20 June 2020, Volume 31 Issue 3
    

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    Dengue Fever Surveillance and Control Special
  • A preliminary study on the current awareness of dengue fever in residents of Jinghong, Xishuangbanna prefecture, Yunnan province, China
    ZHAO Zhong-hui, YUE Yu-juan, WU Hai-xia, GUO Yu-hong, ZHAO Ning, REN Dong-sheng, YANG Ming-dong, WANG Jun, XIE Lyu, JIANG Jin-yong, LIU Qi-yong, LIU Xiao-bo
    Chines Journal of Vector Biology and Control. 2020, 31(3): 249-253. https://doi.org/10.11853/j.issn.1003.8280.2020.03.001
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    Objective To investigate the current status of residents' awareness of dengue in Jinghong, Xishuangbanna Dai autonomous prefecture (Xishuangbanna prefecture), Yunnan province, China, and to provide a scientific basis for the establishment of accurate response mechanism and the sustainable control of dengue. Methods A representative grid was selected randomly from the grids with dengue prevention and control during the period of dengue outbreak in Jinghong in 2019. A questionnaire survey was conducted among the residents in the grid in a one-to-one question- and-answer manner. SPSS 20.0 statistical software was adopted for the statistical analysis. Results A total of 249 valid questionnaires were collected. The chi-square analysis revealed that urban residents paid more attention to dengue-related knowledge than rural residents (χ2=12.444, P=0.040). The education system staff and the highly educated ones paid more attention to the knowledge of mosquito control. Residents with different occupations, monthly average income levels, and levels of education chose different ways of seeking medical treatment if they were inadvertently infected with dengue. The highly educated ones, those high-income earners, and the education system staff were more inclined to go to the grade A tertiary hospitals. Urban residents held the view that there were more dengue infections around themselves than around rural residents. The highly educated population had a higher proportion of people who thought they had enough knowledge of dengue prevention and control than the less educated population. The results of unconditional logistic regression analysis demonstrated that residents with different ages, levels of education, and current places of residence showed different abilities to use new media to acquire knowledge about dengue prevention and control. Conclusion In Jinghong, Xishuangbanna prefecture, the elderly, the rural residents, the less educated people, and the low-income earners had a relatively low level of awareness of dengue. It is suggested that in future, the above-mentioned populations should be focused on in the establishment of local accurate response mechanism and the scientific prevention and control of dengue.
  • Effectiveness evaluation of the gridding management of dengue fever in the urban area of Jinghong, Yunnan province, China
    TANG Ye-rong, JIANG Jin-yong, DU Long-fei, YANG Ming-dong, FAN Jian-hua, ZHU Jin, ZOU Jian-hong, HE Jing, YU Zhang, ZHOU Hong-ning
    Chines Journal of Vector Biology and Control. 2020, 31(3): 254-258. https://doi.org/10.11853/j.issn.1003.8280.2020.03.002
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    Objective To investigate the application effect of gridding management in the prevention and control of dengue fever in Jinghong, Yunnan province, China, and to provide a scientific basis for developing effective prevention and control strategies for dengue fever. Methods Based on the gridding management system of dengue fever prevention and control in Jinghong in 2019, epidemiological description and the geographic information system were used to analyze and evaluate the effectiveness of gridding management in the prevention and control of dengue fever in Jinghong in 2019. Results In 2019, 28 dengue fever grid points were divided in the urban area of Jinghong city. Imported cases occurred in June, the outbreak of dengue fever was observed in July, and the cases of dengue fever reached the peak in September (1 775 cases). For the 28 grid points in Jinghong from June to November, the monthly mean Breteau index (BI) was 11.18, 18.42, 14.62, 14.02, 5.81, and 2.09, respectively, the rate of reaching the standard of BI was 52.56%, 44.76%, 51.66%, 46.57%, 74.01%, and 91.71%, respectively, and the number of dengue cases were 8, 47, 540, 1 775, 473, and 72, respectively. Conclusion Gridding management can effectively prevent and control dengue fever by improving the rate of reaching the standard of BI in the urban area of Jinghong. It is suggested that the local government should further develop the grid management of dengue fever.
  • Effectiveness evaluation of government-purchased vector control services for the prevention and control of dengue fever
    LI Xiao-ning, LIU Yuan, CHEN Zong-qiu, JIANG Yi-min, LIU Jie, LIANG Xue-ying, LI Yi-lan, ZHAO Zheng-yang, ZHANG Xu, LIN Yun-wan, LUO Lei
    Chines Journal of Vector Biology and Control. 2020, 31(3): 259-262. https://doi.org/10.11853/j.issn.1003.8280.2020.03.003
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    Objective To evaluate the dengue prevention and control effectiveness of government-purchased vector control services and to perfect the pattern of government-purchased pest control services in the emergency management of dengue. Methods We systematically collected the data about dengue cases, the assessment of epidemic foci, and the management and evaluation from the municipal mosquito vector control team for emergency response in Guangzhou, Guangdong province, China, 2019. We assessed the effectiveness of the team's performance by epidemic duration and cumulative case number at the epidemic focus. The rank sum test was used to analyze whether the epidemic situation was affected by the response, also different response, from the team. Results In 2019, a total of 1 478 local cases were reported in Guangzhou, distributed in 680 epidemic foci, including 143 (21.03%) foci of outbreaks. The team dealt with 28 epidemic foci, accounting for 4.12% of the total foci. The density of adult mosquitoes was significantly reduced after mosquito vector control from the team (t=6.909, P<0.001). Both the epidemic duration and case number were significantly lower in the foci where the treatment began within eight days after the epidemic emerged and there were at least two round actions than in the foci without the treatment (Z=3.984, 2.345, 2.048, and 3.586, all P<0.05). Conclusion Early and full-scale control of mosquitoes at dengue epidemic foci by the municipal mosquito vector control team for emergency response, in the form of government-purchased services, can contain the community spread of dengue. In future dengue prevention and control by mosquito vector control, more personnel should be added, and other control forces should be united to establish an effective mechanism of surveillance, evaluation, and emergency response.
  • Surveillance of insecticide resistance and density of the dengue vector Aedes albopictus in four prefectures of Zhejiang province, China, 2018
    LIU Qin-mei, HOU Juan, WEI Ling-ya, MA Min, ZHONG Jian-yue, WU Yin-ping, WANG Jin-na, WU Yu-yan, LI Tian-qi, GONG Zhen-yu
    Chines Journal of Vector Biology and Control. 2020, 31(3): 263-267. https://doi.org/10.11853/j.issn.1003.8280.2020.03.004
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    Objective To investigate the density fluctuation of the dengue vector Aedes albopictus and its resistance to commonly used insecticides in four regions of Zhejiang province, China, and to provide a basis for rational selection and use of insecticides and scientific prevention and control of dengue. Methods The density of adult Ae. albopictus was monitored by the double mosquito net method in four cities of Hangzhou, Ningbo, Quzhou, and Yiwu in Zhejiang province from April to November of 2018. The larvae were collected and reared to adults for determining resistance using the diagnostic doses of insecticides. Results The annual average net trap index was 1.33 mosquitoes/net·hour in the four prefectures of Zhejiang province, and that was 1.60 mosquitoes/net·hour in residential areas, which was the highest among three habitats. The Ae. albopictus population of Hangzhou was sensitive to three pyrethroids and malathion, and showed suspected resistance to propoxur. The mosquito population of Ningbo showed sensitive to beta-cypermethrin, suspected resistance to deltamethrin, permethrin, and propoxur, and resistance to malathion. The Ae. albopictus populations of Quzhou and Yiwu were sensitive to malathion, and exhibited suspected resistance to three pyrethroids and propoxur. Of the mosquito populations of the four cities, 5.00%, 60.00%, and 35.00% showed resistance, suspected resistance, and sensitivity to five insecticides, respectively. Conclusion In the four cities of Zhejiang province, the density of Ae. albopictus in residential areas and parks peaks in July. The mosquitoes develop varying degrees of resistance to the tested insecticides. Strengthening the surveillance of their density fluctuation and insecticide resistance contributes to slowing the development of resistance and effectively controlling dengue.
