20 October 2023, Volume 34 Issue 5
    

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    Experimental Study
  • Role of miR-276-3p in regulation of chitin metabolism in Aedes albopictus larvae
    FU Jing-wen, LIU Wen-juan, ZHANG Zhong, ZHANG Rui-ling
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 589-595. https://doi.org/10.11853/j.issn.1003.8280.2023.05.001
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    Objective To investigate the role of miR-276-3p in the chitin metabolism of Aedes albopictus larvae, so as to provide a new target for the control of Ae. albopictus using chitin metabolism-related miRNAs.Methods miR-276-3p-specific mimic agomir and inhibitor antagomir chitosan nanoparticles were synthesized to overexpress and suppress the expression of miR-276-3p in Ae. albopictus larvae through feeding, respectively. The relative expression of miR-276-3p in larvae was measured by reverse transcription quantitative real-time PCR. The chitin levels of larvae and pupae were determined using biochemical assay. The survival rate and pupation rate of larvae and the eclosion rate of pupae were calculated. Two-way ANOVA was used for mirR-276-3p expression differences analysis, T-test was used for chitin content comparison between different groups, and the log-rank test and Mantel-Cox test were used for survival rate difference analysis.Results miR-276-3p agomir chitosan nanoparticles effectively overexpressed miR-276-3p in Ae. albopictus larvae, the expression on the 1st and 3rd days increased by 73.96% (F=932.401, P<0.001) and 16.95% (F=114.551, P=0.047) respectively, while miR-276-3p antagomir chitosan nanoparticles significantly suppressed the expression of miR-276-3p in Ae. albopictus larvae, the expression on the 1st and 5th days decreased by 13.42% (F=293.632, P<0.001) and 1.49% (F=69.542, P=0.014) respectively. The overexpression of miR-276-3p increased the chitin content by 25.34% (t=85.838, P=0.019). The survival rate decreased significantly, and the difference between the experimental group and the control group on the 8th day was statistically significant (χ2=77.490, P=0.020), and the pupation rate was 70.00%, which was 90.00% and lower than that of the control group. The suppression of miR-276-3p reduced chitin levels in the larvae by 40.06% (t=71.811, P=0.028) and pupae by 46.82% (t=92.147, P=0.011) of Ae. albopictus.Conclusions miR-276-3p has significant effects on the chitin content,survival rate,and pupation rate of Ae. albopictus larvae. This study provides basic data for mosquito control by using miRNAs to regulate chitin metabolism in Ae. albopictus larvae.
  • Effect of botanical attractants combined with spraying insecticides in improving the effectiveness of cockroach prevention and control
    HAO Hui-ling, LYU Hong-yan, SUN Bin
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 596-599. https://doi.org/10.11853/j.issn.1003.8280.2023.05.002
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    Objective To screen for the effective attractants for cockroaches, and to investigate the feasibility of attractants combined with spraying insecticides in improving the effectiveness of cockroach prevention and control.Methods The small container trapping method was used to determine the attractability of citral, terpinen-4-ol, and HT-1 phenol to Blattella germanica; the topical application method was used to determine the synergistic activity of citral, terpinen-4-ol, and HT-1 phenol on ethofenprox against B. germanica; a simulation laboratory was used to investigate the effect of the attractants combined with ethofenprox in attracting and killing B. germanica. The Duncan test is used to analyze the differences in the attractability of different compounds to German cockroaches.Results Citral, terpinen-4-ol, and HT-1 phenol had marked attractability to B. germanica, with a relative attraction rate increased by 16.73%, 12.33%, and 31.01%, respectively, at a concentration of 1.0%, while repellency was observed at a concentration of 5.0%. The synergistic rate of 2.5% citral, terpinen-4-ol, and HT-1 phenol to ethofenprox against B. germanica were 73.81%, 47.12%, and 40.90%, respectively. In the simulation laboratory, citral, terpinen-4-ol, and HT-1 phenol combined with ethofenprox increased the contact between the tested cockroaches and insecticide-impregnated paper, with a relative attraction rate increased by 22.22%, 7.26%, and 30.29%, respectively, and such combination also improved killing effect, with a synergistic rate of 72.51%, 67.01%, and 39.93%, respectively.Conclusion Botanical attractants act as a synergist by inducing pests to contact with insecticides and can reduce the use of chemical insecticides while improving killing effect, which provides a new technical approach for the prevention and control of pests.
  • Resistance to three pyrethroid insecticides and knockdown resistance gene mutations in Aedes albopictus in Guiyang,Guizhou Province,China
    ZHANG Yan, WANG Dan, ZHOU Jing-zhu, SHI Wei-fang, LUO Xiao-long, KONG Xue-xue, YU Hao, GUAN Yu-wei, HU Yong, LIANG Wen-qin
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 600-606. https://doi.org/10.11853/j.issn.1003.8280.2023.05.003
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    Objective To evaluate the level of resistance of Aedes albopictus to pyrethroid insecticides in Guiyang,China,and identify mutations in the knockdown resistance gene, so as to provide a scientific basis for the control of Ae. albopictus in the region.Methods From July to August 2022,the larvae of Ae. albopictus were captured at different locations of Guiyang and then reared to F1-F2 generations in the laboratory. The resistance to pyrethroid insecticides was determined by using the dipping method for larvae and the World Health Organization tube method for adult mosquitoes. The genomic DNA of individual adult Ae. albopictus mosquito was extracted for PCR amplification and sequencing to detect knockdown resistance gene mutations. The Chi-square test was used to analyze the frequency differences of mutant genes between groups.Results The median lethal concentrations of deltamethrin, permethrin, and beta-cypermethrin against Ae. albopictus larvae in Guiyang were 0.559, 0.021, and 0.012 mg/L, respectively;and the resistance ratios were 433.33, 46.67, and 16.44, respectively. The mortality rates of adult Ae. albopictus mosquitoes exposed to 0.03% deltamethrin, 0.4% permethrin, and 0.08% beta-cypermethrin were all <80%. No mutations were detected at the 1016, 1532, and 1534 loci in the sensitive population of Ae. albopictus. Knockdown resistance gene mutations were found at all the three loci in the natural population of Ae. albopictus. There were two alleles at 1016 locus, which were wild-type GTA (V) (76.35%) and mutant GGA (G) (23.65%), with no statistically significant differences in frequency of mutant genes between the sensitive and resistant phenotypes (χ2=1.810, P=0.178); There were three genotypes at 1016 locus: wild-type homozygous V/V (58.78%), wild/mutant heterozygous V/G (35.14%),and mutant homozygous G/G (6.08%). There were two alleles at 1532 locus, which were wild-type ATC (I) (99.83%) and mutant ACC (T) (0.17%),with two genotypes of wild-type homozygous I/I (99.66%) and wild/mutant heterozygous I/T (0.34%). There were two alleles at 1534 locus, namely wild-type TTC (F) (48.48%) and mutant TCC (S) (51.52%),with no statistically significant difference in frequency of mutant genes between the sensitive and resistant phenotypes (χ2=0.603, P=0.437); There were three genotypes at 1534 locus: wild-type homozygous F/F (8.11%), wild/mutant heterozygous F/S (80.74%),and mutant heterozygous S/S (11.15%).Conclusions Larval and adult Ae. albopictus mosquitoes in Guiyang have developed medium-to-high resistance to the three pyrethroid insecticides and mutations in the knockdown resistance gene,but with no significant association between the mutations and the resistant phenotypes. The level of resistance in the region should be continuously monitored to guide the scientific and rational use of insecticides to effectively control mosquitoes and delay the evolution of insecticide resistance.
