20 June 2021, Volume 32 Issue 3
    

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    Expert Forum
  • Research progress in epidemic situation and control techniques of tick-borne diseases in pets
    WEI Na-na, ZHANG Hou-shuang, ZHOU Jin-lin
    Chines Journal of Vector Biology and Control. 2021, 32(3): 257-264. https://doi.org/10.11853/j.issn.1003.8280.2021.03.001
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    Ticks are obligate hematophagous ectoparasites, and also are the vectors of many pathogenic viruses, bacteria, fungi, and protozoa infecting human and animals, which are of great significance to the public health. In recent years, the number of pets has increased dramatically, leading to the increasing incidence of tick-borne zoonoses via pets. This article reviews the common parasitic ticks in pets and their characteristics, common tick-borne pathogens infecting pets, the epidemic situation of common tick-borne diseases in pets, and the research progress in prevention and control techniques, with the hope of providing a reference for the integrated prevention and control of tick-borne diseases in pets.
    • Experimental Study
  • A genetic structure analysis of mtDNA COⅠ gene sequence of Anopheles sinensis populations in Yunnan province, China
    ZENG Xu-can, XU Xiang, YANG Rui, WEI Chun, WU Lin-bo, LUO Chun-hai, SUN Xiao-dong
    Chines Journal of Vector Biology and Control. 2021, 32(3): 265-270. https://doi.org/10.11853/j.issn.1003.8280.2021.03.002
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    Objective To explore the genetic variation and population structure of Anopheles sinensis by analyzing the mitochondrial cytochrome c oxidase subunitⅠ(mtDNA COⅠ) gene of An. sinensis in Yunnan province, China. Methods From 2018 to 2019, mosquito trap lamps (Gongfu Xiaoshuai) were used to collect mosquitoes in six sampling sites, namely, Suijiang, Mengla, Tengchong, Luoping, Yuanjiang, and Funing. After the mosquitoes were identified as An. sinensis via morphology and molecular biology, the mitochondrial COⅠ gene was amplified and sequenced. MEGA 6 software was used to analyze the sequencing results, and DnaSP5 software was used to calculate the polymorphism-related indices and perform the mismatch analysis of An. sinensis populations from various areas. Arlequin 3.5.2.2 software was used to perform the analysis of molecular variance and neutrality tests and calculate the genetic differentiation (FST values) and the number of migrants (Nm values). Results In this study, 210 samples were successfully amplified from 6 An. sinensis populations (from six sampling sites) and there were 96 haplotypes. The haplotype diversity was 0.97 and nucleotide diversity was 0.011; the intra-population variation rate was 90.80% and the inter-population variation rate was 9.20%. Suijiang and Luoping had the highest FST value (0.21) and the lowest Nm (0.96). Apart from Tengchong, the Tajima's D values in other places were negative, and the P values were all greater than 0.05. The mismatch analysis showed that the curve had two peaks. Conclusion There is abundant genetic diversity among An. sinensis populations in Yunnan province and the rate of intra-population variation is greater than that of inter-population variation. Genetic differentiation is observed in Suijiang and Luoping, with no genetic differentiation observed in other areas. There is no population expansion of An. sinensis in Yunnan province recently.
    • Vector Surveillance
  • Quality evaluation of vector bionomic surveillance at municipal and county levels in Hebei province, China
    MA Li-hua, HAN Xiao-li, GAO Wen, ZHAO Yong, SONG Ji-wen
    Chines Journal of Vector Biology and Control. 2021, 32(3): 271-275. https://doi.org/10.11853/j.issn.1003.8280.2021.03.003
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    Objective To evaluate vector surveillance at municipal and county levels in Hebei province, China, and to find out quality problems in the surveillance work to guide the improvement of surveillance work and its quality in Hebei province. Methods The vector surveillance specimens from 57 municipal and county quality control points were checked, and the compliance rate of surveillance data was calculated. The scores of 8 quality evaluation indicators of each quality control point were quantified, and the t-test, Mann-Whitney U test, and Friedman Q-test were used to analyze the compliance level of monitoring. Results In Hebei province, the mean compliance rate of rodent surveillance data was (80.95±40.07)% at the municipal level and (78.06±28.50)% at the county level. For mosquito surveillance data, the mean compliance rate was (77.84±27.76)% at the municipal level and (83.03±26.09)% at the county level. For fly surveillance data, the mean compliance rate was (84.27±11.67)% at the municipal level and (73.75±25.93)% at the county level. For cockroach surveillance data, the mean compliance rate was (95.59±8.53)% at the municipal level and (85.99±18.03)% at the county level. There were no significant differences in the compliance rates of the surveillance data of four vectors between the municipal level and county level (P>0.05). All 8 indicators reached the level of "relatively good" or higher at the municipal level, and 7 indicators at the county level. Both municipal and county quality control points had high scores in 4 indicators-the completion rate of surveillance points, the stability of surveillance personnel, the timeliness of reports, and the compliance rate of surveillance tools. The indicators to be improved for the municipal level were the standardization of report filling (3.09±0.80 points), the compliance rate of surveillance habitats (3.32±0.81 points), the compliance rate of surveillance data (3.46±1.06 points), and the compliance rate of surveillance time (3.64±0.98 points). The indicators to be improved for the county level were the compliance rate of surveillance data (2.94±1.79 points), the standardization of report filling (3.11±1.00 points), the compliance rate of surveillance habitats (3.30±1.32 points), and the compliance rate of surveillance time (3.46±1.11 points). Conclusion The overall quality of vector surveillance is good both at municipal and county levels in Hebei province, but quality control points at the same level show mixed surveillance qualities. Both municipal and county points should make up for the weak links to improve surveillance quality.