  • An analysis of emergency surveillance results of Aedes vector before mosquito control in the epidemic areas of dengue fever outbreak in Chongqing, China, 2019
    XIAO Han-sen, HE Ya-ming, SHEN Tian-zhanhong, WANG Yi-qi, YANG Xue-fan, TU Tao-tian, JI Heng-qing
    Chines Journal of Vector Biology and Control. 2020, 31(3): 268-271. https://doi.org/10.11853/j.issn.1003.8280.2020.03.005
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    Objective To investigate the results of emergency surveillance of Aedes vector before mosquito control after the occurrence of the index case of dengue fever in the epidemic areas of Chongqing, China, and to provide a basis for future surveillance of Aedes vector and early warning research on the risk of local transmission of dengue fever. Methods The surveillance data of Aedes vector were collected after the first cases of dengue fever were reported and before the mosquito control measures were adopted in each epidemic area of Chongqing, including Breteau index (BI) and double mosquito net index (DMNI), and SPSS 25.0 software was used for data description and linear regression analysis. Results The average BI for the first-time emergency surveillance in all epidemic areas was 11.01, and the average was 5.10 mosquitoes/net·hour, with a positive correlation between the two indices (r=0.517, P<0.05). The bivariate linear regression analysis was used to establish the regression equation of BI and DMNI:y (BI)=7.07+0.82x (F=61.232, P<0.005), and the early warning of dengue fever risk in Chongqing was stratified into four levels based on this equation. Conclusion Graded assessment of BI and DMNI acts as an indicator for the early warning of dengue fever risk. For Chongqing, BI controlled below 7 and DMNI controlled below 3 mosquitoes/net·hour may reduce the risk of local outbreak of dengue fever.
    • Original Reports
  • Analysis of molecular epidemic characteristics of Jingmen tick virus among ticks in northern China
    YU Zhu-mei, XIONG Yan-wen, WANG Wen, ZHANG Yong-zhen
    Chines Journal of Vector Biology and Control. 2020, 31(3): 272-276. https://doi.org/10.11853/j.issn.1003.8280.2020.03.006
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    Objective To investigate the molecular epidemic characteristics of Jingmen tick virus (JMTV) among ticks in northern China by genome amplification and phylogenetic analysis. Methods Ticks samples were collected to prepare tick homogenate and extract total RNA. RT-PCR was used for genome amplification of JMTV. Sequence comparison and phylogenetic analysis were performed. Results A total of 277 ticks collected from 3 provinces (Bole city in Xinjiang, Shenyang city in Liaoning, and Changping district in Beijing) were screened for JMTV, and 67 positive samples were observed, with a positive rate of 24.2%. Four strains of JMTV with nearly full-length genome were obtained. Based on the results of the phylogenetic analysis, the segments 1, 2, and 4 of these 4 strains clustered with the rodent-borne JMTV from Xinjiang. The segment 3 of 2 strains clustered with the rodent-borne JMTV from Xinjiang, but the other 2 strains clustered with the tick-borne JMTV from other regions of China, which suggest the possibility of gene reassortment. Conclusion Based on the homology analysis, the newly discovered 4 JMTV strains have the highest homology with the known JMTV in China, with genetic diversity.
  • Investigation of malaria infection rate among Chinese staffs and evaluation of the effect of training on mosquito vector control in Sierra Leone, 2019
    ZHAO Ning, TU Hong, GUO Yu-hong, LIU Xiao-bo, REN Dong-sheng, LUO Wei, ZOU Xiao-hui, ZHAO Ying-ze, ZHENG Xiao, SUN Yong, LIU Yang, MA Jiang-tao, WAN Jia-yu, WANG Li-li, DUAN Zhao-jun, LIU Qi-yong
    Chines Journal of Vector Biology and Control. 2020, 31(3): 277-281. https://doi.org/10.11853/j.issn.1003.8280.2020.03.007
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    Objective To investigate the malaria infection rate among Chinese staffs of Chinese-funded institutions in Sierra Leone and train them to acquire comprehensive knowledge of malaria vector control. Methods Chinese-funded institutions selected their staffs to receive training on malaria vector control. Using the cluster sampling method, a questionnaire survey was conducted among all 134 trainees before the training course started. The trainer taught the knowledge of malaria vector control face to face using PPT (PowerPoint), and the trainees learned about the principal vector of malaria in Sierra Leone, Anopheles gambiae, and its characteristics and habits through the study of mosquito specimens. After the training, the questionnaire of malaria vector control knowledge was used again to evaluate the training effect. The results of questionnaire survey were analyzed statistically using the t test and chi-square test. Results The mean awareness score of mosquito vector control knowledge was 31.46±20.68 before training and 85.98±16.33 after training, with a significant improvement (F=565.636, P<0.001). The investigation showed that the malaria infection rate average among trainees in the past year was 29.10%, significantly higher in outdoor workers than in indoor workers (37.40% vs 5.70%, χ2=12.561, P<0.001). The analysis of correlation between trainees' pre-training scores and malaria infection rate showed that compared with the highly educated staffs, those with a lower education level had the lower mean score and a significantly higher malaria infection rate (χ2=6.152, P=0.046). The pre-training scores showed a negative correlation with the malaria infection rate. Conclusion In Sierra Leone, the training on mosquito vector control knowledge should be strengthened among the staff members of Chinese-funded institutions, especially those working outdoors and those with a lower education level. Training plans should be developed based on local mosquito vector surveillance data and malaria epidemic situation, and training on relevant mosquito vector control knowledge should be conducted regularly for the Chinese staffs abroad so that they can protect themselves from mosquito-borne diseases such as malaria.