  • Whole-genome sequence analysis of three strains of Hantavirus in Zhoushan Islands, Zhejiang Province, China
    SHU Ji-wei, CHEN Xu-hui, TAN Qi-long, HUANG Zhe, YE Ling, WANG Zhi-ping, HUANG Mao-wen, LI Shi-bo, CHEN Qian, ZHANG Tong-jie
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 607-611. https://doi.org/10.11853/j.issn.1003.8280.2023.05.004
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    Objective To analyze the whole-genome sequences of Hantavirus in rodent lung samples collected from Zhoushan Islands in Zhejiang province, China in 2021.Methods Nested PCR was used to amplify the Hantavirus nucleic acid in Hantavirus positive rodent lung samples. The sequence was assembled by SeqMan 7.1.0.44 in DNAStar, and the sequence alignment and phylogenetic analysis were performed by MEGA 7.0.Results The whole-genome sequences of three Hantavirus strains were successfully determined, all of which were identified as Seoul (SEOV) S3 subtype, with high homology with strains from Rui'an in Zhejiang, Liaoning, and Shandong. They showed high homology in nucleotide and amino acid sequences and consistent immune epitopes of 2 glycoproteins and 4 nucleoproteins with the vaccine strain Z37.Conclusion This study first reported the whole-genome sequences of Hantavirus isolated from Zhoushan Islands in Zhejiang Province, which provides a reference for the study of the epidemic characteristics of hemorrhagic fever with renal syndrome and the virus evolution patterns in this area.
    • Vector Surveillance
  • Resistance of Blattella germanica to commonly used insecticides in Wuhu, Anhui Province, China, 2022
    HOU Yin-xu, WANG Fei, AN Zhou, TONG Fei, RUI Zhen-yu, TAI De-yun, REN Dong-sheng, MENG Feng-xia, WU Lei, XU Qing-hua
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 612-616. https://doi.org/10.11853/j.issn.1003.8280.2023.05.005
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    Objective To investigate the resistance levels of Blattella germanica in Wuhu, Anhui Province, China, so as to provide a scientific basis for rational insecticide use.Methods From March to June 2022, test B. germanica cockroaches were collected from restaurants, bakeries, hotels, supermarkets, and farmers' markets in Yijiang, Jinghu, Sanshan, and Jiujiang districts of Wuhu. The resistance of B. germanica to 12 commonly used insecticides was determined using the residual film method. SPSS 22.0 was used for data processing and analysis.Results The 24 h mortality rates of B. germanica treated with permethrin, tetramethrin, cypermethrin, deltamethrin, alpha-cypermethrin, beta-cypermethrin, lambda-cyhalothrin, propoxur, azamethiphos, acephate, dichlorvos, and chlorpyrifos were 91.20%, 18.40%, 91.33%, 89.47%, 77.85%, 92.62%, 99.19%, 100%, 96.85%, 100%, 76.06%, and 99.00%, respectively. The median knockdown time (KT50) was 32.63, 900.61, 28.17, 30.47, 26.60, 11.06, 16.54, 17.93, 14.13, 59.66, 27.57, and 38.21 min, respectively. According to the resistance criteria by mortality, B. germanica in Wuhu was sensitive to lambda-cyhalothrin, propoxur, azamethiphos, acephate, and chlorpyrifos; potentially resistant to permethrin, cypermethrin, deltamethrin, and beta-cypermethrin; and resistant to tetramethrin, alpha-cypermethrin, and dichlorvos. Based on the knockdown resistance criteria, B. germanica in Wuhu was sensitive to azamethiphos; lowly resistant to beta-cypermethrin, lambda-cyhalothrin, propoxur, acephate, and chlorpyrifos, with the resistance ratios being 2.58, 3.21, 1.39, 2.01, and 1.41, respectively; moderately resistant to permethrin, cypermethrin, deltamethrin, alpha-cypermethrin, and dichlorvos, with the resistance ratios being 6.54, 6.39, 7.79, 5.58, and 7.14, respectively; and extremely high resistant to tetramethrin, with the resistance ratio being 259.54. KT50 or 24 h mortality had no significant correlation with insecticide consumption (rKT50-inseciticide consumption=0.045, r24 h mortality-insecticide consumption=0.141, all P>0.05).Conclusions B. germanica in Wuhu has developed medium or high resistance to a variety of insecticides. In cockroach control, the use of insecticides should be regulated according to the results of resistance monitoring to delay the development of resistance.
