: During the period from June to October in 2018 and 2019, six counties (districts, cities) were sampled in southern, northern and central Jiangsu Province as surveillance sites. The density of Culex mosquitoes was measured overnight using the light trapping technique. In addition, Culex pipiens pallens mosquitoes were collected from Hai\'an of Nantong City and Yandu District of Yancheng City, central Jiangsu Province, and the sensitivity of female first filial generations to dichlorodiphenyltrichloroethane (DDT), malation, proposur, beta cypermethrin and deltamethrin was tested using the standard WHO insecticide susceptibility test assay.
RESULTS: A total of 104 423 Culex mosquitoes were captured in six surveillance sites of Jiangsu Province in 2018 and 2019, and Culex quinquefasciatus (49.11%), Culex pipiens pallens (28.38%), and Culex tritaeniorhynchus (21.04%) were predominant species. The density of Culex mosquitoes started to increase since early June, peaked in July and tended to be low in late October. Culex pipiens pallens mosquitoes captured from Hai\'an was susceptible to malation, while those from Yandu District were moderately resistant to malation. Culex pipiens pallens mosquitoes from both Yandu and Hai\'an were moderately resistant to proposur, and were resistant to DDT, beta cypermethrin and deltamethrin.
CONCLUSIONS: Culex quinquefasciatus, Culex pipiens pallens and Culex tritaeniorhynchus are predominant Culex species in Jiangsu Province. Culex pipiens pallens is resistant to DT, beta cypermethrin and deltamethrin in central Jiangsu Province.
［摘要］ 目的 了解2018—2019年江苏省库蚊种群分布、密度变化及淡色库蚊对杀虫剂的抗性水平。方法 2018—2019年6—10月, 选择江苏省苏南、苏北和苏中6个县 (市、区) 作为监测点, 采用全通宵诱蚊灯法调查库蚊种群密度。采集苏中地区南通市海安市和盐城市盐都区淡色库蚊, 采用WHO推荐的接触筒强迫接触法测定子1代雌性淡色库蚊对二氯二苯三氯乙烷 (dichlorodiphenyltrichloroethane, DDT)、马拉硫磷、残杀威、高效氯氰菊酯和溴氰菊酯5种杀虫剂的敏感性。结果 2018—2019年在江苏省6个监测点累计库蚊104 423只, 蚊种以致倦库蚊、淡色库蚊和三带喙库蚊为主, 分别占49.11%、28.38%和21.04%; 库蚊种群密度从6月初开始升高, 7月左右达到峰值, 10月下旬趋近于低值。海安市淡色库蚊对马拉硫磷抗性级别为敏感, 盐都区淡色库蚊对马拉硫磷抗性级别为初步抗性; 盐都区、海安市淡色库蚊对残杀威抗性级别均为初步抗性; 盐都区、海安市淡色库蚊对DDT、高效氯氰菊酯、溴氰菊酯抗性级别均为抗性。结论 江苏省库蚊种群以致倦库蚊、淡色库蚊、三带喙库蚊为主; 苏中地区淡色库蚊已对DDT、高效氯氰菊酯和溴氰菊酯产生抗性。.