  • Epidemiological characteristics of scrub typhus and genotyping of the pathogen Orientia tsutsugamushi in Chuxiong prefecture, Yunnan province, China
    HU Ting-song, LI Ying, HU Qiu-ling, WU Xue-lin, GAO Li-fen, LI Guo-wei, WANG Zhi-yong, HU Hai-mei, WANG Yi-yin, ZHANG Hai-lin, ZHANG Fu-qiang
    Chines Journal of Vector Biology and Control. 2020, 31(3): 282-288. https://doi.org/10.11853/j.issn.1003.8280.2020.03.008
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    Objective To investigate the epidemiological characteristics of scrub typhus in Chuxiong Yi autonomous prefecture (Chuxiong prefecture), Yunnan province, China, and to analyze the genotypes of the pathogen Orientia tsutsugamushi (Ot). Methods The data of scrub typhus cases were collected for epidemiological analysis. Blood samples from the patients were obtained to detect the nucleic acids of Ot by PCR and sequence the Tsa56 gene. Homology and phylogenetic analyses were performed using bioinformatics software. Results A total of 2 507 cases of scrub typhus were reported in Chuxiong prefecture from 2015 to 2018, with a mean annual incidence of 22.79/100 000. Scrub typhus occurred in all 10 counties/cities of the prefecture, and 96.01% (2 407/2 507) of the total cases were distributed in Chuxiong, Dayao, Yongren, Nanhua, and Shuangbai counties/cities. The cases occurring during July to October accounted for 88.35% (2 215/2 507) of the total number. The male-to-female ratio was 1:1.34. The majority of the patients were aged from 30 to 69 years (78.42%, 1 966/2 507), and most cases were farmers (84.92%, 2 129/2 507). PCR detected 4 samples (CX1601, CX1602, CX1603, and CX1604) positive for Ot nucleic acids from 6 blood samples of scrub typhus patients. The Tsa56 gene was obtained for sequencing, and the homology and phylogenetic analyses showed that CX1601 and CX1604 shared high homology and close genetic relationship with the Kato strains of Ot, while CX1602 and CX1603 were highly homologous and closely related to Gilliam strains, but relatively low homology and large genetic distances with other strains. Conclusion Scrub typhus in Chuxiong prefecture belongs to Kato or Gilliam type. In recent years, there was a high incidence and an increasing trend year by year. It is necessary to strengthen the surveillance and control of the host and vector.
  • Investigation of Rickettsia typhi in small mammals in Luxi county, Yunnan province, China
    YUAN Qing-hong, YANG Xiang-dong
    Chines Journal of Vector Biology and Control. 2020, 31(3): 289-293. https://doi.org/10.11853/j.issn.1003.8280.2020.03.009
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    Objective To investigate the general status and molecular biological characteristics of Rickettsia typhi carried by small mammals in Luxi county, Yunnan province, China, as well as the national foci of typhus, and to provide a scientific basis for prevention and control of Rickettsia diseases. Methods Rat cages and rat traps were used to capture smalls in residential and wild areas in Luxi county. The captured animals were classified before their blood was collected from them alive for their sera. Indirect immunofluorescence assay was adopted to detect R. typhi antibodies in their sera. Spleens were cut off for DNA extraction and nested polymerase chain reaction (PCR) analysis to detect the groEL gene of R. typhi. Positive specimens were sequenced and analyzed by the Basic Local Alignment Search Tool (BLAST) provided by the National Center for Biotechnology Information (NCBI), and their phylogenetic trees were constructed for homology and evolution analysis. Results A total of 193 small mammals were captured in Luxi county, 64 of which were in residential areas with Rattus tanezumi as the dominant species and 129 of which were in wild areas with Eothenomys miletus and Apodemus draco as the dominant species. Eighty-three sera samples were obtained. Nested PCR analysis of their spleens found all specimens in residential areas negative and 2 specimens (LX2, LX89) in wild areas positive for the groEL gene. The positive specimens were from E. miletus, yielding a carrying rate of 1.04%. The two positive specimens were sequenced and aligned by BLAST with known sequences in GenBank. LX2 and LX89 showed 100% identity, and they displayed 100% and 98% identity with R. mooseri (GenBank AF075440), respectively. Their phylogenetic trees suggested that they were in the same branch and closely related to AF075440, AY191590,and AY191591 strains of R. mooseri. Four of eighty-three rodents' sera were positive for R. mooseri antibodies with a positive rate of 4.82%. Conclusion There are natural foci of typhus mainly hosted by E. miletus in Luxi county, Yunnan province, China.
  • Effects of intestinal culturable non-anaerobic bacteria in Musca domestica larvae on feeding and oviposition of M. domestica adults
    CHANG Rui-rui, CHEN Hai-min, CHEN Hong-min, WAN Qing, LE Qian-qian, ZHANG Rui-ling, ZHANG Zhong
    Chines Journal of Vector Biology and Control. 2020, 31(3): 294-299. https://doi.org/10.11853/j.issn.1003.8280.2020.03.010
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    Objective To investigate the effects of intestinal bacteria in Musca domestica larvae on their feeding and oviposition into the adulthood. Methods Traditional methods were used for isolation and culture of culturable non-anaerobic bacteria from the intestinal tracts of 3-day-old M. domestica larvae. These bacteria were used to carry out feeding and oviposition preference experiments on M. domestica adults. With SPSS 20.0 software for statistical analysis, one-way analysis of variance was conducted for comparison between groups, and the t-test was used for comparison between two independent samples. Results Ten bacteria belonging to 9 genera were isolated from the intestinal tracts of M. domestica larvae:Enterobacter hormaechei, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter bereziniae, Providencia stuartii, E. cloacae, Lactococcus lactis, Lysinibacillus fusiformis, P. vermicola, and Bacillus safensis. E. hormaechei, L. lactis, and E. cloacae were found to exert attracting effects on feeding of M. domestica adults, yielding attracting rates of (80.88±5.60)%, (60.77±4.13)%, and (61.59±4.13)%, respectively, and the other seven bacteria were found to inhibit feeding. Ten bacteria were all revealed to have attracting effects on oviposition of M. domestica adults. E. hormaechei, E. cloacae, L. lactis, L. fusiformis, and B. safensis showed strongest attracting effects, with attracting rates of 100%. Conclusion It has been confirmed that intestinal bacteria in M. domestica larvae have effects on their feeding and oviposition into their adulthood, and it is clarified that M. domestica adults' feeding and oviposition are mainly regulated by nutrition and odor, respectively. The results lay a foundation for research and development of new bacterial repellents or attractants of M. domestica adults.
  • Surveillance report of national rodent surveillance sites in Shandong province, China, 2010-2018
    WANG Xue-jun, SUN Qin-tong, HAN Ying-nan, GONG Xue-shi, LAI Shi-hong, ZHANG Shi-shui
    Chines Journal of Vector Biology and Control. 2020, 31(3): 300-304. https://doi.org/10.11853/j.issn.1003.8280.2020.03.011
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    Objective To investigate the common species, density, and seasonality of rodents in human settlements and the surrounding environment in Shandong province, China, and to provide a scientific basis for assessing the risk of rodent-borne diseases and for preventing and controlling rodents effectively. Methods The data of rodents from the national vector surveillance sites in Shandong province from 2010 to 2018 were collected and sorted out, the constituent ratio of rodent species was analyzed, and the rodent density and its seasonality characteristics were compared between rodents of different species and from different habitats. Results A total of 1 374 rodents were captured from 2010 to 2018, and the total density of rodents was 0.82% trap capture rate. Among the captured rodents, the constituent ratios of Rattus norvegicus, Mus musculus, and Apodemus agrarius were 48.84%, 40.68%, and 7.79%, respectively, and their densities were 0.40%, 0.33%, and 0.06%, respectively. Rattus norvegicus was the dominant species, followed by M. musculus. The rodent densities in rural residential areas, key industries, and urban residential areas were 1.16%, 0.74%, and 0.58%, respectively. The density of R. norvegicus was highest in rural residential areas and urban residential areas (0.42% and 0.35%), while the density of M. musculus was highest in key industries (0.56%). The seasonality of total density showed an atypical bimodal curve, with the peaks appearing from April to June and September to October. Apart from a slight increase in 2012, the total density of each rodent species remained stable with a slight decline in other years. The seasonality curves of rodent density in different species, habitats, and years were similar to the total density curve. Conclusion Rattus norvegicus and M. musculus are dominant rodent species in human settlements and the surrounding environment in Shandong province. The rodent density at surveillance sites in the whole province showed an overall downward trend from 2010 to 2018. May to June and September to October each year is the peak of rodent activity, and the rodent density was relatively high in rural residential areas and key industries. Rodent control in peak periods of rodent activity and in active habitats should be strengthened.