  • An analysis of surveillance results of intermediate hosts of Paragonimus in Xiuning County, Anhui Province, China, 2019-2021
    LIU Dao-hua, JIN Yu, LI Qi-yang, YANG Rong-sheng, WANG Tian-ping, CAO Zhi-guo
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 617-621. https://doi.org/10.11853/j.issn.1003.8280.2023.05.006
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    Objective To investigate the status of Paragonimus infection in intermediate hosts in Xiuning County, Anhui Province, China, so as to provide scientific evidence for formulating paragonimiasis control strategies.Methods From 2019 to 2021, small freshwater snails and crabs were captured in nine administrative villages in three towns along Xiuning river, Heng river, and Shuaishui river in Xiuning County. The freshwater snails and crabs were morphologically identified, and then were examined for Paragonimus cercariae and metacercariae, respectively. The metacercaria infection index of crabs was calculated to determine the levels of paragonimiasis epidemic foci. EpiData 3.1 and SPSS 23.0 were used for statistical analysis.Results Two kinds of small freshwater snails were collected, which were morphologically identified as Assiminea sp. and Semisulcospira libertina. Among a total of 3 826 Assiminea snails, no Paragonimus cercariae were detected. Among a total of 10 440 S. libertina snails, the overall infection rate was 0.89% (93/10 440); the infection rate was highest in Ru village (23/1 021, 2.25%) and lowest in Yanjiao village (4/743, 0.54%), with a statistical difference in the infection rate between the surveyed points (χ2=24.784, P=0.002). The crabs were identified as Sinopotamon yangtsekiense, and the overall infection rate was 21.41% (106/495). The infection rate of the crabs was highest in Ru village (25/76, 32.89%) and lowest in Yanjiao village (3/51, 5.88%), with a statistical difference between the surveyed points (χ2=16.225, P=0.039). The metacercaria infection index results of Ru village, Nantang village, and Jiangtan village were 0.12, 0.02, and 0.03, respectively, all being level-Ⅲ epidemic foci of paragonimiasis.Conclusions The intermediate hosts of Paragonimus in Xiuning County had a relatively high infection rate. Public health education on paragonimiasis should be strengthened to prevent the epidemic of paragonimiasis in this area.
  • Ecological monitoring and virus carrying status of mosquitoes in Taizhou, Zhejiang Province, China, 2017-2022
    ZHAO Yi-shuang, JIAN Yue, YOU Xiao-jie, WANG Min-ya, CHEN Cai-rong
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 622-627. https://doi.org/10.11853/j.issn.1003.8280.2023.05.007
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    Objective To investigate the species composition, density, seasonal variation, and virus-carrying status of mosquitoes in Taizhou, Zhejiang Province, China, since the implementation of the new vector surveillance program in 2017-2022, so as to provide a scientific basis for the control of mosquito vectors and the early warning of mosquito-borne diseases.Methods Surveillance sites were set up in 9 counties (cities and districts) of Taizhou, and the light trapping method and Breteau index (BI) method were used to perform ecological surveillance of adult and larval mosquitoes from April to November every year. From June to August in 2022, adult mosquitoes were collected in Luqiao District, and quantitative real-time PCR was used to detect six viruses including Dengue virus, Japanese encephalitis virus, West Nile virus, Chikungunya virus, Yellow fever virus, and Sindbisvirus. SPSS 20.0 software was used to perform a statistical analysis of surveillance data.Results In 2017-2022, a total of 4 800 mosquito trap lamp·nights were deployed in Taizhou, and 109 160 female mosquitoes were captured in total, with a mean mosquito density of 22.74 mosquitoes/lamp·night, among which there were 76 799 Culex tritaeniorhynchus mosquitoes, accounting for 70.35%, followed by 20 724 Cx. pipiens pallens/quinquefasciatus mosquitoes, accounting for 18.98%. June to September was the peak period of mosquito activity. In different habitats, livestock shed (livestock farm) had the highest mosquito density of 92.91 mosquitoes/lamp·night. Cx. tritaeniorhynchus was the dominant species in livestock shed (livestock farm), accounting for 83.08%, and Cx. pipiens pallens/quinquefasciatus was the dominant species in residential area and other habitats, with a composition ratio of >60%. There was a significant difference in the composition ratio of mosquito species between different habitats (χ2=60 286.496, P<0.001). A total of 94 523 households were surveyed for mosquito larvae surveillance, with a mean BI of 16.94. All the monthly average BI from April to November were greater than 5. Positive stagnant water was mainly observed in idle containers (bowls, bottles, jars, and tanks), accounting for 54.88%, and the highest breeding rate of Aedes (37.37%) was observed in tires/waste tires. A total of 1 050 female Cx. pipiens pallens/quinquefasciatus mosquitoes and 1 140 female Ae. albopictus mosquitoes were detected for above 6 viruses, and all mosquitoes were negative for the six viruses.Conclusions Cx. pipiens pallens/quinquefasciatus is the dominant mosquito species in the residential area in Taizhou, and there is a relatively high density of mosquitoes in livestock shed (livestock farm) where the dominant mosquito species is Cx. tritaeniorhynchus. There is a risk of dengue fever transmission from April to November. It is necessary to strengthen comprehensive mosquito control measures focusing on environmental management, so as to prevent the transmission and epidemic of imported or indigenous mosquito-borne diseases..
