Abstract: Objective　To analyze the density, distribution and insecticide resistance of Aedes albopictus in Ningbo City in 2021, so as to provide insights into formulation of dengue fever control strategies. Methods　Four administrative villages were randomly selected from each county (district) in Ningbo City from April to November, 2021, to investigate the indoor population density of Aedes larvae, and the Breteau index (BI) was calculated. The population density of adult mosquitoes was investigated in residential areas, parks/bamboo forests, waste tire stacking sites/waste stations/construction sites in each county (district). On June 2021, larvae of the natural strain A. albopictus were collected from epidemic sites of dengue fever in Ningbo City in 2018, and raised in laboratory. Then, larvae and female mosquitoes without blood feeding were selected for insecticide resistance bioassays, while insecticide⁃sensitive strains of A. albopictus served as controls. The resistance of A. albopictus larvae to deltamethrin, beta⁃cypermethrin, propoxur, temephos and dichlorvos using the impregnation method, and the medium lethal concentration (LC50) and resistance ratio (RR) were calculated. The resistance of adult A. albopictus to beta⁃cypermethrin, permethrin, deltamethrin, propoxur and malathion was determined using the tube bioassay, and the mosquito mortality was calculated. Results　A total of 10 072 small water containers from 9 935 households were investigated in Ningbo City in 2021, and there were 1 276 containers with Aedes larvae detected, with an average BI of 12.89. Totally 1 422 mosquito nets were allocated and 954 female A. albopictus were captured, with an average net trapping index of 1.34 mosquitoes/(net·hour). Both larval and adult A. albopictus mosquitoes were found from April to November, and the density of larval A. albopictus peaked in September (BI = 21.21), while the density of adult A. albopictus peaked in August, with a net trapping index of 2.38 mosquitoes/(net ·hour). The LC50 values of deltamethrin, beta⁃cypermethrin, propoxur, temephos and dichlorvos were 0.017 4, 0.000 9, 0.364 1, 0.038 1 mg/L and 0.001 6 mg/L against larvae of natural strains of A. albopicchus, with RRs of 49.66, 25.53, 9.65, 2.24 and 6.06, and the mortality rates of adult mosquitoes were 66.00% (66/100), 69.39% (68/98), 25.00% (25/100), 98.97% (96/97) and 100.00% (98/98) 24 hours post⁃treatment with 0.08% beta⁃cypermethrin, 0.03% deltamethrin, 0.4% permethrin, 0.05% propoxur, and 0.5% malathion for 24 h, respectively. Conclusions　A. albopictus is widely distributed in Ningbo City, with a high population density and presents high⁃level resistance to common pyrethroid insecticides. The population density and insecticide resistance of A. albopictus requires to be reinforced.

Key words: Aedes albopictus, Density surveillance, Dengue fever, Insecticide resistance, Ningbo City

摘要： 目的　分析2021年宁波市白纹伊蚊密度、分布和杀虫剂抗性，为制定登革热防控策略提供科学依据。方法　2021年4—11月，于宁波市各县（市、区）均随机选取4个行政村入户调查伊蚊幼虫种群密度，计算布雷图指数（Breteau Index，BI）；于各县（市、区）分别选择居民区、公园/竹林、旧轮胎堆放地/废品站/工地等3类生境开展成蚊种群密度调查。2021年6月，于2018年宁波市登革热疫点采集自然品系白纹伊蚊幼虫，经实验室饲养后，分别选取幼虫和未吸血雌蚊开展抗药性实验，对照组蚊虫为白纹伊蚊杀虫剂敏感品系。其中幼虫以浸渍法测定对溴氰菊酯、高效氯氰菊酯、残杀威、双硫磷和敌敌畏抗药性，计算半数致死浓度（medium lethal concentration，LC50）和抗性倍数（resistance ratio，RR）；成虫以接触筒法测定对高效氯氰菊酯、氯菊酯、溴氰菊酯、残杀威和马拉硫磷抗药性，计算死亡率。结果　2021年宁波市累计调查9 935户10 072个小型积水容器，其中伊蚊幼虫阳性容器1 276个，平均BI为12.89；共布帐1 422顶，捕获雌性白纹伊蚊954只，平均帐诱指数为1.34只/（顶·h）。4—11月白纹伊蚊幼虫与成蚊均有发现，其中9月为幼虫密度峰值（BI = 21.21）、8月为成蚊密度峰值，帐诱指数2.38只/（顶·h）。宁波市自然品系白纹伊蚊幼虫对溴氰菊酯、高效氯氰菊酯、残杀威、双硫磷和敌敌畏LC50值分别为0.017 4、0.000 9、0.364 1、0.038 1 mg/L和0.001 6 mg/L，抗性倍数分别为49.66、25.53、9.65、2.24和6.06；成蚊接触0.08%高效氯氰菊酯、0.03%溴氰菊酯、0.4%氯菊酯、0.05%残杀威和0.5%马拉硫磷24 h死亡率分别为66.00%（66/100）、69.39%（68/98）、25.00%（25/100）、98.97%（96/97）和100.00%（98/98）。结论　宁波市白纹伊蚊分布广泛、种群密度较高，对常用拟除虫菊酯类杀虫剂存在较高抗药性，应进一步加强其种群密度及抗药性监测。

关键词: 白纹伊蚊, 密度监测, 登革热, 杀虫剂抗性, 宁波市