  • DNA barcoding analysis of rodents captured in Jiangmen, Guangdong province, China
    YAO Dan-dan, JIANG Hong-xue, SUI Jing-jing, FENG Zhi-yong
    Chines Journal of Vector Biology and Control. 2020, 31(3): 305-309. https://doi.org/10.11853/j.issn.1003.8280.2020.03.012
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    Objective To identify and analyze the rodents captured in the farmland in Xinhui district, Jiangmen, Guangdong province, China, using DNA barcoding technology, and to lay a foundation for the diversity study of murine-like animals and rodent prevention and control. Methods Forty-five rodents captured in the farmland in Xinhui district, Jiangmen, Guangdong province, in December 2017, were enrolled as study subjects. Their genetic DNAs were extracted and amplified for mitochondrial cytochrome c oxidase subunit I gene fragments using consensus primers. The gene fragments were sequenced and the results were subjected to sequence homology analysis using BLAST in the National Center for Biotechnology Information. The molecular evolutionary tree was constructed by the neighbor-joining method. Genetic distance was calculated based on a two-parameter model. Results Specific gene fragments of the forty-five samples were obtained by PCR amplification. Four species of rodents (Rattus losea, R. tanezumi, R. norvegicus, and R. andamanensis) were identified through BLAST comparison. Thirty-seven samples had identification results identical to the morphological identification (R. losea), and eight samples had erroneous morphological identification results, among which five were reidentified as R. tanezumi, two were reidentified as young R. norvegicus, and one was reidentified as R. andamanensis, according to the review of the initial results. A total of 131 mutation sites were identified through alignment and analysis of the 45 sequences, and 12 different haplotypes were identified through haplotype analysis. The intraspecific genetic distance of R. losea was 0-1.2%, the interspecific genetic distance was 7.1%-11.6%, and the mean genetic distance was 10.1%±0.7%. The NJ tree showed that individuals of the same rodent species were clustered into one branch with a 100% support rate, which could distinguish among different rodent species. Conclusion The DNA barcoding technology can effectively distinguish between related species with similar morphology and correct the erroneous results of morphological identification.
  • An analysis of mosquito vector surveillance results in Freetown, Sierra Leone, 2019
    ZHAO Ning, ISHAQ Sesay, TU Hong, FREDERICK Yamba, REN Dong-sheng, GUO Yu-hong, LU Liang, WU Hai-xia, LIU Xiao-bo, YUE Yu-juan, LI Gui-chang, WANG Jun, SONG Xiu-ping, WANG Li-li, DUAN Zhao-jun, LIU Qi-yong
    Chines Journal of Vector Biology and Control. 2020, 31(3): 310-315. https://doi.org/10.11853/j.issn.1003.8280.2020.03.013
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    Objective To establish the mosquito vector surveillance capacity in Freetown, Sierra Leone, and to investigate local mosquito density, geographical distribution, population characteristics, and seasonal fluctuations. Methods A total of nine zones were selected as mosquito surveillance sites in the western urban and rural areas of Freetown, Sierra Leone, with at least one site in each of residential areas, general working institutions, hospitals, and livestock sheds, and mosquito trap lamps were used for surveillance. Each surveillance site had 2-4 mosquito trap lamps, which were fixed in an outdoor place protected from wind, rain, and light at about 1.5 meters above the ground. The mosquito trap lamps were placed at 1 hour before sunset and the net was collected at 1 hour after sunrise in the next morning. Then the collected mosquitoes were classified by morphological characteristics in the laboratory. Mosquito surveillance was conducted once a week from June 26, 2019 to December 31, 2019. Excel 2007 software was used for the statistical analysis of mosquito vector surveillance data. Results A total of 3 012 mosquitoes were collected, among which Culex mosquitoes accounted for 84.86% and was the dominant mosquito genus in Freetown. Compared with the western urban areas, the western rural areas had significantly higher mean total mosquito density (5.01 mosquitoes/trap·night vs 3.87 mosquitoes/trap·night), mean Anopheles density (1.28 mosquitoes/trap·night vs 0.12 mosquitoes/trap·night), and composition ratio of Anopheles (1.14%-44.53% vs 0.72%-11.90%). Seasonal fluctuations of mosquito density showed that in Freetown, high mosquito density was observed during the alternate period of dry and rainy seasons in late June and early July and during the alternate period of rainy and dry seasons in late October and early November, and the lowest mosquito density was observed in late August. In addition, the seasonal fluctuation trend of Anopheles density was consistent with that of total mosquito density. A comparative analysis of different habitats showed that the livestock sheds with poor environmental sanitation and more mosquito breeding sites had a higher mosquito density (10.40 mosquitoes/trap·night), followed by residential areas (4.45 mosquitoes/trap·night) and general working institutions (2.80 mosquitoes/trap·night), and the hospitals with better environmental sanitation and fewer breeding sites had the lowest mosquito density (1.21 mosquitoes/trap·night). Conclusion The risk of mosquito bite and malaria infection in the western rural area is higher than that in the western urban area. The alternate periods from the dry season to the rainy season and from the rainy season to the dry season are important periods for the prevention and control of mosquito vectors and their infectious diseases (including malaria). Sierra Leone needs to further strengthen the management of mosquito breeding sites.
  • Distribution and population density of Aedes albopictus in Xuzhou, Jiangsu province, China, 2018
    MA Zhuang-xuan, QIN Yan-wei, DENG Pu-zhou, LU Yao, YUAN Fei, HE Cheng, XU Jia-bao, LI Yi-ji, LIU Zhuan-zhuan
    Chines Journal of Vector Biology and Control. 2020, 31(3): 316-320. https://doi.org/10.11853/j.issn.1003.8280.2020.03.014
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    Objective To investigate the distribution and population density of Aedes albopictus in Xuzhou, Jiangsu province, China, and to evaluate the risk of outbreak of dengue fever in Xuzhou. Methods From January to December 2018, Ae. albopictus mosquitos were continuously surveyed by mosquito ovitraps. The differences in mosquito ovitrap index (MOI) between Ae. albopictus in different months, habitats, and regions were analyzed by the χ2 test to observe their seasonal fluctuation in Xuzhou and the variation of their distribution in different habitats and regions. Results According to the surveillance data in 2018, the distribution of Ae. albopictus varied between different months, habitats, and regions. Aedes albopictus began to appear in May, and their density mounted to the peak in August (MOI=64.24), followed by a gradual decline. During mosquito seasons, their density was the highest in the residential areas (MOI=36.33) and showed no significant difference between parks and schools (MOI:28.19 vs 24.62, χ2=1.722, P=0.107). Aedes albopictus MOI showed significant differences between residential and non-residential areas in June (χ2=4.591, P=0.038), September (χ2=18.100, P=0.001) and October (χ2=3.734, P=0.035). Comparison of MOI of Ae. albopictus in Yunlong, Tongshan, Kaifa, and Gulou districts of Xuzhou in 2018 found significant differences between Yunlong and Kaifa districts (χ2=21.010, P<0.01), Kaifa and Gulou districts (χ2=19.700, P<0.01), and Kaifa and Tongshan districts (χ2=12.500, P<0.01). The MOI in Kaifa district (MOI=41.08) was the highest. Conclusion The monitoring of Ae. albopictus should be strengthened in Xuzhou, particularly in residential areas. Sensitive, scientific, and objective surveillance methods should be adopted for timely detection, and prevention and control of increase in Ae. albopictus density can effectively reduce the risk of the mosquito-borne disease outbreak in Xuzhou.