  • Surveillance results of rodent-borne pathogens in Chongqing, China, 2021-2022
    XIAO Han-sen, HE Ya-ming, TU Tao-tian, ZHANG Ying, WANG Zheng, JI Heng-qing
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 628-632. https://doi.org/10.11853/j.issn.1003.8280.2023.05.008
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    Objective To monitor five common pathogens carried by small mammals in key areas of Chongqing, China, so as to provide a scientific basis for the prevention and control of local rodent-borne diseases.Methods From 2021 to 2022, small mammals were collected using cage traps at night at three surveillance sites in the central urban area, Wanzhou District, and Fuling District of Chongqing. The liver, spleen, lung, and kidney tissues were collected to extract nucleic acids for detection of Leptospira interrogans, Rickettsia mooseri, and Bartonella by quantitative real-time PCR (qPCR) as well as Hantavirus and Dabie bandavirus by reverse transcription qPCR. Excel 2010 was used to sort and arrange the data. The SPSS 22.0 software performed statistical analysis on the experimental data. The species composition ratio and pathogen infection rate of rodents were compared by the Chi-squared test.Results A total of 1 188 small mammals were collected, among which Rattus norvegicus accounted for 33.50%, R. tanezumi accounted for 26.77%, Anourosorex squamipes accounted for 26.01%, and Mus musculus accounted for 9.85%, in addition to Leopoldamys edwardsi, R. nitidus, N. confucianus, Apodemus agrarius, and Crocidura attenuata, with a total of nine species. There was a significant difference in the species composition of small mammals between different surveillance sites (χ2=714.786, P<0.001). Four samples were positive for Seoul Hantavirus, 24 for L. interrogans, and 8 for Bartonella; the remaining samples were negative. A total of 33 small mammals were found positive, including 2 R. tanezumi and 1 R. norvegicus carrying both L. interrogns and Seoul Hantavirus. The overall infection rate was 2.78% for all pathogens, 0.34% for Hantavirus, 2.02% for L. interrogans, and 0.67% for Bartonella. There was a significant difference in the infection rates of the three pathogens (χ2=18.857, P<0.001).Conclusions L. interrogans, Bartonella, and Hantavirus were detected in small mammals in Chongqing. These pathogens were most frequently found in R. norvegicus, R tanezumi, and A. squamipes, which were mainly distributed in the key industries of urban Chongqing and the rural residential areas of Wanzhou District, and the authorities of these places should pay more attention to the spread and control of rodent-borne diseases.
  • An analysis of plague monitoring results in Wuhai City, Inner Mongolia Autonomous Region, China, 2013-2022
    LIU Fu-sheng, XUE Pei-miao, HUANG Xi-ping, WANG Bao-zhong, ZHENG Mei
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 633-636. https://doi.org/10.11853/j.issn.1003.8280.2023.05.009
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    Objective To investigate the changes in the density of Meriones unguiculatus and the composition of rodents in plague foci of Wuhai City, Inner Mongolia Autonomous Region, China, in 2013-2022, as well as their carrying status of Yersinia pestis, so as to provide a scientific basis for plague surveillance, prevention, and control.Methods The hectare day trapping method was used for the density monitoring and sampling of M. unguiculatus, and the 5 m trap line method was used to monitor the density of nocturnal rodents. The daily rodent trapping method and the active foot survey method were used for expanded search, and Y. pestis was detected in laboratory by microscope smear examination, bacterial culture, bacteriophage test, indirect hemagglutination assay, reverse hemagglutination test, and PCR nucleic acid detection. The descriptive epidemiological methods were used for statistical analysis.Results In 2013-2022, the average density of M. unguiculatus was 0.65 rodents/hm2 in plague foci in Wuhai by the hectare day trapping method. A total of 839 rodents belonging to 9 species were captured by three methods, among which M. unguiculatus was the dominant species, accounting for 57.21%. Two strains of Y. pestis were detected in 2020, and two samples tested positive for Y. pestis by PCR nucleic acid detection, while no positive results were observed in the other years.Conclusions There will be a weak epidemic period in the plague foci of M. unguiculatus in Hainan District of Wuhai City. However, it is still necessary to strengthen the monitoring and early warning of rodents and plague, and enhance the health education on plague and behavioral intervention for employees of newly built enterprises and farmers and herdsmen in the epidemic foci, so as to timely identify the epidemic of plague between animals and prevent the occurrence of human plague.
  • Ecological surveillance result of flies and resistance of Musca domestica to commonly used insecticides in Nanjing, China, 2022
    SONG Bing-dong, ZHANG Yan, MIN Yue, CHEN Xue-min, CHEN Hang, SUN Nan, LU Mo-yuan, WANG Chong, ZHANG Shou-gang
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 637-641. https://doi.org/10.11853/j.issn.1003.8280.2023.05.010
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    Objective To investigate the population distribution and density of flies and the insecticide resistance levels of Musca domestica in Nanjing, China, so as to provide a basis for formulating scientific, rational, and effective prevention and control measures.Methods From March to November, 2022, the cage trapping method was used for fly ecological surveillance, and the topical application method was used to determine the insecticide resistance of M. domestica. The density and composition ratio of flies were calculated using Excel 2010. Using SPSS 23.0 software, a Probit regression analysis was performed to calculate the median lethal dose (LD50), regression equation, and resistance ratio.Results M. domestica was the dominant species of flies in Nanjing in 2022, accounting for 21.85%. The average annual fly density was 2.94 flies/cage in Nanjing. Among the surveillance points, Liuhe District had the highest fly density of 8.85 flies/cage. Among different habitats, farmers' markets had the highest fly density of 3.44 flies/cage. Among different fly species, M. domestica showed the highest density in four habitats, which was 0.64 flies/cage. The fly density showed a unimodal pattern, which reached a peak in July at 5.95 flies/cage. For M. domestica, the LD50 values of deltamethrin, beta-cypermethrin, dichlorvos, phoxim, and propoxur were 0.172 7, 0.288 6, 0.145 2, 0.114 3, and 0.916 7 μg/individual, respectively; the resistance ratios were 863.50, 41.23, 242.00, 36.87, and 3.08, respectively.Conclusions M. domestica was the dominant fly species in Nanjing, with varying degrees of resistance to deltamethrin, beta-cypermethrin, dichlorvos, and phoxim. The use of these four insecticides should be stopped or reduced, and some sensitive and low-resistance insecticides should be selected for rotation gradually.