  • Seasonal distribution of Meriones unguiculatus nest fleas in Kangbao pasture, a natural plague focus of Hebei province, China
    KANG Dong-mei, NIU Yan-fen, YAN Dong, LIU Guan-chun, CUI Yao-ren, DU Guo-yi, LAN Xiao-yu, HOU Zhi-lin, REN Xing-yu, YAN Ping, MENG Feng-xia
    Chines Journal of Vector Biology and Control. 2021, 32(3): 276-281. https://doi.org/10.11853/j.issn.1003.8280.2021.03.004
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    Objective To analyze the number and composition of Meriones unguiculatus nest fleas in Kangbao pasture, a natural plague focus in Hebei province, China, 2016-2019, to study the changes in the number of M. unguiculatus nest fleas, and to explore a statistical method for analyzing the seasonal distribution of plague vector fleas. Methods Based on the average flea index of M. unguiculatus nest fleas in different months of 2016-2019, the seasonal distribution of the nest fleas was analyzed by the concentration degree method and circular distribution method. The Watson-Williams test was used for hypothesis testing. Results A total of 138 M. unguiculatus nests were detected, in which 35 nests (25.36%) were infested by fleas. In total, 317 fleas were collected, involving 5 species of 4 genera of 3 families. The average flea index was 2.30. Through the year, the number of fleas collected was largest in July, second largest in October, and then in September. Neopsylla bidentatiformis, Nosopsyllus laeviceps kuzenkovi, and N. abagaitui showed double peaks, while Frontopsylla luculenta and Citellophilus tesquorurn mongolicus showed a single peak. According to the concentration degree analysis, the M value was 0.5-0.7 in 2016 and 2017, >0.9 in 2018, and 0.7-0.9 in 2019. The circular distribution analysis found that there was no angular mean in 2016; there were angular means in 2017-2019, but the means were not equal (F=3 714.353, P<0.05). For 2017 and 2019, the mean angle existed, and a=115.76° (r=0.535, Z=21.007, P<0.001); the increase of the number of M. unguiculatus nest fleas peaked on April 27-28, with the peak period during February 20 to July 1. For 2018, the mean angle existed, and a=167.24° (r=0.995, Z=6.806, P<0.001); the peak point of the increase was on June 18-19, and the peak period was from June 8 to June 30. Conclusion The concentration degree method and circular distribution method show that the change in the number of M. unguiculatus nest fleas is seasonal, with the peak point at the beginning of summer and the peak period during spring and summer, which is consistent with the seasonal fluctuation curve. Both methods can be used to study the seasonal fluctuation of fleas. The concentration degree is suitable for data exploration, and the circular distribution method is suitable for determination of peak point and peak period.
  • An analysis of mosquito bionomic monitoring results in the Yellow River irrigation area of Ningxia Hui autonomous region, China, 2019
    LI Hai-jun, HAN Jia, ZHANG Zheng
    Chines Journal of Vector Biology and Control. 2021, 32(3): 282-285. https://doi.org/10.11853/j.issn.1003.8280.2021.03.005
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    Objective To analyze the species composition, distribution, density, and seasonality of mosquitoes in four counties (cities) of the Yellow River irrigation area of Ningxia Hui autonomous region (Ningxia), China, in 2019, and to provide a scientific basis for the prevention and control of mosquitoes and mosquito-borne diseases. Methods The light trapping method was used to carry out mosquito vector monitoring in the urban residential areas, rural houses, livestock sheds, and other habitats of Helan county, Pingluo county, Qingtongxia city, and Zhongning county in the Yellow River irrigation area twice a month during June to September in 2019. Excel 2007 software was used to establish a database, and SPSS 23.0 software was used for statistical analysis of data. The mosquito composition ratio was compared by the chi-square test, and the mosquito density was compared by analysis of variance. Results A total of 34 670 adult mosquitoes were caught from June to September 2019, with an average density of 46.10 mosquitoes/light-trap·night; there was no significant difference in mosquito density between different areas (F=2.357, P=0.930); Helan county had the highest average mosquito density, which was 252.96 mosquitoes/light-trap night. There was a significant difference in the composition of mosquito species between different areas (χ2=3 826.933, P<0.001); the majority of the mosquitoes caught belonged to Culex pipiens pallens and Cx. tritaeniorhynchus, accounting for 55.90% and 43.86%, of the total number of catches, respectively. Among the different habitats, livestock sheds had the highest density of mosquitoes, which was 73.55 mosquitoes/light-tarp·night, and there was a significant difference in the density of mosquitoes between different habitats (F=433.600, P <0.001). The seasonal fluctuation curve of mosquito density showed an obvious single-peak curve, and the difference of mosquito density in different months was statistically significant (F=938.159, P<0.001). Conclusion The mosquito density in the Yellow River irrigation area is generally at a relatively high level. Cx. pipiens pallens and Cx. tritaeniorhynchus are the dominant mosquito species in the area, and livestock sheds and rural houses are the places with a high incidence of mosquito infestation.
  • An analysis of lag effects of meteorological factors on Aedes density indices in Baoshan district, Shanghai, China
    YANG Ying-yu, WANG Ying-ying, CHEN Yun, FU Chao-wei
    Chines Journal of Vector Biology and Control. 2021, 32(3): 286-290. https://doi.org/10.11853/j.issn.1003.8280.2021.03.006
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    Objective To investigate the lag effects of meteorological factors on the density indices of Aedes mosquitoes in Baoshan district, Shanghai, China, and to provide a basis for early warning and prediction for local dengue fever epidemic. Methods A distributed lag non-linear model was used to analyze the lag effects of meteorological factors on Aedes density indices in Baoshan district from April to October, 2019, including daily average temperature, daily minimum temperature, daily maximum temperature, daily average air pressure, daily average wind speed, daily average relative humidity, and daily cumulative rainfall. Results For the net trap index, the lag effect peaked at shorter lags of 0 to 2 days when daily minimum temperature was high, and at longer lags of 20 to 30 days when the temperature was low. For the landing index, the lag effect peaked at shorter lags of 0 to 5 days when daily average temperature was high, and at longer lags of 25 to 30 days when the temperature was low. For the Breteau index, the lag effect peaked at the beginning when daily average temperature was high, and at lags of 5 to 10 days when the temperature was low. For the mosquito ovitrap index, the lag effect peaked at shorter lags of 0 to 3 days when daily average temperature was high, and at longer lags of 15 to 30 days when the temperature was low. Conclusion Meteorological factors, including daily average temperature, daily average relative humidity, and daily average wind speed, have lag effects on the density of Aedes mosquitoes in Baoshan district of Shanghai. High temperature and high humidity, with low or high wind speed, can accelerate the peak of the lag effect on Aedes density. Meteorological changes can be used to predict fluctuations in Aedes density.