  • Distribution and population density fluctuation of Aedes albopictus in Minhang district, Shanghai, China
    ZHU Min-hui, LIU Li-jun, WU Min, LYU Jing, ZHANG Zhao-wen, LIU Hong-xia
    Chines Journal of Vector Biology and Control. 2020, 31(3): 321-324. https://doi.org/10.11853/j.issn.1003.8280.2020.03.015
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    Objective To grasp the environmental distribution and density fluctuation of Aedes albopictus in Minhang district, Shanghai, China, and to provide a reference for scientific prevention and control of dengue epidemic. Methods From May to October 2018, the Breteau index (BI) method and the mosquito ovitrap index (MOI) method were applied to monitor Ae. albopictus larvae in residential areas, hospitals, and schools, and from April to November 2018, the carbon dioxide trapping method was adopted to monitor adult Ae. albopictus in residential areas, rural households, and hospitals, in order to observe the distribution characteristics and population density fluctuation of Ae. albopictus in different seasons. Results Both BI and MOI in Minhang district showed a unimodal trend. BI peaked in July (peak value 17.82) and MOI peaked in August (peak value 13.50). Both indices were found highest in schools and kindergartens (BI:17.57; MOI:11.84). Adult Ae. albopictus density measured by the carbon dioxide trapping method showed a unimodal trend. The peak value (2.40) was observed in August, and the highest density (3.84) was found in residential areas. Conclusion During the peak period of dengue epidemic, scientific and effective methods should be adopted to monitor the density fluctuation of Ae. albopictus, and comprehensive control should be carried out based on the monitoring data to effectively prevent outbreak of dengue fever in the local area.
  • Seasonal variation of mosquito density and species diversity in Tangshan,Hebei province, China, 2007-2018
    YUN Ling, WANG Fu-cai, LI Shu-shuang, GAO Qing-hua, WANG Xiu-ying, SHANG Xiu-li, CHAO Yi-shu, LIU Yuan-yuan, DONG Rong-xuan
    Chines Journal of Vector Biology and Control. 2020, 31(3): 325-330. https://doi.org/10.11853/j.issn.1003.8280.2020.03.016
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    Objective To investigate the seasonal variation of mosquito density and species diversity of mosquitoes in Tangshan, China, and to provide a scientific basis for effective mosquito prevention and control. Methods The mosquito surveillance data were obtained, using the light-trap method, from five surveillance sites in urban residential areas, parks, hospitals, suburban residential areas, and livestock sheds, in Tangshan, from May to October of each year during 2007-2018. The data were then used for measurement, comparison, and analysis of the density, species diversity, and seasonal variation of mosquitoes in different years/months and habitats. In this study, the Shannon-Wiener diversity index, Pielou uniformity index, Berger-Parker dominance index, and relative species abundance were used to study the diversity of mosquitoes. Results A total of 10 mosquito species were captured, i.e., Culex pipiens pallens, Cx. tritaeniorhynchus, Cx. modestus, Cx. vagans, Cx. fuscanus, Aedes albopictus, Ae. vexans, Ae. dorsalis, Anopheles sinensis, and An. yatsushiroensis. The mosquito density was 1.70 mosquitoes/light·hour, with the highest density observed for Cx. pipiens pallens (1.65 mosquitoes/light·hour). The composition of different mosquito species was different in different years (χ2=3 393.930, P<0.001). Among the different habitats, livestock sheds had the highest density of 2.94 mosquitoes/light·hour. According to the analysis of species diversity indices in different habitats, the diversity index and uniformity index of residential areas were the highest (0.23 and 0.14, respectively), and the dominance index of rural residential areas was the highest (0.98). The seasonal variation curve of mosquito density was unimodal, with a peak (3.75 mosquitoes/light·hour) observed in July. The species diversity index and uniformity index were the highest in August (0.31 and 0.17, respectively), and the dominance index was the highest in October (0.99). Conclusion Culex pipiens pallens is the dominant mosquito species in Tangshan. The highest mosquito density was observed in livestock sheds, and the mosquito species were most abundant in residential areas, with the most uniform density of different mosquito species. The highest dominance index was observed in rural houses. The highest mosquito density was observed in July, and the mosquito species was most abundant in August, with the most uniform density of different mosquito species, the highest dominance index was observed in October.
  • Expression level of olfactory receptor 10 gene in Aedes albopictus before and after blood sucking
    HUANG Xiao-dan, YANG Lin-lin, LIU Lu-hong, CHENG Peng, LIU Hong-mei
    Chines Journal of Vector Biology and Control. 2020, 31(3): 331-334. https://doi.org/10.11853/j.issn.1003.8280.2020.03.017
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    Objective The olfactory system plays an important role in mosquito behaviors such as blood sucking and oviposition site selection. This study compared the expression level of odorant receptor 10 gene (OR10) in Aedes albopictus before and after blood sucking. Methods Reverse transcription-polymerase chain reaction (RT-PCR) was performed to amplify the OR10 gene, and quantitative real-time PCR was used to determine the expression levels of OR10 gene in male Ae. albopictus, and female Ae. albopictus before and after blood sucking. Results The open reading frame of the OR10 gene in Ae. albopictus obtained by amplification was 1 128 bp in length, encoding 376 amino acids. The amino acid sequence had an identity of 86.13% and 69.69%, respectively, with that in Ae. aegypti and Anopheles gambiae. The results of quantitative real-time PCR showed that male Ae. albopictus had the lowest expression level of OR10 gene of 1; female Ae. albopictus had a higher expression level (1.535±0.274) than male Ae. albopictus; female Ae. albopictus had the highest expression level of OR10 gene (2.284±0.203) after blood sucking; the expression level of OR10 gene in female Ae. albopictus changed significantly before and after blood sucking (F=32.067, P=0.001). Conclusion The expression level of OR10 in Ae. albopictus changes significantly before and after blood sucking, which further proves that OR10 may be involved in the mosquito behavior of oviposition site selection after blood sucking.
    • Taxonomy and Fauna of Vectors Report Series
  • Taxonomy and fauna of Siphonaptera in Tibet autonomous region, China Ⅱ. Discovery of three species of the genus Neopsylla in Tibet for the first time
    BA Sang, DENGZENG Duo-jie, WEN Xiang-bing, MA Bing-cheng, YANG Xiao-dong, XU Xiang, LI Chun-fu, LI Chun-min, ZHOU Hong-ning, GONG Zheng-da
    Chines Journal of Vector Biology and Control. 2020, 31(3): 335-339. https://doi.org/10.11853/j.issn.1003.8280.2020.03.018
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    Objective To investigate the fauna and distribution of fleas in the southeast of Tibet autonomous region (Tibet), and to provide a basis for further research on flea fauna in the region. Methods With Linzhi in the southeast of Tibet as the research area, small mammals and their parasitic fleas in the farming areas with different altitudes were selected as the research objects. A large rat trap was used for the investigation and sampling of small mammals, their parasitic fleas were collected, and the specimens were classified and identified in the laboratory. Results A batch of flea specimens of Neopsylla Wagner, 1903, were collected, and among them, N. hongyangensis Li, Bai et Chen, 1986, N. specialis schismatosa (Li, 1980) and N. biseta Li et Hsieh, 1964 were discovered for the first time in Tibet and were the new records of local species. This article describes and reports these three species in terms of the main identifying characteristics, distribution areas, host animals, and the structure of female and male terminalia drawn based on the voucher specimens. In addition, this article discusses the problems in the geographical distribution and classification of fleas. Conclusion Up to now, a total of 8 species (subspecies) of Neopsylla have been discovered in Tibet.