  • An analysis of surveillance results of small mammals and body surface fleas in the Chongqing section of the Three Gorges Reservoir Region, China, 2019-2021
    WANG Ling, HE Ya-ming, JI Heng-qing, LI Zhi-feng, ZHAO Ting, HUANG Wei, XIAO Han-sen
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 642-647. https://doi.org/10.11853/j.issn.1003.8280.2023.05.011
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    Objective To analyze the surveillance results of small mammals and their body surface flea vectors in the Chongqing section of the Three Gorges Reservoir Region, China, ao as to provide basic data and scientific guidance for the prevention and control of rodent-borne diseases.Methods The surveillance data of small mammals and their body surface flea vectors in the Chongqing section of the Three Gorges Reservoir Region from 2019 to 2021 were collected to analyze the changes in the species composition, density, flea infestation rate, and flea index of small mammals. The Chi-squared test was performed for analysis of data using SPSS 25.0.Results A total of 2 860 small mammals of 10 species were found in the Chongqing section of the Three Gorges Reservoir Region, with a mean density of small mammals of 1.67%. In residential areas, the mean small mammal density was 2.74%; the density showed a decreasing trend over the years (χ2=22.493, P<0.001); and the dominant species were Rattus tanezumi, R. norvegicus, and Mus musculus. In cropland, the mean density of small mammals was 0.60%; the density of small mammals fluctuated at relatively low levels, with a statistical difference between the years (χ2=41.953, P<0.001); and the dominant species were R. tanezumi, Anourosorex squamipes, and Leopoldamys edwardsi. There was a statistical difference in the composition ratio of small mammals between residential areas and cropland areas (χ2=1 003.754, P<0.001). The flea infestation rate of the small mammals was 18.67%, and the total flea index was 0.70. The dominant flea species was Leptopsylla segnis. Serum antibody against plague was not detected.Conclusions The species and density of small mammals in the Chongqing section of the Three Gorges Reservoir Region during 2019 to 2021 have changed significantly as compared with the completion of the Three Gorges Reservoir. R. tanezumi is the dominant rodent species, and its indoor density is much higher than the national plague control standard limit. The flea species include L. segnis and Xenopsylla cheopis. Great attention should be paid to strengthening plague monitoring and timely rodent and flea control.
  • An analysis of cockroach surveillance results in catering industry in Shandong Province, China, 2010-2020
    LIANG Qian, LIU Wen-jie, MA Wei, SUN Qin-tong, LIU Yan, CAO Xin-yue, WANG Xue-jun
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 648-653. https://doi.org/10.11853/j.issn.1003.8280.2023.05.012
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    Objective To investigate the species composition and seasonal fluctuation of cockroaches in catering industry in Shandong Province, China, so as to provide a basis for scientific control of cockroaches.Methods The cockroaches were captured by using sticky traps at the surveillance sites of the catering industry of Shandong Province in each month of 2010-2016 and odd-numbered months of 2017-2020. The surveillance data were compiled using Excel 2010 software. R 4.1.1 was used to conduct statistical analyses of the species composition, sticky trapping rate, and density of cockroaches. The χ2 test was used to analyze the population composition and the sticky trapping rate of cockroaches in different years and different regions. The temporal trend of the sticky trapping rate was determined using the Cochran-Armitage trend test.Results A total of 15 521 cockroaches were captured at the catering industry surveillance sites in Shandong Province during 2010 to 2020, including 15 481 Blattella germanica cockroaches (composition ratio, 99.74%), 6 Periplaneta americana cockroaches (composition ratio, 0.04%), and 34 cockroaches of other species (composition ratio, 0.22%). The average sticky trapping rate was 13.07%, and the average density was 0.83 cockroaches/trap. The average density of cockroaches in the catering industry of Jining was the highest, which was 2.04 cockroaches/trap. The sticky trapping rate in the catering industry of Dongying was the highest, with an average sticky trapping rate of 24.50%. The overall sticky trapping rate showed a decreasing trend in the catering industry of Shandong Province (Z=-15.200, P<0.001). The density and the sticky trapping rate of cockroaches peaked in summer and autumn, mostly in September.Conclusions B. germanica was the dominant species in the catering industry of Shandong Province. The overall sticky trapping rate showed a decreasing trend, but the average sticky trapping rate was high. Sustainable control and comprehensive management measures should be taken according to the habitat characteristics of catering industry to effectively control the density of cockroaches.
    • Early Warning and Forecast
  • Fine-scale dengue transmission risk prediction based on multi-source geographic data in Guangzhou,China
    ZHANG Meng-zhen, REN Zhou-peng, FAN Jun-fu, XIAO Jian-peng, ZHANG Ying-tao
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 654-663. https://doi.org/10.11853/j.issn.1003.8280.2023.05.013
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    Objective This study predicted the risk of dengue fever transmission on a fine scale, aiming to meet the practical needs of meticulous prevention and control and to provide a reference for relevant departments to formulate more precise response plans against dengue fever.Methods A Random Forest model was constructed to predict the risk of dengue fever transmission at a fine resolution of 1 km×1 km based on the data on dengue fever cases as well as natural and socio-economic factors including precipitation, land surface temperature, population density, road density, the normalized difference vegetation index, hospital accessibility, bus stop density,and the Shannon evenness index of land use in Guangzhou, China from 2017 to 2019.Results Compared with the models based on undersampling or combined sampling, the oversampling-based prediction model had better precision, with the area under the curve (AUC) being 0.999, accuracy being 0.978, precision being 0.999, recall being 0.959, and F1 value being 0.979. The analysis of the importance of single factors in dengue fever prediction revealed that the importance of population density was much higher than those of the other variables, with an average increase in mean squared error of 63.76; hospital accessibility was the second important feature;the average land surface temperature had the lowest importance among the selected variables, with an average increase in mean squared error of 35.42. The distribution of dengue fever transmission risk was consistent with the distribution of populated areas in Guangzhou. The high-risk areas accounted for 6.18% of the total area, and the at-risk populations in the high-risk areas accounted for 39.13% of the total population. More than 80.00% of the population in Yuexiu, Liwan, Haizhu, and Tianhe districts were in the high-risk areas.Conclusions The risk of dengue transmission in Guangzhou was mainly distributed in the central urban areas of Guangzhou, with Yuexiu, Liwan, and Haizhu districts as the center, extending northward to central Baiyun District, southward to the junction of Panyu and Nansha districts, and eastward to eastern Huangpu District. The predicted risk areas were highly consistent with case distributions, indicating that the method proposed in this study can more accurately depict the geographical distribution of dengue transmission risk.