  • An investigation of the hosts, vectors, and pathogens of scrub typhus in Pinggu natural focus of Beijing, China
    LI Gui-chang, WANG Yu-jiao, MU Qun-zheng, XIA Qing, LI Dong-mei, YUE Yu-juan, LU Liang, ZHAO Ning, LI Wen, SONG Xiu-ping, WANG Jun, WU Hai-xia, LI Xing-zhou, LIU Qi-yong
    Chines Journal of Vector Biology and Control. 2021, 32(3): 291-297. https://doi.org/10.11853/j.issn.1003.8280.2021.03.007
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    Objective To investigate the species of hosts and vectors, seasonal variation, and pathogen genotypes in the natural focus of scrub typhus in Pinggu district of Beijing, China through field investigation and laboratory study, and to provide a basis for the prevention and control of scrub typhus. Methods Rat traps were placed in field every month for one year, and small mammals were captured to collect chigger mites on body surface and analyze the number, species composition, seasonal variation, and spatial distribution of chigger mites. The small mammals were dissected to collect the liver and the spleen and extract DNA from the tissue, and nested PCR amplification was used to detect the 56 kDa protein gene of Orientia tsutsugamushi (Ot). The genotype of Ot was determined by nucleic acid sequence alignment and the positive rate in small mammals was calculated. Results A total of 734 small mammals belonging to 7 species were captured from September 2018 to August 2019, among which Apodemus agrarius and Mus musculus accounted for 65.26% and 30.52%, respectively, and were the dominant species in Pinggu district. Three genotypes of Ot, i.e., Shimokoshi, Kawasaki, and Japan Gilliam, were detected in the liver and spleen of small mammals, among which Shimokoshi and Kawasaki were more common. The positive rate of Ot was 10.90% in small mammals. The positive rate of Ot was 14.86% in M. musculus and 9.30% in A. agrarius, and thus they were the main hosts in Pinggu district. A total of 31 321 chigger mites belonging to 10 species were collected on the body surface of the small mammals, and Leptotrombidium subpalpale, L. linhuaikongense, and L. scutellare accounted for 84.79%, 6.49%, and 3.63%, respectively. The seasonal variation of L. scutellare was generally consistent with that of scrub typhus cases, and thus L. scutellare might be the main vector in this epidemic focus. L. scutellare was only distributed in the mountainous area and the piedmont transitional zone of Pinggu district. Conclusion A. agrarius and M. musculus are the main hosts and L. scutellare is the main vector in the natural focus of scrub typhus in Pinggu district, and there are at least three genotypes of scrub typhus pathogens. This investigation clarifies the basic elements in the natural focus of scrub typhus in Pinggu district and provides a basis for the prevention and control of scrub typhus, but further studies are needed to investigate the vector effect of other species of chigger mites.
  • Type distribution and molecular characteristics of Yersinia enterocolitica in Anhui province, China, 2018-2019
    YUAN Yuan, SUN Yong, CHANG Hong-wei, CHEN Xiao-long, SA Nan, GAO Da-wei, SU Bin
    Chines Journal of Vector Biology and Control. 2021, 32(3): 298-301. https://doi.org/10.11853/j.issn.1003.8280.2021.03.008
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    Objective To investigate the type distribution and molecular characteristics of Yersinia enterocolitica in Anhui province, China, 2018-2019. Methods Different types of samples were collected from patients with diarrhea, animal feces, and food from 2018 to 2019, Y. enterocolitica strains were isolated to perform systematic biochemical identification, serotyping, polymerase chain reaction detection of virulence genes, and molecular typing by pulsed-field gel electrophoresis (PFGE). Results Among 2 186 samples, a total of 97 strains of Y. enterocolitica were isolated, with O:3 (21/97, 21.65%) and O:5 (17/97, 17.53%) being the main serotypes. Virulence gene analysis showed that 19.59% (19/97) of the strains were attachment invasion locus gene-positive (ail+), Yersinia stable toxin A gene-positive (ystA+), Yersinia stable toxin B gene-negative (ystB-), Yersinia adhesin A gene-positive (yadA+), and yop regulon transcriptional activator gene-positive (virF+); 63.92% (62/97) were ail-, ystA-, ystB+, yadA-, and virF-. Molecular typing by PFGE showed ≥ 95.00% similarity between the strains from patients with diarrhea and the strains from the host pigs. Conclusion In Anhui province, most Y. enterocolitica strains isolated from food, environment, and some patients with diarrhea are non-pathogenic. There are pathogenic strains in the host pigs and some patients with diarrhea. Strains isolated from pigs are closely related to human infection. Pigs are the main host of pathogenic strains of Y. enterocolitica.