    • Investigation
  • An analysis of surveillance results of plague in Yuxi, Yunnan province, China, 1985-2018
    ZHAO Qiu-fang, ZUO Shun-wu, YANG Ru-song, NI Zhao-lin, ZENG Li-ping, LIU Hong-yan, NONG Lu-ming, WU Qiang
    Chines Journal of Vector Biology and Control. 2020, 31(3): 340-344. https://doi.org/10.11853/j.issn.1003.8280.2020.03.019
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    Objective To analyze the changes in the species and densities of the hosts and vectors of plague in Yuxi, Yunnan province, China, with understanding its epidemic pattern, and to provide scientific evidence for preventing and controlling plague. Methods According to the National Plague Surveillance Protocol and Yunnan Provincial Plague Surveillance Protocol, we collected the surveillance data of the hosts, vectors, pathogeny, and serology from seven counties and two districts of Yuxi from 1985 to 2018. We calculated the densities of plague hosts, rate of flea infestation, and flea index by Excel 2010 software, and estimated the Pearson correlation coefficient between Rattus tanezumi density and Xenopsylla cheopis by R3.5.1 software. Results There were two human plague outbreaks in Yuxi, 1985-2018, involving 11 confirmed cases of bubonic plague (9 cases in Yuanjiang county and 2 cases in Xinping county). A total of 59 331 myomorphous rodents were captured, involving 21 species of 13 genera of 6 families of 3 orders, and the overall capture rate was 3.78% (95% confidence interval:3.75%-3.81%). The dominant species was R. norvegicus, accounting for 57.80% of the total number. A total of 55 137 parasitic fleas were collected, involving 8 species of 8 genera of 5 subfamilies of 4 families. The rate of flea infestation was 28.36%, and the overall flea index was 0.83. The dominant species was X. cheopis, accounting for 46.32% of the total number. Indirect hemagglutination assay detected 11 positive serum samples out of 35 412 samples from host animals, and yielded 100% positive results for 11 serum samples of suspected plague patients. Reverse indirect hemagglutination assay detected 4 out of 7 organ samples from rodent. Four strains of Yersinia pestis were isolated from 89 968 host animals examined, and the test was negative for all 33 028 fleas examined. There was no significant association of R. tanezumi density and X. cheopis (r=-0.09, P=0.658). Conclusion During the recent twenty years, the species and densities of plague hosts and vectors were kept at relatively stable levels, and plague was in a relatively silent period in its epidemic foci. However, the main host R. tanezumi and the main vector X. cheopis are still maintained in a certain number, demanding strengthened plague surveillance and improved surveillance quality for timely detection and prevention of the occurrence and spread of human plague.
  • An analysis of surveillance results of plague in Tibet autonomous region, China, 2014-2018
    MA Zhan-jun, ZHA Xi, CHEN Zi-qiang, BASANG Ze-ren
    Chines Journal of Vector Biology and Control. 2020, 31(3): 345-349. https://doi.org/10.11853/j.issn.1003.8280.2020.03.020
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    Objective To evaluate the plague epidemic situation by analyzing the plague surveillance data of the natural plague focus of Marmot himalayan in Tibet autonomous region(Tibet), China, from 2014 to 2018, and to provide a basis for scientific prevention and control of plague in this area. Methods Based on the data of 52 plague natural foci and counties in Lhasa, Shigatse, Shannan, Linzhi, Changdu, Naqu, and Ali during 2014-2018, the database was established by Excel 2003 software, and the data were statistically analyzed by SPSS 17.0 software. Small mice and vector fleas were described by composition ratio, the difference of positive detection rate of Yersinia pestis between different cities (prefectures) was tested by χ2 test. Regression and correlation analysis on the relationship between the number of Y. pestis and marmot density. Results No human plague was reported in Tibet from 2014 to 2018. The surveillance results of animal plague showed that the density of Himalayan marmots (main hosts of plague) was 0.02-0.06 inds/hm2. There was a year-by-year decreasing trend in marmot density distribution over time. The capture rate of small-sized rodents was 1.00%, with Ochotona curzoniae as the dominant species, accounting for 74.88%. Callopsylla dolabris and Oropsylla silantiewi were dominant species in vector fleas. The body flea infestation rate of marmots was 27.84%, with a flea index of 0.52.The burrow flea infestation rate was 0.77%, with a flea index of 0.01. A total of 2 526 animal samples distributed in 6 cities (prefectures) and 21 counties (districts) were tested and 106 strains of Y. pestis were isolated with the positive rate was 4.20%. There was a significant difference in the positive rate of Y. pestis among the cities (prefectures) (χ2=293.646, P<0.001). Among them, Ali was the highest, accounting for 37.14%, and followed by Lhasa, accounting for 10.79%. A total of 29 668 animal serum samples were tested, with 50 samples (39 from wild dogs and 11 from Tibetan sheep) having positive results (positive rate:0.17%), which were distributed in 13 counties/districts in 4 cities/prefectures, especially in Lhasa which contributed the most to the number (27 samples). The number of Y. pestis detected changed linearly with the density of marmot (F=10.751, P=0.046), with a positive correlation (r=0.884, P=0.023). Conclusion No human plague occurred in Tibet from 2014 to 2018. Although animal plague shows a downward trend, it is still prevalent. Due to the grim plague situation, plague surveillance should be strengthened, and integrated and long-term prevention and control measures should be taken, especially in key cities with active epizoonotic situation.
  • An analysis of surveillance results of brucellosis in Jiaojiang district, Taizhou, Zhejiang province, China, 2011-2018
    GUAN Chang-hui, WANG Ji-shun, YANG Nian-zhong
    Chines Journal of Vector Biology and Control. 2020, 31(3): 350-352. https://doi.org/10.11853/j.issn.1003.8280.2020.03.021
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    Objective To explore the prevalence and related risk factors of brucellosis in Jiaojiang district, Taizhou, Zhejiang province, China. Methods From 2011 to 2018, sampling was performed in Jiaojiang district in proportion to its population, and serological tests were performed for the high-risk population of brucellosis. The Rose Bengal plate test was used for initial screening, and the diagnosis of positive patients was confirmed by the tube agglutination test. The chi-square test was used to compare the positive rates of Brucella antibodies in the subjects with different monitoring years, sexes, ages, years of exposure, and types of work and in different regions. Results A total of 275 people were monitored, and 15 (5.45%) tested positive for Brucella antibodies. Cattle raising was a risk factor for brucellosis (χ2=12.744, P=0.013). The workers with a service length of 5-10 years had the highest antibody-positive rate (13.89%). A total of 9 147 dairy cows were monitored, and 167 (1.83%) of which tested positive for Brucella antibodies. Conclusion Brucella infection persists in Jiaojiang district, so it is necessary to strengthen the training and promotion of brucellosis prevention and control knowledge for the high-risk population, improve their self-protection awareness, and protect them when raising livestock and processing beef and mutton to reduce the infection rate of brucellosis in this area.