  • Species and their identification of ectoparasitic fleas on small mammal in Haidong City,Qinghai Province,China
    WANG Jin-suo, ZHAO Yan-mei, WEI You-wen, ZHOU Kui-zhang, LI Ji-de, MA Ying
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 664-670. https://doi.org/10.11853/j.issn.1003.8280.2023.05.014
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    Objective To investigate the species composition,host selection,and distribution of ectoparasitic fleas on small mammals in Haidong,Qinghai Province,China based on plague foci surveillance data,and to identify the species of some common fleas and difficult-to-identify fleas by molecular method to find a way that can improve the accuracy of flea species identification and classification.Methods Flea species was identified by traditional morphological classification and molecular identification based on of the cytochrome c oxidase subunit Ⅰ (COⅠ) gene.Results A total of 61 species (subspecies) of ectoparasitic fleas were found and recorded in Haidong,belonging to 28 genera,5 families,and 4 superfamilies. The partial fragments (about 658 bp) of the COⅠ gene were sequenced for 99 fleas of 20 species under 13 genera and 4 families. The intraspecific and interspecific genetic distances were 0.2%-2.9% and 3.3%-22.9%, respectively. The interspecific distance was significantly greater than the intraspecific distance.Conclusion The flea species formed single lineages with support values greater than 99% in the phylogenetic tree,indicating that the combination of COⅠgene characterization and traditional morphological classification can accurately identify flea species in Haidong.
  • MaxEnt model-based analysis of distribution of suitable habitats of Ornithodoros ticks in Xinjiang Uygur Autonomous Region,China
    LIU Ming-ming, LIU Dan-dan, LU Xing, WANG Shui-yi, LIU Yu-tong, JIANG Bing-bing, ZHU Hui-ru, DU Shao-lei, Bayinchahan, ZHANG Wei
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 671-678. https://doi.org/10.11853/j.issn.1003.8280.2023.05.015
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    Objective To study the distribution of suitable habitats of Ornithodoros ticks in Xinjiang Uygur Autonomous Region (Xinjiang),China under current and future climate scenarios.Methods The Ornithodoros distribution data in Xinjiang in 2002-2022 were obtained through field sampling and literature search. The obtained distribution data were sorted and plotted by ArcGIS 10.6 software. The climate data in Xinjiang in the past 30 years and future 80 years were obtained through the WorldClim 2.1 database. The main environmental variables were selected using the maximum entropy (MaxEnt) jackknife test and Spearman correlation analysis. The selected Ornithodoros distribution data and environmental variables were used to construct a MaxEnt model for predicting and projecting the current and future potential suitable habitats of Ornithodoros in Xinjiang. The predictive performance of the model was assessed using the area under the receiver operating characteristic curve (AUC). The relative effects of different environmental variables on the potential distribution of Ornithodoros were assessed using the MaxEnt jackknife test. The specific effects of environmental variables on the potential distribution of Ornithodoros were analyzed using the response curves derived from the MaxEnt model. The results were visualized and reclassified using ArcGIS 10.6 software to analyze the potential distribution of Ornithodoros and the suitable habitat area in Xinjiang under current and future (ssp245) climate scenarios.Results A total of 65 distribution data of Ornithodoros and six environmental variables were selected from 82 pieces of distribution data and 20 environmental variables through query and comparison. The AUC of the constructed MaxEnt model was 0.892,with good prediction accuracy. The jackknife test showed that the dominant climatic factors influencing the distribution of Ornithodoros were the minimum temperature in the coldest month and the precipitation in the driest season, with the contribution rates being 53.32% and 15.68%, respectively. The response curves showed that appropriate temperature and humidity would greatly increase the probability of occurrence of Ornithodoros. According to the model prediction map and reclassification results, under current climatic conditions, the suitable habitats of Ornithodoros in Xinjiang were mainly distributed around the Tarim Basin and the Turpan Basin; the areas of the most suitable habitats and highly suitable habitats were 84 900 km2 and 119 900 km2, respectively; the total area of the suitable habitats accounted for about 30.01% of the total area of Xinjiang. Under the ssp245 climate scenario, the most suitable area would increase to 93 700 km2 in 2021-2040, and the highly suitable area would increase to 134 200 km2 in 2081-2100.Conclusions Temperature is the most important factor influencing the distribution of Ornithodoros. The most suitable area and highly suitable area of Ornithodoros would increase under future climate scenarios.
    • Investigation
  • Seroprevalence of dengue-specific IgG antibodies 12 years after Dengue virus infection
    CHEN Jin-hua, LUO Shu-ying, LIU Ying, LING Feng, SUN Ji-min
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 679-681. https://doi.org/10.11853/j.issn.1003.8280.2023.05.016
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    Objective To investigate the seroprevalence of IgG antibodies among individuals with different characteristics 12 years after Dengue virus infection, so as to provide a scientific basis for the prevention of severe dengue fever.Methods In October 2021, serum samples were collected from symptomatic and asymptomatic cases in the 2009 dengue outbreak in Yiwu, Zhejiang Province, China. IgG antibodies to Dengue virus in the samples were measured using indirect enzyme-linked immunosorbent assay. The positive rates of IgG antibodies in populations with different characteristics were calculated and compared using the Chi-squared test. Multivariable logistic regression analysis was used to analyze the factors affecting the positive rate of the antibodies. R 4.2.1 was used for statistical analysis.Results A total of 123 samples were collected from individuals infected with Dengue virus in the outbreak, of which 101 samples were positive for dengue virus-specific IgG antibodies, with a positive rate of 82.11%. Among the investigated individuals, 57 were asymptomatic cases, with a positive rate of 64.91% (37/57), and 66 were symptomatic cases, with a positive rate of 96.97% (64/66). The positive rate of the symptomatic cases was significantly higher than that of the asymptomatic cases (χ2=21.401, P<0.001). There were 41 male and 82 female participants, with the positive rates being 85.37% (35/41) and 80.49% (66/82), respectively. Fourteen cases were ≤40 years old when they infected with Dengue virus in 2009, with 12 cases were positive; 58 cases were aged 41-60 years, with a positive rate of 81.03% (47/58); and 51 cases were ≥60 years old, with a positive rate of 82.35% (42/51). The logistic regression analysis showed a significant association between the type of infected individuals and the presence of the antibodies. The odds ratio of antibody positivity of symptomatic cases relative to asymptomatic cases was 17.30 (95% confidence interval: 3.83-78.21).Conclusions The positive rate of the IgG antibodies was still high 12 years after Dengue virus infection, which was significantly higher in symptomatic cases than in asymptomatic cases. Individuals with past Dengue virus infection have a high risk of being severe once they are re-infected.