  • Monitoring and analysis of insecticide resistance of Aedes albopictus in Xingyi and Chishui cities of Guizhou province, China
    WANG Dan, SHI Peng, ZHAO Wen-ping, YAN Ying, ZHOU Jing-zhu, TIAN Zhen-zao, LIANG Wen-qin
    Chines Journal of Vector Biology and Control. 2021, 32(3): 302-306. https://doi.org/10.11853/j.issn.1003.8280.2021.03.009
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    Objective To investigate the current status of resistance to commonly used insecticides in Aedes albopictus in Xingyi and Chishui cities of Guizhou province, China, to explore the killing effect of Bacillus thuringiensis subsp. israelensis on Ae. albopictus larvae in Chishui, and to provide a scientific basis for the prevention and control of Aedes vector and related infectious diseases. Methods In September 2018 and July 2019, Ae. albopictus larvae were collected from small water containers in communities in different locations of Xingyi and Chishui and were reared to obtain the F1 to F2 generations in the laboratory. The larval dipping method and the contact tube method recommended by WHO were used to investigate the insecticide resistance of Ae. albopictus larvae and adults, respectively, and determine the degree of insecticide resistance. Results The resistance ratios of Ae. albopictus larvae against deltamethrin, beta-cypermethrin, permethrin, and DDVP were 44.78, 39.18, 113.74, and 2.74 folds, respectively, in Xingyi city, and 38.38, 24.25, 26.37, and 1.64 folds, respectively, in Chishui city. In addition, the resistance ratios of Ae. albopictus larvae against propoxur and B. thuringiensis subsp. israelensis were 7.51 and 1.28 folds, respectively, in Chishui. The 24-hour mortality rates of adult Ae. albopictus mosquitoes in Xingyi against deltamethrin, beta-cypermethrin, permethrin, and fenitrothion were 27.22%, 57.89%, 46.75%, and 100%, respectively. The 24-hour mortality rates of adult mosquitoes in Chishui against deltamethrin, beta-cypermethrin, and permethrin were 53.00%, 93.33%, and 94.40%, respectively, and the mortality rate against propoxur was 99.20%. Conclusion Ae. albopictus larvae in both cities have developed moderate or above resistance to pyrethroid insecticides and are sensitive to DDVP. Ae. albopictus larvae from Chishui have low resistance to propoxur and are sensitive to B. thuringiensis subsp. israelensis. In both Xingyi and Chishui cities, Ae. albopictus adults have resistance or suspected resistance to pyrethroid insecticides and are sensitive to fenitrothion or propoxur. It is recommended to adhere to the principle of integrated vector management in both cities, timely monitor the level and changing trend of insecticide resistance of Ae. albopictus, suspend the use of high-resistance insecticides, and adopt an appropriate rotation or combination strategy, so as to delay the development of insecticide resistance.
  • Monitoring of the density of the dengue vector Aedes albopictus and its resistance to commonly used insecticides in Zigong of Sichuan province, China
    LI Chun-yan, TIAN Feng-yuan, LING Yuan-nong, XIAO Chong-kun, ZHANG Fu-yan
    Chines Journal of Vector Biology and Control. 2021, 32(3): 307-311. https://doi.org/10.11853/j.issn.1003.8280.2021.03.010
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    Objective To investigate the seasonal variation of the dengue vector Aedes albopictus and its resistance to several commonly used insecticides in Zigong of Sichuan province, China, and to provide a theoretical basis for guiding the selection and application of insecticides and effectively controlling the epidemic situation of dengue fever. Methods Breteau index (BI) and the double mosquito net method were used to monitor the density of Ae. albopictus in Zigong during the peak time of the activity of Ae. albopictus in May to October, 2019. The wild larvae and adults of Ae. albopictus were collected throughout the city using the larval enrichment method and the human-induced adult mosquito sucking method and were reared to the F1 generation in laboratory, and the larva dipping method and the contact tube method recommended by WHO were used to measure the sensitivity of Ae. albopictus larvae and adults to several commonly used insecticides. Excel 2007 and SPSS 19.0 softwares were used to perform the statistical analysis of the monitoring results with the modified Karber's method. Results The peak time of the activity of Ae. albopictus was July to October in Zigong. The mean annual BI was 8.50, and the mean net trap index was 4.50 mosquitoes/net·hour. The density of Ae. albopictus in Zigong showed single-peak curve distribution throughout the year, with the highest density in September, and there was no significant difference in the mean positive rate of Ae. albopictus between different environmental containers (χ2=8.094, P=0.231). The Ae. albopictus larvae showed moderate resistance to beta-cypermethrin, permethrin, and deltamethrin and were sensitive to temephos and dichlorvos, while the adults showed resistance to deltamethrin and suspected resistance to beta-cypermethrin and were sensitive to malathion and propoxur. Conclusion Ae. albopictus in Zigong has relatively high resistance to pyrethroid insecticides and low resistance to organophosphate and carbamate insecticides, and therefore, insecticides should be used reasonably based on local conditions and the above monitoring results to improve control effect.
    • Vector Infectious Disease
  • Impact analysis of dengue fever epidemic in Cambodia and tourism to Cambodia on imported dengue fever in China from 2011 to 2019
    LUN Xin-chang, ZHAO Chun-chun, ZHU Cai-ying, WU Hai-xia, WANG Jun, WANG Zhi-hui, LI Wen-yu, LIU Qi-yong, MENG Feng-xia
    Chines Journal of Vector Biology and Control. 2021, 32(3): 312-317. https://doi.org/10.11853/j.issn.1003.8280.2021.03.011
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    Objective To investigate the epidemic situation of dengue fever in Cambodia, the main source of imported cases to China, and the main influencing factors for imported dengue fever from Cambodia to China, and to help formulate targeted response measures and effectively prevent imported cases from abroad. Methods Dengue fever information in Cambodia from 2011 to 2019 was collected from the official website of the World Health Organization and the official account of Public Health Concerns at Frontier Ports. The information about dengue fever cases imported to China from Cambodia was extracted from the China Information System for Disease Control and Prevention. The number of tourists from China to Cambodia was inquired on the website www.chinaqw.com. Excel 2016 software was used to analyze the trend of dengue fever epidemic in Cambodia, the annual growth rate of the number of tourists from China to Cambodia, and the data on cases of dengue fever imported from Cambodia to China from 2011 to 2019. SPSS 19.0 software was used to perform partial correlation analysis. Results During 2011 to 2019, Cambodia had the highest incidence of dengue fever in 2019. In 2018, the proportion of cases of dengue fever from Cambodia increased sharply among total imported cases in China. In 2019, Cambodia became the main source of China's imported cases. At the same time, the number of Chinese residents visiting Cambodia increased year by year. The partial correlation coefficient between the proportion of dengue fever cases from Cambodia and Cambodia's incidence of dengue fever was 0.880 (P=0.004); the partial correlation coefficient between the proportion of dengue fever cases from Cambodia and the number of tourists to Cambodia was 0.887 (P=0.003). Conclusion The number of cases of dengue fever in Cambodia and the number of tourists from China to Cambodia are important factors affecting the number of imported cases in China. Chinese authorities should pay close attention to the incidence of dengue fever and the number of floating population in neighboring countries with close interactions.