  • An investigation of inapparent infections in a local outbreak of dengue fever in an island area of Zhejiang province, China
    YE Ling, TAN Qi-long, ZHAO Jian-gang, LI Shi-bo, REN Yi, GUAN Lin-fu, SHU Ji-wei
    Chines Journal of Vector Biology and Control. 2020, 31(3): 353-357. https://doi.org/10.11853/j.issn.1003.8280.2020.03.022
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    Objective To investigate the inapparent infection status in the population in a local outbreak of dengue fever in an island area of Zhejiang province, China, and to provide a scientific basis for determining the size of the epidemic. Methods Sera were collected from asymptomatic individuals in the epidemic area to detect the anti-dengue immunoglobulin M (IgM), and a descriptive statistical analysis was performed on the detection results. Results The first dengue case in Daishan county was reported in JN island on August 30, 2019. A total of 9 cases were reported in this outbreak, all of which were indigenous infections. From August 31 to September 5, 2019, Daishan County Center for Disease Control and Prevention collected 326 serum samples from the asymptomatic population in batches. The inapparent infection rate of the investigated population was 4.91%, and there was no significant difference between males and females (χ2=1.215, P=0.270). The inapparent infection rate in male population was 4.00%, with a significant difference between different age groups (P=0.021). The inapparent infection rate in female population was 6.80%, with no significant difference between different age groups (P=0.127). There was a significant difference in inapparent infection rate between the unemployed group and other occupational groups (χ2=12.240, P<0.001). The positional distribution of dengue cases and inapparently infected individuals was relatively limited within a range of 50 m radius, with high population density, poor sanitary environment, and high mosquito vector density. There had never been an outbreak of dengue fever in the local history, so it can be determined that all positive IgM individuals were caused by primary infection in this outbreak. Conclusion In an outbreak of dengue fever, inapparent infected individuals are more difficult to find out because they are asymptomatic. The number of infected individuals is actually far more than that of patients, which may be an even more important source of infection.
  • Aggregation tendency and goodness of fit to negative binomial distribution of Oncomelania hupensis in the snail-obtainable soil of a waterway network
    TIAN Jian-guo, LI Gui-fu, LI Jun, HAN Rong-rong, PENG Li-xia
    Chines Journal of Vector Biology and Control. 2020, 31(3): 358-361. https://doi.org/10.11853/j.issn.1003.8280.2020.03.023
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    Objective To investigate the distribution of Oncomelania hupensis in the snail-obtainable soil of a waterway network, and the theoretical guide to finding and killing snails was provided. Methods Twenty soil samples were taken using systematic sampling and environmental sampling methods from three plots of snail-obtainable regions within Xingbang village, Liantang town, Qingpu district, Shanghai, China, in May 2016. Oncomelania hupensis snails on the surface of the soil were picked up and counted; then three pieces of specimens (500.0 g per piece) were taken from each soil sample, and the snails in the soil specimens were collected for counting after being washed with a double-layer sieve. The Kolmogorov-Smirnov D test was used to perform normal distribution analysis for the snails in the soil. Statistical parameters of aggregation tendency were used to describe the snail distribution. The Wilcoxon rank-sum test was used to compare the mean number of the snails among the three plots. The goodness-of-fit test was used to determine whether the snail counts follow a negative binomial distribution. Results Sixty pieces of soil specimens were taken from three plots of Zhujiadai River, Qingsonggang, and Duantoubang in Xingbang village, and they were washed for collecting adult snails in the soil. The Kolmogorov-Smirnov D test showed that the numbers of the snails were not consistent with normal distribution (skewness coefficient=1.03, kurtosis coefficient=0.71, D=0.167, P<0.001). The Wilcoxon rank-sum test showed no significant difference in the snail count between the three plots (Z=0.405, P=0.815). The mean of the snail counts was greater than the median in each plot, and the kurtosis and skewness coefficients both deviated from 0, indicating that the snail counts followed a positively skewed distribution. The variance was greater than the mean, representing an aggregation distribution; the goodness-of-fit test showed that the snail counts fitted a negative binomial distribution (χ2=1.844, P=0.765). Conclusion The distribution of O. hupensis in the soil is consistent with that on the soil of the snail-obtainable regions, which is clustered and positively skewed, following a negative binomial distribution rather than a normal distribution.
  • An investigation of resistance of Culex pipiens quinquefasciatus to common insecticides in Shenzhen, Guangdong province, China
    LIU Yang, ZHANG Shao-hua, QIN Yan-min, LIANG Zhuo-nan, LIN Liang-qiang, LI Jian-feng
    Chines Journal of Vector Biology and Control. 2020, 31(3): 362-365. https://doi.org/10.11853/j.issn.1003.8280.2020.03.024
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    Objective To investigate the resistance of Culex pipiens quinquefasciatus to common insecticides in the urban area of Shenzhen, Guangdong province, China, and to provide a scientific basis for selection of insecticides. Methods Tested Cx. pipiens quinquefasciatus mosquitoes were collected from one residential area in each of the five Shenzhen's municipal districts in 2018. The sensitive baseline method of the larval dipping method was used for resistance tests. In each test group, 5 to 7 insecticide concentrations were set, and 20 larvae were selected for each concentration. The number of dead larvae at different concentrations of insecticides was observed. SPSS 19.0 software was used to calculate median lethal dose (LC50) and its 95% confidence interval, and establish the toxicity regression equation. Results The LC50 of permethrin ranged from 0.148 8 to 4.456 1 mg/L, and the resistance ratio was 14.44 to 432.63. The LC50 of deltamethrin ranged from 0.019 1 to 0.217 6 mg/L, and the resistance ratio was 41.25 to 469.98. The LC50 of efficient cypermethrin ranged from 0.028 7 to 0.212 5 mg/L, and the resistance ratio was 35.67 to 264.14. The LC50 of fenthion ranged from 0.016 7 to 0.055 9 mg/L, and the resistance ratio was 2.26 to 7.55. The LC50 of temephos ranged from 0.000 5 to 0.002 6 mg/L, and the resistance ratio was 1.76 to 9.13. The LC50 of propoxur ranged from 0.254 9 to 4.662 3 mg/L, and the resistance ratio was 1.25 to 22.85. Conclusion Culex pipiens quinquefasciatus in Shenzhen has developed high resistance to many pyrethroids, yet they remain susceptible and non-resistant to organophosphate and carbamate insecticides. To delay the development of insecticide resistance, it is necessary to select appropriate insecticides based on resistance monitoring results and take proper rotation treatments.
