Objective To grasp the resistance levels of Aedes albopictus to commonly used insecticides and their trends in Fengxian district, Shanghai, China, and to provide a scientific basis for the protection against vectors and the prevention and control of dengue fever in the major urban activities. Methods The larval dipping method recommended by the World Health Organization was used to determine the insecticide resistance of Ae. albopictus larvae. Results In 2015, 2018, and 2019, the Ae. albopictus larvae showed varying degrees of resistance to three insecticides, temephos, deltamethrin, and beta-cypermethrin, and the resistance coefficient overall showed an upward trend first and then a downward trend. In recent 5 years, the overall level of resistance to temephos has been lower than that to deltamethrin and beta-cypermethrin, which remained at a low level from 2015 and 2018 and decreased to a sensitive level (resistance ratio 1.25) in 2019; the resistance to deltamethrin was highest in 2018, reaching a high resistance level (resistance ratio 68.75), and showing a fluctuating trend from medium to high and then to medium resistance; the resistance to beta-cypermethrin remained at a medium level from 2015 and 2018, and dropped to a low level (resistance ratio 7.00) in 2019. In 2019, the insecticides that controlled mosquito larvae were mainly organophosphates, of which the dose of temephos accounted for 33.87% of the total dose of insecticides used; the insecticides that controlled adult mosquitoes were mainly pyrethroids and carbamates, of which the doses of beta-cyfluthrin, permethrin-allethrin, and permethrin-tetramethylfluthrin accounted for 41.17%. Conclusion Aedes albopictus in Fengxian district has developed resistance to deltamethrin and beta-cypermethrin insecticides. A reasonable rotation or mixed use of insecticides should be adopted to effectively alleviate and reduce the development of insecticide resistance.

Objective To investigate the resistance to common insecticides in Aedes albopictus, Musca domestica, and Blattella germanica in Hongkou district, Shanghai, China, and to provide a scientific basis for rational selection and use of insecticides. Methods The larval dipping method recommended by WHO was used to test the resistance of Ae. albopictus larvae to insecticides by measuring median lethal concentrations. Micro-topical application was used to test the resistance of M. domestica to insecticides by determining median lethal doses. The residual film method was applied to test the resistance of B. germanica to insecticides by recording median knockdown time. Results In 2017 and 2019, Ae. albopictus larvae in Hongkou district of Shanghai showed resistance ratios of 0.44 (low resistance) and 4.94 (moderate resistance) to temephos, respectively; in 2017, the resistance ratio to beta-cypermethrin was 16.89 (moderate resistance); deltamethrin resistance ratios were 34.25 (moderate resistance); the resistance ratio to propoxur was 1.59 (sensitive); in 2019, the larvae exhibited a moderate resistance level of 13.40 to permethrin. In 2016 and 2018, M. domestica were at high resistance levels of 29.07 and 39.53 to beta-cypermethrin, respectively; in 2016, the ratios for deltamethrin and dichlorvos were 112.86 (high resistance) and 4.37 (low resistance), respectively; in 2018, the ratios for pirimiphos-methyl and permethrin were 4.03 (low resistance) and 13.08 (moderate resistance), respectively. In 2015 and 2018, the resistance ratios of B. germanica to beta-cypermethrin were 3.05 (low resistance) and 1.60 (sensitive), respectively; the ratios for deltamethrin were 4.31 (low resistance) and 6.13 (low resistance), respectively; the ratios for acephate were 0.93 (low resistance) and 1.10 (low resistance), respectively; in 2015, B. germanica showed a low resistance ratio of 2.69 to propoxur. Conclusion Aedes albopictus, M. domestica, and B. germanica in Hongkou district have varying degrees of resistance to commonly used insecticides. It is necessary to strengthen insecticide resistance surveillance and formulate management strategies for scientific and rational use of insecticides.