  • Comparison of characteristics of dengue fever epidemic between Ruili and Jinghong, Yunnan province, China, 2006-2018
    XU Ming-fang, YUE Yu-juan, LIU Xiao-bo, WANG Jun, LIU Guo-jun, LIU Qi-yong, ZHANG Qin-feng
    Chines Journal of Vector Biology and Control. 2021, 32(3): 318-323. https://doi.org/10.11853/j.issn.1003.8280.2021.03.012
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    Objective To compare the characteristics of dengue fever epidemic between Ruili and Jinghong in Yunnan province, China, and to provide a basis for the precise prevention and control of dengue fever in the two cities. Methods The information about local and imported cases of dengue fever was collected in Ruili and Jinghong, Yunnan province from 2006 to 2018, and SPSS 22.0 and R 3.6.2 softwares were used for statistical analysis. Results From 2006 to 2018, Ruili reported a total of 3 022 cases of dengue fever, of which 59.13% were imported cases (59.00% were imported from abroad) and 40.87% were local cases. Among 3 923 cases in Jinghong, imported cases accounted for 3.08% (3.01% were imported from abroad), and local cases accounted for 96.92%. The number of imported cases in Ruili was 14.77 times that in Jinghong. The imported cases in both cities were mainly 16 to 45 years old, and mostly from Southeast Asian countries, especially Myanmar. There were statistically significant differences in sex, age, occupation, and the interval from disease onset to diagnosis of either imported or local cases between the two cities (χ2=7.529, 14.169, and 201.686, all P<0.05; χ2=18.342, 43.723, and 557.247, all P<0.001; Mann-Whitney U=75 032.500 and 2 116 735.000, both P<0.001). Conclusion Most of cases of dengue fever are imported in Ruili but local in Jinghong. Authorities of the two cities should strengthen the surveillance of cases of dengue fever, promptly detect, isolate, and treat cases, and take measures to deal with the epidemic in time.

  • Distribution characteristics of plague epidemics in animals in natural plague foci of Hebei province, China
    BAI Xue-wei, CHEN Yong-ming, NIU Yan-fen, WANG Hai-feng, YAN Dong, SHI Xian-ming, DU Guo-yi
    Chines Journal of Vector Biology and Control. 2021, 32(3): 324-328. https://doi.org/10.11853/j.issn.1003.8280.2021.03.013
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    Objective To analyze the epizootic trend of animal plague in the natural plague foci of Hebei province, China, and to provide evidence for formulating the strategies for the prevention and control of plague in Hebei province. Methods The monitoring data of animal plague in the natural plague foci of Hebei province from 1950 to 2019 were analyzed using Excel 2007 and SPSS 19.0 softwares. The number of Yersinia pestis positive animals was described as constituent ratio. The distribution of different groups was compared by the χ2 test. The seasonal distribution of animal plague was analyzed by concentration degree. Results The median interval of plague epizootics in the natural plague foci of Hebei province was 9.5 years. The epizootics had certain seasonality (M=0.387), with a high frequency during October to November and then during April to May. Kangbao pasture (constituent ratio 73.13%) and Zhaoyanghe town (constituent ratio 26.12%) were the main epizootic areas. Meriones unguiculatus (constituent ratio 87.31%) was the main animal involved in the epizootics. The main vectors were Nosopsyllus laeviceps kuzenkovi (constituent ratio 1.49%) and Citellophilus tesquorum mongolicus (constituent ratio 1.49%). Among positive rodents, 92.25% were naturally dead rodents. The number of Y. pestis strains isolated from M. unguiculatus was significantly different between five rounds of plague epizootics (χ2=20.026, P<0.001). The average density of M. unguiculatus was 1.98/hm2, the average flea index of body fleas was 1.12, and the average flea index of nest fleas was 3.19. Conclusion Plague epizootics in the natural plague foci of Hebei province show intermittent and relatively stable characteristics. In order to reduce the risk of animal plague, close attention should be paid to the density and parasitic flea index of M. unguiculatus, and measures should be taken timely to kill rodents and fleas in spring and autumn. At the same time, the searching for naturally dead rodents in historical epizootic areas should be strengthened to discover plague epizootics in time and prevent the spread of plague.
  • Epidemiological characteristics and host animal monitoring of hemorrhagic fever with renal syndrome in Fujian province, China, 2016-2018
    LIU Jing, CHEN Yang, LIN Dai-hua, XIAO Fang-zhen, LIN Wen, WANG Jia-xiong, HAN Teng-wei, LIU Wei-jun
    Chines Journal of Vector Biology and Control. 2021, 32(3): 329-333. https://doi.org/10.11853/j.issn.1003.8280.2021.03.014
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    Objective To investigate the epidemic situation of hemorrhagic fever with renal syndrome (HFRS) and the population distribution and virus-carrying status of host animals in Fujian province, China, from 2016 to 2018, and to provide a scientific basis for formulating feasible prevention and control measures for HFRS. Methods The descriptive epidemiological method was used to perform a statistical analysis of HFRS case data and host monitoring data in Fujian which were reported in Surveillance Information Reporting and Management System in 2016-2018. The ratio was compared by χ2 test. Results A total of 1 184 HFRS cases were reported in Fujian from 2016 to 2018, with a mean annual incidence rate of 1.02/100 000, and there were 2 deaths, resulting in a mortality rate of 0.17%. Most cases were observed in Nanping, Quanzhou, and Sanming cities. The cases were reported all year round, with the peaks in March to May and November to February, and the peak in spring was higher than that in winter. The high-risk population was young men, and the highest incidence rate was observed in men aged 65-70 years and women aged 60-65 years. A total of 12 854 effective cages were set in the surveillance sites of Fujian and 845 rodents were captured, with a mean density of rodents of 6.57%. A total of 845 lung samples were collected, among which 48 were positive, and the 3-year mean virus-carrying rat index was 0.06. Conclusion The incidence rate of HFRS in Fujian province tends to first decrease and then increase from 2016 to 2018, with high rodent density and virus-carrying rate, and there is still a risk of HFRS outbreak. It is recommended to adopt comprehensive prevention and control measures of vaccination and deratization.