  • An investigation of mosquito infestation in the underground garages of residential areas in Jiaxing, Zhejiang province, China and a discussion on the countermeasures
    LI Yue-feng, QI Yun-peng, FU Xiao-fei, HOU Zhi-gang
    Chines Journal of Vector Biology and Control. 2020, 31(3): 366-369. https://doi.org/10.11853/j.issn.1003.8280.2020.03.025
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    Objective To explore the status of mosquito infestation in the underground garages of residential areas in Jiaxing, Zhejiang province, China, and to analyze the causes and suitable countermeasures. Methods The mosquito trap lamp and mosquito-oviposition trap were used to monitor mosquitoes in the underground garages of residential areas from April 2017 to March 2018, and the mosquito breeding sites in the garages were also investigated. The differences of mosquito density and mosquito ovitrap index (MOI) in garages of different sizes and types of enclosures were compared by Kruskal-Waillis test with multiple independent samples and Mann-Whitney U test with two independent samples, respectively. Results A total of 12 583 mosquitoes were captured in 68 underground garages, of which 82.40% (10 368/12 583) were females and 17.60% (2 215/12 583) were males. Culex pipiens pallens and Cx. pipiens quinquefasciatus were the dominant species, accounting for 65.25% (8 210/12 583) and 33.93% (4 270/12 583), respectively. The seasonal fluctuation of overall mosquito density showed a unimodal trend, reaching its peak in August. Medium and small garages had a significantly higher overall mosquito density than ultra-large and large garages (χ2=66.999, P<0.001). Semi-buried garages had a significantly higher mosquito density than fully buried garages (Z=-8.185, P<0.001). There was no significant difference in MOI between garages of different sizes (χ2=2.158, P=0.381). Semi-buried garages had a significantly higher MOI than fully buried garages (Z=4.007, P=0.001). The positive mosquito infestation garages accounted for 79.41% (54/68) of the total survey, and the positive rate of breeding sites was 23.36% (64/274). Conclusion Mosquito breeding and infestation in the underground garages of residential areas in Jiaxing were obvious, which should be concerned by relevant departments. In terms of prevention and control measures, it is necessary to focus on controlling mosquito breeding sites in underground garages, and to establish a long-term prevention and control mechanism.
  • Results and analysis of mosquito density monitoring in three districts of Yinchuan, Ningxia, China, 2016-2018
    HU Ming-ming, ZHENG Yan-juan, WU Jian-hua, TAN Yu-zhen
    Chines Journal of Vector Biology and Control. 2020, 31(3): 370-372. https://doi.org/10.11853/j.issn.1003.8280.2020.03.026
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    Objective To comprehensively grasp and analyze the mosquito density and its seasonal fluctuation in Xingqing, Xixia, and Jinfeng districts of Yinchuan, Ningxia Hui autonomous region, China, to provide a scientific basis for the formulation of effective prevention and control programs for vector-borne diseases such as Japanese encephalitis. Methods In accordance with the requirements of the Ningxia Vector Surveillance Implementation Protocol, the lamp trapping method was used to monitor the mosquito density in Xingqing, Xixia, and Jinfeng districts of Yinchuan from May to September of each year from 2016 to 2018, and the surveillance data were collected and analyzed. Results In 2016-2018, a total of 11 690 mosquitoes were captured in the three districts of Yinchuan, with a mean mosquito density of 15.06 mosquitoes/light·night, which belonged to 3 species, 2 genera, i.e., Culex pipiens pallens, Anopheles sinensis, and Cx. tritaeniorhynchus. Culex pipiens pallens accounted for 87.01% of the total number of adult mosquitoes captured, and was the dominant species. The mosquito density in the three districts were as follows:Jinfeng district > Xixia district > Xingqing district. The mosquito density in different habitats was as follows:livestock areas > rural houses > parks > hospitals > urban residential areas. According to the monthly density analysis from 2016 to 2018, the mosquito density peaked in July and August. The species composition of mosquitoes varied from year to year (χ2=570.738, P<0.001). Conclusion The local mosquito characteristics implies the necessary to increase the surveillance efforts for facilitating better mosquito control program in Yinchuan, China.
  • An analysis of the rodent surveillance results in Xi'an, China, 2015-2018
    LI Guang-shuai, PANG Song-tao, LEI Xiao-gang, XUE Wei, CHEN Bao-zhong
    Chines Journal of Vector Biology and Control. 2020, 31(3): 373-375. https://doi.org/10.11853/j.issn.1003.8280.2020.03.027
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    Objective To investigate the species composition, density, and seasonal variation of rodents in Xi'an, China, and to provide a scientific basis for formulation of rodent control and deratization measures. Methods Five rodent surveillance sites were selected from urban residential areas, natural villages, and the catering industry in each of the four districts/counties selected according to their geographical location (east, south, west, and north) in Xi'an. Surveillance was performed in the middle of each odd month using the trap-at-night method (i.e., traps were laid at night and recovered at day start). The rodent species were identified, and chi-square test was used for statistical analysis of the species composition of rodents in the four years and in different habitats. Results A total of 397 rodents belonging to 4 species of rodents were captured. The mean rodent density was 0.42% capture rate, lowest in 2016 (0.27%) and highest in 2018 (0.58%). Mus musculus was the dominant species, accounting for 52.90%. The rodent density had an unapparently bimodal seasonal variation, with a minor peak observed in January (0.47%), a major peak in July (0.48%), and a trough in November (0.34%). The rodent density was highest in natural villages (1.08%) and lowest in urban residential areas (0.24%). The dominant rodent species in different habitats was M. musculus, with significant differences in the species composition of rodents (χ2=60.875, P<0.001). The seasonal variation of rodent density was stable in urban residential areas, bimodal in natural villages, and unimodal in the catering industry. Mus musculus showed a clear seasonal variation among different rodent species, with a peak observed in January and July. Conclusion From 2015 to 2018, the mean density of rodents in Xi'an showed an upward trend. The density, species, and seasonal variation of rodents differ in different years and habitats. It is suggested that measures for rodent control and deratization in different habitats should be formulated, with rural areas as the focus of the work, to reduce rodent-borne diseases risk.
    • Review
  • Research progress in dengue virus detection in Aedes albopictus
    WANG Jin-na, HOU Juan, LIU Qin-mei, WU Yu-yan, LI Tian-qi, GONG Zhen-yu
    Chines Journal of Vector Biology and Control. 2020, 31(3): 376-379. https://doi.org/10.11853/j.issn.1003.8280.2020.03.028
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    Aedes albopictus is the main vector of dengue virus in China. The transmission modes of dengue virus in mosquitoes are mainly blood-sucking transmission and vertical transmission. The susceptibility of Ae. albopictus to dengue virus is mainly related to viral titer, viral serotype, meteorological factors, symptoms of infected individuals, and the influence of symbiotic bacteria in Ae. albopictus. The detection of dengue virus in Ae. albopictus specimens can be affected by the methods of collection, transportation, and storage. This paper mainly reviews the detection of dengue virus in Ae. albopictus from the aspects of infection mechanism, common detection methods, susceptibility, and possible influencing factors, so as to provide a reference for dengue vector surveillance and control.
  • Research progress in MinION sequencing technology and its application
    YAN Dong-ming, ZHAO Ning, ZHAO Chun-chun, WANG Jun, SONG Xiu-ping, ZHU Cai-ying, LIU Qi-yong, ZHANG Qin-feng
    Chines Journal of Vector Biology and Control. 2020, 31(3): 380-384. https://doi.org/10.11853/j.issn.1003.8280.2020.03.029
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    In 2014, the nanopore sequencer MinION was released by Oxford Nanopore Technologies (ONT), representing the birth of a novel sequencing technology. The device is extremely portable and can carry out target detection in the field through a laptop. It is characterized by single-molecule sequencing, real-time monitoring of sequencing data, ultra-long read lengths, and low cost. It has been applied to the identification of microbial populations, whole genome sequencing, discovery of new species, etc. Although the technology has made impressive achievements in recent years, there are also some problems and challenges. This review mainly summarizes the technical characteristics and development fields of the MinION sequencer, and discusses its development prospects.
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