  • A survey of the resistance of Aedes albopictus to commonly used insecticides in Weifang,Shandong Province,China
    HUO Xi-yuan, DING Shu-gang, LI Dong-ying, YUAN Sen-mei, WANG Hong-wei, HAN Xue-feng
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 682-685. https://doi.org/10.11853/j.issn.1003.8280.2023.05.017
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    Objective To investigate the resistance level of Aedes albopictus to commonly used insecticides in Weifang,Shandong, China, so as to provide a reference for the scientific use of insecticides.Methods The larval dipping method was used to determine larval deaths, the SPSS 19 software was used to caculate the toxic regression equation and the median lethal concentration (LC50) of insecticides on the larvae at the late 3rd instar and the early 4th instar, and WHO tube method was used to measure the 24 h mortality rate of healthy female mosquitoes without blood-sucking.Results The larvae of Ae. albopictus showed a resistance ratio of 3.07-6.52 fold to permethrin,propoxur,and temephos and a resistance ratio of 12.40-18.40 fold to Bacillus thuringensis israelensis (Bti, 7 000 ITU/mg). Adult mosquitoes developed resistance to 0.08% beta-cypermethrin, 0.4% permethrin,0.07% lambda-cyhalothrin,and 0.03% deltamethrin, with a 24 h mortality rate of 15.94%-62.32%. The mosquitoes were determined as possibly resistant to 0.2% fenitrothion in 2022 (with a mortality rate of 92.65%) and were determined as sensitive to 0.5% malathion, 2% chlorpyrifos, 0.2% fenitrothion, 0.2% bendiocarb, and 0.05% propoxur, with a mortality rate of 98.63%-100%.Conclusions Ae. albopictus mosquitoes in Weifang have developed serious resistance to most pyrethroid insecticides. Therefore,local use of insecticides for the prevention and control of mosquitoes should be adjusted according to surveillance results of insecticide resistance, and integrated measures, mainly environmental management, should be implemented. In addition, different insecticides should be used alternatively or in combination, so as to prevent and delay the development of insecticide resistance.
  • A rodent surveillance system based on intelligent internet of things in western agricultural area of Inner Mongolia Autonomous Region, China： Standby time and associated correlation analysis
    GUO Cheng-de, QIN Meng, HAN Li-liang, FU He-ping, LIU Bao-yu, SU Yuan-hong, XIAO Cai-hong, Alata, LIN Yong-sheng, DUAN Rui, WANG Deng-yun, QIAO Jing-ran
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 686-690. https://doi.org/10.11853/j.issn.1003.8280.2023.05.018
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    Objective To analyze the standby time of an intelligent rodent surveillance system and its influencing factors in Bayannur in western Inner Mongolia Autonomous Region (Inner Mongolia), China from September 2019 to December 2022, and to determine the correlation between rodent density and standby time.Methods Rodents were monitored using the intelligent internet of things terminal system VIMS 4.0. Statistical analysis was performed using Excel 2016 on the days of normal standby operation, number of rodents videoed, rodent density, standby time, and other indicators of the intelligent terminals, by different aspects (the first rodents of the same species, counties/banners, and different risk levels regions).Results A total of 231 rodents of eight species were detected by 10 effective terminal systems at three effective monitoring sites during the total effective monitoring time of 2 730 d. The top five most common species were Phodopus roborovskii, Meriones meridianus, Spermophilus alaschanicus, Cricetulus barabensis, and Mus musculus. The overall rodent density was 8.46%, and the mean activity frequency was 2.54 rodents/month·terminal system. The dominant species was P. roborovskii, which accounted for 57.58%. The standby time averaged 118.20 d, and ranged from 21 d to 329 d, mostly in 21-98 d, indicating a long standby time. The first rodents crossing the terminals involved four species. For terminals with the same species of the first rodents: in the descending order of rodent density, the top three species of the first rodents were Mu. musculus, S. alaschanicus, and Me. meridianus; in the ascending order of mean standby time, the top three species of the first rodents were Mu. musculus, S. alaschanicus, and Me. meridianus. The mean standby time of the terminals with the same species of the first rodents was moderately correlated with rodent density (r=-0.634); the standby time was moderately correlated with rodent density in the area without definite risk levels (r=-0.533).Conclusion This study first demonstrated a significant negative correlation between the mean standby time and rodent density in a certain space range and at a certain time scale.