    • Early Warning and Forecast
  • Epidemiological characteristics and risk prediction of scrub typhus in Guangdong province, China
    LI Wen, MA De-long, ZHAO Jia-xin, MU Qun-zheng, LI Gui-chang, LIU Xiao-bo, WANG Jun, ZHANG Qin-feng, LIU Qi-yong, LU Liang
    Chines Journal of Vector Biology and Control. 2021, 32(3): 334-338. https://doi.org/10.11853/j.issn.1003.8280.2021.03.015
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    Objective To analyze the epidemiological characteristics and changing trend of scrub typhus cases in Guangdong province, China from 2012 to 2018, to predict the incidence trend, and to provide a scientific basis for evaluating the prevention and control measures of scrub typhus. Methods The data of scrub typhus cases in Guangdong province from 2012 to 2018 were collected. A descriptive epidemiological analysis was conducted. A seasonal autoregressive integrated moving average (ARIMA) time series model was used to establish a forecasting model, which was evaluated by comparing the observed and predicted values in 2019, and the incidence of scrub typhus in Guangdong province in 2020 was predicted using the model. Results A total of 33 490 scrub typhus cases were reported in Guangdong province from 2012 to 2018, with the incidence increasing year by year, and the cases mainly occurred in June to October. The incidence was highest in the 50-60 years group; there were more cases in females than in males, and farmers (65.49%) were the dominant occupation. The ARIMA (1,1,1)(0,1,1)12 model was fitted with the monthly case data; the Bayesian information criterion was 879.36; the residual sequence was white noise sequence according to the Ljung-Box test, and the adjusted R2 value was 0.377. The fitting effect of the model was good. The actual value in 2019 was basically consistent with the predicted value with 95% confidence interval; the model had a good predictive effect. Conclusion The scrub typhus incidence shows an increasing trend year by year in Guangdong province. The main susceptible populations were people aged 50-60 years, females, and farmers. The ARIMA model can be used to predict the changes in scrub typhus cases in Guangdong province well, suggesting that the relevant departments should strengthen the publicity and education of key population and the epidemic prevention and control in the season with high incidence of scrub typhus.

    • Technology and Method
  • Application of two different algorithms in prediction of adult mosquito density in Qingdao, China
    SONG Fu-cheng, WANG Wei, MA Xiao-fang, LI Bing-hui, XUE Jian-jie, LI Xue-kui, JIANG Hong-rong
    Chines Journal of Vector Biology and Control. 2021, 32(3): 339-343. https://doi.org/10.11853/j.issn.1003.8280.2021.03.016
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    Objective To predict the density of adult mosquito in Qingdao, China using multiple linear regression algorithm and gene expression programming algorithm models, and to investigate their feasibility in predicting the density of adult mosquito density. Methods Meteorological data (monthly maximum temperature, monthly minimum temperature, monthly mean temperature, monthly mean humidity, monthly accumulated precipitation, and monthly accumulated precipitation days) and monthly adult mosquito density from March to November, 2016-2019, in Qingdao were collected. Prediction models were built using the above two methods, respectively, with the data from 2016 to 2018 used as the training set and the adult mosquito density data in 2019 used as the test set to validate the prediction performance of the two models. Results The correlation coefficients of the training set and the test set were 0.94 and 0.93, respectively, in the multiple linear regression algorithm model, and were 0.97 and 0.96, respectively, in the gene expression programming algorithm model. Conclusion The two models based on the meteorological data can favorably predict the adult mosquito density in Qingdao, which provides data support for mosquito prevention and control in the future.
  • Development and application of a portable intelligent rodent tele-monitoring system
    HUANG Qing-zhen, JIA Rui-zhong, WANG Xu, TIAN Zhi-bo, ZHU Qing-wei
    Chines Journal of Vector Biology and Control. 2021, 32(3): 344-347. https://doi.org/10.11853/j.issn.1003.8280.2021.03.017
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    Objective In order to overcome the disadvantages of traditional rodent monitoring methods which were labor-intensive, time-consuming, and of low accuracy, this article used a new portable and efficient electronic monitoring system to monitor the rodents in the target areas in real time. Methods In 2016-2017, the convolutional neural network recognition technology based on deep-learning artificial intelligence was used in laboratory to recognize rodent species and analyze and record their activities, habits, and numbers in the target areas. The system box was developed after continuous adjustment and improvement. In the field application test, a categorical data analysis was performed. Results The system had over 95.00% accuracy of rodent recognition, recording, and analysis and about 90.00% counting accuracy in laboratory, which could monitor the rodent activities within 50 m in diameter in real time with clear images. In the field application, the catching rate was significantly higher than that using sticky boards. Conclusion This portable monitoring system/box realizes the intelligent real-time rodent monitoring based on the local area network, which changes the traditional rodent monitoring methods and provides a digital and smart solution of rodent surveillance information.
    • Investigation
  • Research on the establishment of information management system of vector surveillance in large-scale events
    WU Li-qun, ZENG Jing, SHEN Jin, ZHOU Liang-cai, CHEN Xiao-min
    Chines Journal of Vector Biology and Control. 2021, 32(3): 348-354. https://doi.org/10.11853/j.issn.1003.8280.2021.03.018
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    Objective To enhance information construction for vector surveillance in large-scale events, and to improve the quality and utilization of surveillance data. Methods Monitoring indices were established according to national standards of vector density monitoring, and considering the characteristics and requirements of vector surveillance in large-scale events, an information management system for vector surveillance in large-scale events was established based on internet technology. Results The system was composed of a mobile application (APP) port and a server port. The APP port was used for collecting surveillance data on-site, and the server port was used for real-time inquiry of surveillance information, pooled analysis of surveillance data, and report generation. The system was appropriate for vector surveillance by visual observation or instruments and for identifying the sites with vector invasion in large-scale events. The system was successfully used for vector surveillance in relevant places of the 7th CISM Military World Games at least six times form June to October, 2019. Conclusion The system can meet the requirements of vector surveillance in large-scale events and improve surveillance quality and efficiency. This system holds promise for wide application.