Objective To investigate the current status and development in the resistance of Aedes albopictus and Musca domestica to common insecticides in Shanghai, China, and to provide a theoretical basis for the scientific and rational use of chemical insecticides. Methods The larval dipping method recommended by WHO was used to test resistance for the late third-instar or early fourth-instar larvae of Ae. albopictus. Topical application was used to determine resistance for female M. domestica at 3-5 days post eclosion. Results At all surveillance points, the resistance of Ae. albopictus and M. domestica to pyrethroids was significantly higher than that to carbamates and organophosphates. The percentages of areas where Ae. albopictus was sensitive to temephos and deltamethrin increased from 33.33% to 44.44% and 6.67% to 12.50%, respectively; resistance to beta-cypermethrin and propoxur showed a growing trend, and the percentages of areas with high beta-cypermethrin resistance increased from 6.67% to 20.00% and propoxur-resistant areas reached 100%. For M. domestica, dichlorvos resistance showed a downward trend, and the proportions of sensitive areas grew from 16.67% to 50.00%; the percentages of areas with resistance to beta-cypermethrin and deltamethrin increased, and the latter even rose from 84.62% to 100%, increasing by 18.20% year on year; resistance to pirimiphos-methyl generally exhibited an upward trend, and the proportion of high resistance ascended to 33.33%, with an increase of 33.33% year on year. Conclusion Aedes albopictus and M. domestica in Shanghai have developed varying degrees of resistance to common insecticides such as organophosphates, pyrethroids, and carbamates. It is recommended that insecticides with high resistance should be discontinued for 1-2 years, agents with moderate resistance should be used appropriately, and those with low resistance can be used alternately, in order to delay the development of resistance in Shanghai, China.

Objective To investigate the genotypes and distribution characteristics of the ace gene of the dengue vector Aedes albopictus (field population) in different regions of China, and to preliminarily explore their resistance mechanism to organophosphorus and carbamate insecticides. Methods A total of 422 larvae, pupae, or adults of Ae. albopictus were collected at 14 sampling sites (14 geographical populations) in Haikou of Hainan province, Guangzhou of Guangdong province, Jinghong of Yunnan province, and Xingyi of Guizhou province from June to September 2018, and they were identified by morphology or molecular biology, soaked in anhydrous ethanol, and stored at -20℃. DNA was extracted from individual mosquito, and the partial fragment of the ace gene was amplified by PCR, sequenced, and analyzed for mutation at G119. Results There were only a few base mutations but no amino acid mutations at G119 of the ace gene. Two alleles were detected, namely wild-type GGA/G (832/98.58%) and mutant-type GGG/G (12/1.42%), and one genotype was detected, namely wild-type homozygote G/G (422/100%). Conclusion Only a few individuals of Ae. albopictus showed a base mutation at G119 of the ace gene, but the base substitution did not cause the corresponding amino acid mutation. Therefore, the resistance mechanism of Ae. albopictus to organophosphorus and carbamate insecticides needs to be further explored.

Objective To investigate the levels and distribution of resistance of Aedes albopictus to several commonly used insecticides in different areas of China, and to provide guidance for the resistance control and use of insecticides in China. Methods Excel 2016 software was used to collect and organize the bioassay data on the resistance of larval and adult Ae. albopictus to pyrethroids, carbamates, and organophosphorus insecticides in China from 2017 to 2018, and the level of resistance was statistically analyzed. ArcGIS 10.3 software was used to draw the resistance map of different insecticides. Results By collecting monitoring data in 2017 and 2018 and reviewing the relevant literature, we obtained the bioassay data on the resistance of Ae. albopictus to commonly used insecticides in 15 provinces, and then analyzed the data on the resistance to pyrethroids (deltamethrin, permethrin, and beta-cypermethrin), carbamates (propoxur), and organophosphates (malathion, temephos, and DDVP). Aedes albopictus larvae developed medium and high resistance to deltamethrin, permethrin, and beta-cypermethrin at 34 (85.00%), 18 (75.00%), and 33 (78.57%) monitoring sites, respectively, and the adult mosquitoes developed resistance or high resistance to deltamethrin, permethrin, and beta-cypermethrin at 34 (61.82%), 8 (34.78%), and 11 (34.38%) monitoring sites, respectively. Aedes albopictus larvae developed medium and high resistance to propoxur and temephos at 5 (27.78%) and 14 (36.84%) monitoring sites, respectively, and the adult mosquitoes developed resistance to propoxur and temephos at 7 (20.59%) and 4 (14.29%) monitoring sites, respectively. Conclusion Both adult and larval Ae. albopictus in most areas of China, especially coastal areas such as Guangdong and Fujian provinces, has developed high levels of resistance to pyrethroid insecticides; the resistance levels of carbamates and organophosphorus insecticides are relatively low. Local use of insecticides should be guided based on local conditions and the monitoring results; high-resistance insecticides should be stopped for a period of time, and the insecticides to which Ae. albopictus has developed medium and low resistance or suspected resistance should be used alternately or in combination.