  • An investigation of intestinal pathogens carried by common fly species in Pudong New Area, Shanghai, China
    LIN Chen, LIU Jun, YU Si-yu, YUAN Yong-ting, LIU Jing-yi, LU Xin-chen, HU Chen-xi, LIU Hong-xia, LIU Han-zhao
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 691-696. https://doi.org/10.11853/j.issn.1003.8280.2023.05.019
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    Objective To investigate intestinal pathogens carried by common fly species in Pudong New Area, Shanghai, China, so as to provide scientific evidence for the control of flies and associated infectious diarrhea diseases.Methods In the last ten days of each month from April to November 2021, Musca domestica flies were netted in rural houses and farmers' markets and around restaurants, and Lucilia sericata and Sarcophaga peregrina flies were netted in parks, residential areas, and farmers' markets. The flies collected were frozen for classification and identification. The microfluidic chip V3 for gastrointestinal infection was used to detect pathogens related to infectious diarrhea diseases. Excel 2019 and SPSS 22.0 were used for statistical analysis.Results A total of 1 544 M. domestica, 642 L. sericata, and 509 S. peregrina flies were captured. The pathogen detection rates of M. domestica, L. sericata, and S. peregrina were 37.29% (44/118), 67.50% (27/40), and 70.97% (22/31), respectively, which were statistically different (χ2=17.936, P<0.001). There were statistical differences in the detection rates of bacteria and viruses between the three fly species (χ2=44.547, P<0.001; χ2=26.519, P<0.001). A total of 11 types of pathogens (six species of bacteria, three species of viruses, and two species of parasites) were detected in M. domestica, mainly including Blastocystis hominis (42.37%), Sapovirus (20.34%), and Cryptosporidium (10.17%). A total of 12 types of pathogens (seven species of bacteria, three species of viruses, and two species of parasites) were detected in L. sericata, mainly including Shiga toxin-producing Escherichia coli (STEC, 18.75%), Astroviruses (13.75%), and Sapovirus (11.25%). A total of 10 types of pathogens (five species of bacteria, three species of viruses, and two species of parasites) were detected in S. peregrina, mainly including STEC (22.22%), Astroviruses (14.81%), and Sapovirus (14.81%). The pathogen detection rate of M. domestica was the lowest in Pudong New Area. The pathogens carried by M. domestica were different from those carried by the other two species.Conclusions The common fly species in Pudong New Area carried a variety of intestinal diarrhea diseases-associated pathogens, and the species of pathogens differed in different fly species. Environmental management should be strengthened and scientific fly control strategies should be formulated.
  • An epidemiological survey of animal plague in Meriones unguiculatus plague foci of Inner Mongolia Autonomous Region, China, 2018-2022
    HAN Bing, LIU Hui-jie, ZHANG Da-yu, FENG Yi-lan, LI Jian-yun, ZHANG Zhong-bing
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 697-702. https://doi.org/10.11853/j.issn.1003.8280.2023.05.020
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    Objective To analyze the epidemiological characteristics of animal plague in the Meriones unguiculatus plague foci of the Inner Mongolia Autonomous Region (IMAR), China, so as to provide a scientific basis for plague prevention and control strategies.Methods Descriptive epidemiological methods were used to analyze the surveillance data on the density of M. unguiculatus, the number of vectors, etiology, and serology of M. unguiculatus in the plague foci of IMAR from 2018 to 2022.Results In the M. unguiculatus plague foci of IMAR from 2018 to 2022, the mean density of M. unguiculatus was 2.45 individuals/hm2, the flea infestation rate of M. unguiculatus was 23.96%, and the flea index was 0.62. Yersinia pestis was isolated for five consecutive years. The Y. pestis detection rate of animals was 0.39%. The Y. pestis detection rate of vectors was 0.29%. The serological positive rate by indirect hemagglutination assay was 0.21%.Conclusions Plague was active in the M. unguiculatus plague foci of IMAR from 2018 to 2022. Routine surveillance should be strengthened to timely detect and control animal plague, so as to effectively reduce the intensity of animal plague and the risk of human plague.
  • Spatial distribution of rodent fleas in the plague foci of Ordos, China, 2014-2022
    FENG Yi-lan, LI Jian-yun, ZHANG Da-yu, YU Xin-xin
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 703-707. https://doi.org/10.11853/j.issn.1003.8280.2023.05.021
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    Objective To analyze the species composition, spatial distribution, and Yersinia pestis infection status of fleas in the plague foci of Meriones unguiculatus in Ordos of the Inner Mongolia Autonomous Region (Inner Mongolia), China, so as to provide a basis for local plague prevention and control.Methods The surveillance data of rodent body fleas were collected in five banners/districts of the M. unguiculatus plague foci in Ordos in Inner Mongolia from 2014 to 2022. Excel 2019 was used for data processing, and ArcGIS 10.5 was used for mapping. The species, numbers, and Y. pestis infection status of fleas in different years and different regions were analyzed.Results A total of 17 010 fleas belong to 14 species in 9 genera under 4 families were collected. The annual numbers of flea species collected ranged from 4 to 11, with a mean number of 8.30 species per year. The annual numbers of fleas collected ranged from 563 to 3 158, with a mean number of 1 890 fleas per year. The dominant flea species were Xenopsylla conformis conformis and Nosopsyllus laeviceps. The mean annual flea infestation rate of M. unguiculatus was 33.48%, with a flea index of 0.92. The flea index was highest in Hangjin Banner and lowest in Wushen Banner. There were four years during which a total of 19 strains of Y. pestis were isolated from 125 fleas of three species in two banners/districts.Conclusion In recent years, there have been outbreaks of animal plague in the plague foci of M. unguiculatus in Ordos, especially in Otog Banner, Otog Front Banner, and Hangjin Banner, with a high risk of transmission via bites from infected fleas to humans.
    • Review
  • Research advances in effects of insecticide resistance on mosquito vector competence
    WU Jia-hui, PENG Hui, GONG Mao-qing
    Chinese Journal of Vector Biology and Control. 2023, 34(5): 708-712. https://doi.org/10.11853/j.issn.1003.8280.2023.05.022
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    The spread of mosquito-borne viral diseases seriously endangers public health security. Chemical control of mosquitoes is an effective means of controlling mosquito-borne diseases,but global continuous overuse of insecticides has led to the development and progression of insecticide resistance,which can affect the vector competence of some mosquitoes for mosquito-borne viruses. A large body of research has assessed the impact of insecticide resistance of mosquito vectors on their viral transmissibilty. This review focuses on research progress on the dynamic relationship between mosquito vector competence and insecticide resistance as well as the mechanisms associated with the change of vector competence due to insecticide resistance, with a view to providing a reference for future resistance research and vector control.
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