  • An investigation of population structure in the Aedes albopictus midgut infected with Wolbachia in Hainan province, China
    LIU Biao, KANG Xun, LIU Lin, ZHAO Xiu-juan, FU Yu-mei, TIAN Guo-zhen, KANG Le, XIA Qian-feng
    Chines Journal of Vector Biology and Control. 2021, 32(3): 355-360. https://doi.org/10.11853/j.issn.1003.8280.2021.03.019
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    Objective To investigate the prevalence, abundance difference, and genetic relationship of Wolbachia in Aedes albopictus population in Hainan province, China, and to provide a basis for the biological control of mosquito-borne infectious diseases. Methods From July to September 2018, eight counties/cities in Hainan province, Lingshui, Ding'an, Haikou, Wenchang, Sanya, Ledong, Tunchang, and Wuzhishan, were selected in this study. After field collection of adult mosquitoes, morphology and cytochrome c oxidase subunit Ⅰ (COⅠ) gene were used to identify the mosquito species; the 16S rRNA V3-V4 hypervariable regions were used to identify the microbial species in their midgut; the chi-square test was used to analyze whether there was a significant difference in Wolbachia abundance in the midgut microbiota of Ae. albopictus between different areas. MEGA 7.0 software was used to analyze the genetic distances between the obtained gene sequences. Results Among the microorganisms in the midgut of Ae. albopictus in Hainan province, Wolbachia accounted for a relatively high proportion in Ding'an county (84.67%), Sanya city (80.34%), Lingshui county (68.77%), and Haikou city (56.89%), and was the dominant species; the infection rates in Ledong county (1.50%) and Wuzhishan city (0.01%) were extremely low. The abundance of Wolbachia in the midgut microbiota was significantly different between different areas (χ2=322.950, P<0.001). The genetic distance analysis suggested that there were exchanges of Wolbachia strains between different areas, and there were some differences in genes between the Wolbachia strains in the same region. Conclusion The midgut of Ae. albopictus has a high infection rate with Wolbachia in Hainan province, but there are low infection rates in Ledong county and Wuzhishan city; there are certain differences in the abundance of Wolbachia in the midgut of Ae. albopictus between different areas; there is genetic diversity among the Wolbachia strains in various areas.
  • An investigation of geographical distribution, host, and seasonality of ticks in Zhengzhou, China
    SHI Jia-jia, LYU Ming-jie, YUAN Zhong-liang
    Chines Journal of Vector Biology and Control. 2021, 32(3): 361-364. https://doi.org/10.11853/j.issn.1003.8280.2021.03.020
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    Objective To investigate the species, number, geographical distribution, host, and seasonal fluctuation of ticks in Zhengzhou, China, and to provide a basis for tick prevention and control. Methods Free-living ticks were collected with the tick drag-flag method in Zhengzhou from January to December in 2019. Host infection by ticks was investigated by capturing ticks from animals' body surface. Data were collected, calculated, and analyzed using Excel 2019 software. Results All the ticks collected from populated and unpopulated rural areas, mountains, and scenic spots in Dengfeng, Xinmi, Gongyi, Xingyang, and Xinzheng cities as well as Zhongmou county were identified as Haemaphysalis longicornis. The average density of free-living ticks was 6.97 ticks/100 m, the average infection rate was 41.18%, and the average number of ticks per host was 2.03. H. longicornis first appeared in April, had the highest density in July, and disappeared in November. Conclusion H. longicornis is mainly distributed in the unpopulated rural areas and scenic spots of Zhengzhou, and tends to spread to the urban areas. The population activity peaks in summer and autumn.
    • Control Experiment
  • Effectiveness evaluation of ‘mosquito-free village’ construction in Qingtian county, Zhejiang province, China
    ZHU Hai-bo, YE Hui-feng, CHEN Ming, ZENG Yong, CHEN Fan, FU Zheng-jun
    Chines Journal of Vector Biology and Control. 2021, 32(3): 365-368. https://doi.org/10.11853/j.issn.1003.8280.2021.03.021
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    Objective To analyze the investment in the construction of ‘mosquito-free village’ in Qingtian county, Zhejiang province, China, and to evaluate the role of ‘mosquito-free village’ in the control of mosquito density, the control of mosquito-borne infectious diseases such as dengue fever, and the promotion of rural development. Methods From April to October in 2017-2019, the pipette method was used to measure the density of larval mosquitoes in Xiaozhoushan village. From April to October in 2017-2018, the double mosquito net method was used to determine the density of adult mosquitoes. In the middle of October in 2017-2019, a questionnaire survey was used to investigate the investment in mosquito control. SPSS 16.0 software was used for data analysis including the t-test and analysis of variance. Results Since the construction of ‘mosquito-free village’ in Xiaozhoushan village, local mosquito density had decreased significantly. The 100-house index fell from 42.7 places/100 houses in 2017 to 2.9 places/100 houses in 2019. The adult mosquito density decreased from 29.3 mosquitoes/net·hour in 2017 to 2.4 mosquitoes/net·hour in 2018. The expenditure of mosquito control had decreased year by year, and the expenditure of mosquito control in 2019 was significantly lower than that in 2017 before the construction of ‘mosquito-free village’. The average investment per household decreased from 35.0 yuan to 5.0 yuan, and the collective investment of the village decreased from 74 000.0 yuan to 17 000.0 yuan. Moreover, the construction of ‘mosquito-free village’ could effectively reduce the possibility of local transmission of dengue fever and thus reduce the cost of response to the epidemic of dengue fever. Conclusion The construction of ‘mosquito-free village’ in rural areas can effectively reduce the density of mosquitoes. It is sustainable and economical. Xiaozhoushan's experience of ‘mosquito-free village’ construction can be promoted in hilly rural areas where small bodies of standing water are the main breeding place of mosquitoes.
  • Development and application of an automatic molluscicide infusing and drip penetration device for Oncomelania hupensis snail control with niclosamide suspension
    MA Yu-cai, WU Hong-chu, LIANG Xiao-tian, LI Chuan-dong, WANG Fu-biao, ZUO Yin-ping, TANG Kai, WANG Jian, DU Guang-lin, WANG Jian, GAO Yang, YANG Hai-tao, SUN Le-ping
    Chines Journal of Vector Biology and Control. 2021, 32(3): 369-373. https://doi.org/10.11853/j.issn.1003.8280.2021.03.022
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    Objective To develop an automatic molluscicide infusing and drip penetration device for snail control with niclosamide suspension, and to provide a novel method for killing Oncomelania hupensis under special conditions. Methods The drip penetration technique, as well as water conveyance boosting and continuous molluscicide infusing, was used to develop an automatic molluscicide infusing and drip penetration device for snail control. The snail control effect and cost of this device were evaluated. Data were gathered by Excel 2016 software, and the Chi-square test was performed by SPSS 16.0 software to determine the mortality and adjusted mortality of O. hupensis. Results The automatic molluscicide infusing and drip penetration device for snail control consisted of four parts:boosting water conveyance, filtration purification, automatic molluscicide infusing, and drip penetration pipe network; the rated power of booster pump was 4 kW, the proof pressure of filter was 800 kPa, and the single-hole flow of drip penetration pipe was 0-2 L/h. In group A (2-meter space between two drip penetration pipes), group B (1-meter space between two drip penetration pipes), and group C (spraying control), the adjusted mortality rates of snails were 67.08%, 75.71%, and 66.22%, respectively, after 7 days of molluscicide application, and there was a significant difference in the adjusted mortality between the three groups (χ2=8.809, P=0.012); the adjusted mortality rates of snails were 75.15%, 79.27%, and 78.34%, respectively, after 15 days of molluscicide application, and there was no significant difference in the adjusted mortality between the three groups (χ2=1.369, P=0.504); the density of live snails decreased by 80.78%, 83.81%, and 80.63%, respectively, after 30 days of molluscicide application. The total cost of an automatic molluscicide infusing and drip penetration device for snail control was 9 805 yuan, of which the mobile equipment accounted for 68.33%, and the fixed drip penetration pipe network accounted for 31.67%. If the service life of the pipe network was set as 10 years, the average cost of the pipe network equipment for snail control per year was 0.16 yuan/m2. Conclusion The automatic molluscicide infusing and drip penetration device for snail control is labor-saving, efficient, and practical. It is advised that the space between two drip penetration pipes should be set as 1 metwer.
  • A study of effectiveness of 5% pyriproxyfen and fenthion granules in controlling mosquito larvae in rainwater wells in residential areas
    REN Zhi-hua, LIU Tian, CHEN Jia-xin, WANG Yu-feng, CHEN Zi-yi, ZHOU Yi-bin
    Chines Journal of Vector Biology and Control. 2021, 32(3): 374-377. https://doi.org/10.11853/j.issn.1003.8280.2021.03.023
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    Objective To investigate water accumulation and mosquito larvae breeding in rainwater wells in residential areas at mosquito density peaks as well as the effectiveness of 5% pyriproxyfen and fenthion granules in controlling the mosquitoes, and to provide a basis for the control of mosquito larvae in rainwater wells in the residential areas. Methods From August to September, 2019, 64 rainwater wells in the south and 58 rainwater wells in the north of a residential area in Qingpu, Shanghai, China were selected as experimental group and control group, respectively. The experimental group was given 5% pyriproxyfen and fenthion granules; water accumulation and mosquito larvae breeding in the rainwater wells were investigated before insecticide application and 1, 3, 7, 14, 21, and 28 days after insecticide application (7 investigations in total). Results Thirty-five (28.69%) rainwater wells had water accumulation during all the 7 consecutive investigations of 122 rainwater wells in the residential area, 12 (9.83%) rainwater wells had water accumulation during 1-6 of the 7 investigations, and 75 (61.48%) rainwater wells had no water accumulation during all the 7 investigations; the water accumulation rate of the rainwater wells were 30.33%-36.89% (χ2=1.176, P=0.278), and there was no significant correlation between water accumulation rate and precipitation 3 days before investigation (r=0.558, P=0.193). The positive rate of mosquito larvae breeding in the rainwater wells in the experimental group decreased to 16.67% 1 day after insecticide application, showing a significant difference compared to the positive rate (62.50%) before insecticide application (χ2=4.689, P=0.027); the concurrent positive rate of mosquito larvae breeding in the control group was 41.18%-55.56%, showing no significant difference (χ2=0.252, P=0.769); the positive rate of mosquito larvae breeding in the rainwater wells in the experimental group was 0 14 days after insecticide application; 23.81% 21 days and 38.46% 28 days after insecticide application, there were no significant difference compared to the control groups (all P>0.05). Conclusion From August to September, the water accumulation in the rainwater wells in the residential area in Qingpu is stable; 5% pyriproxyfen and fenthion granules can control the mosquitoes in the rainwater wells for about 2 weeks; therefore, it is recommended to regularly apply insecticides in long-term water accumulation to scientifically control mosquito larvae breeding in the rainwater wells.
    • Review
  • Research and application progress in biological control technology for hygiene pest control
    ZHANG Xiao, WANG Dong, XIN Zheng
    Chines Journal of Vector Biology and Control. 2021, 32(3): 378-384. https://doi.org/10.11853/j.issn.1003.8280.2021.03.024
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    Hygiene pests affect and threaten human health and life by means of harassing, biting, and spreading diseases. Chemical control is the main measure of hygiene pest control currently. However, with the growing problems of pesticide residue, pesticide resistance, and environmental pollution, and with the increasing awareness of environmental protection among people and the emergence of new and recurrent vector-borne diseases, the research and application of biological control have received much more attention. In recent years, some achievements have been made in the research and application of pathogenic microorganisms, plants, natural enemies, insect growth regulators, biotoxins, genetic engineering technology, and other aspects of hygiene pest control, and some safe, environmental-friendly, efficient, and economical biological products have been developed and produced. This article summarizes the previous research and application, which may provide a scientific basis and help for the further research and application of biological control technology in reducing the hygiene pest density and prevention and control of vector-borne diseases.
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