20 December 2024, Volume 35 Issue 6
    

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    Expert Forum
  • The current status and prospects of sustainable dengue vector Aedes management
    LIU Xiao-bo, REN Dong-sheng, LIANG Ying, YUE Yu-juan, LU Liang, LIU Qi-yong
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 633-638. https://doi.org/10.11853/j.issn.1003.8280.2024.06.001
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    Dengue fever, a vector-borne infectious disease caused by Dengue virus and transmitted by the bite of Aedes mosquitoes, has imposed a significant disease, economic, and social burden on both the global and China. Influenced by multi-dimensional driving factors including climate change, globalization, urbanization, and public health insecticide resistance, the risk of dengue transmission and outbreaks are escalating worldwide and in China. Currently, traditional surveillance and control technologies for Aedes vectors have already revealed certain limitations in preventing and controlling dengue. The research and development of innovative surveillance and control tools and products, as well as application technologies for Aedes vectors, are relatively insufficient, making it challenging to meet the demands of dengue prevention and control in the new era. In future, it is imperative to actively implement sustainable Aedes management, control Aedes vectors based on a graded response approach for dengue prevention, and comprehensively utilize various appropriate techniques. This will provide a solid foundation for the risk assessment, early warning, and scientific and precise prevention and control of dengue in China.
    • Experimental Study
  • Analysis of genomic single nucleotide polymorphisms of Yersinia pestis in the Sanjiangyuan region of Qinghai Province, China
    BAI Ji-xiang, JIN Juan, LI Sheng, XIN You-quan, YANG Xiao-yan, ZHANG Li, JIN Yong, LI Xiang, YING Kai-ye, HE Jian
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 639-643. https://doi.org/10.11853/j.issn.1003.8280.2024.06.002
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    Objective To investigate the characteristics of Yersinia pestis population structure in natural plague foci in the Sanjiangyuan region of Qinghai Province using genomic single nucleotide polymorphisms (SNPs) analysis, so as to provide a theoretical basis for plague prevention and control in this region. Methods A total of 81 representative strains of Y. pestis collected in the Sanjiangyuan region were selected for analysis of variations across 2 298 SNP sites based on whole genome sequencing data. MEGA 6.0 software was used to construct a phylogenetic tree. The structure and distribution characteristics of Y. pestis population in this region were analyzed. Results The 81 strains of were classified into three SNP genotypes, designated as 1.IN, 2.ANT, and 0.PE. The strains in the 1.IN subpopulation were dominant in the natural plague foci of the Sanjiangyuan region, and all of them were isolated from the natural plague focus of Marmotahimalayana. The strains in the 2.ANT and 0.PE subpopulations were distributed across Chengduo County, Nangqian County, and Qumalai County in Yushu Tibetan Autonomous Prefecture. The strains of Y. pestis isolated from the natural plague focus of Neodon fuscus in Qinghai belonged exclusively to the 0.PE4C subpopulation. Conclusion Genomic SNP analysis of Y. pestis subpopulations showed obvious regional distribution characteristics in the Sanjiangyuan region, which provides scientific tips for the epidemiological investigation of plague epidemic in this region.
  • The phenotypic characteristics of a Microtus strain of Yersinia pestis from Lasiopodomys brandtii with partial resistance to plague diagnostic phage
    LI Cun-xiang, QI Zhi-zhen, YANG Xiao-yan, LI Xiang, WU Hai-sheng, ZHANG Li, ZHANG Xiao-lu, ZHAO Hai-hong, JIN Juan, XIN You-quan
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 644-647. https://doi.org/10.11853/j.issn.1003.8280.2024.06.003
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    Objective To analyze the phenotype characteristics of Yersinia pestisMicrotus strain 90017 from Lasiopodomys brandtii, so as to provide a theoretical basis for investigating mechanisms of bacterial resistance to phages, the long-term preservation mechanisms of Y. pestis in plague foci, and evolutionary epidemiology of infectious diseases. Methods BALB/c mice were infected subcutaneously with 3 concentrations of Microtus strain of Y. pestis respectively including 2×109,1×106 and 1×105 pieces /ml. Animals are dissected after death to isolated Y. pestis. It were observed on cultural characteristics and plague phage lytic test of Y. pestisMicrotus strain 90017. Result Y. pestis 90017 was cultured in a solid medium at 28°C for 24 hours before and after animal experiment, and it was found that the bacterial growth was slow. The bacterial colony showed typical morphology of Y. pestis after 48-100 hours of incubation. After a 24-hour bacteria lysed at 28°C in plague phage lysis test, the center of phage lysis zone demonstrated the appearance of broken glass and untypical debris of colonies. After 48-100 hours of incubation, in addition to the eroded residual colonies, some relatively complete colonies remained in the test zone where plague phage dripped and flowed through. The areas marked with the control Y. pestis strain 141 showed obvious bacterial lawn, and there was no bacterial growth in the areas where plague phage dripped and flowed through. The resulting phage lysis zone was wider than the trace left by the phage flow. The bacterium 90017 did not recover to its typical state after animal experiment, which was similar to its growth state and the result of plague phage lysis test for plague before animal experiment. Conclusion The coexistence of plague diagnostic bacteriophage-sensitive and -resistant strains in Microtus strain of Y. pestis 90017 from L. brandtii reflects biological complexity of microbial community in natural environment, which may play an important role in maintaining the epidemic and infection process of pestis.
  • Metabolism of two insecticide effective ingredients in Blattella germanica and Periplaneta americana
    TANG Li-ping, LAI Yun-yan, LIANG Ze-quan, ZHU Jian
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 648-651. https://doi.org/10.11853/j.issn.1003.8280.2024.06.004
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    Objective To investigate the differences in feeding amount and intestinal metabolism of Blattella germanica and Periplaneta americana on 2.5% imidacloprid and 0.5% dinotefuran cockroach baits, so as to provide a theoretical basis for the difference research on lethal speed of these two effective ingredients in B. germanica and P. americana. Methods The feeding amounts of B. germanica and P. americana on baits was measured, and intestinal dissection and fecal collection were conducted. Liquid chromatography was used to analyze the content of two effective constituents in the intestinal tract and feces, and the midgut metabolic rate and digestive tract metabolic rate were calculated. The differences in the data were compared by the independent samples t test. Results The feeding amounts of B. germanica and P. americana on the two baits was significantly lower than that on the normal baits [ In B. germanica, dinotefuran: (7.56±0.79) mg/cockroach, t=-62.310, P<0.001; imidacloprid: (0.66±0.29) mg/cockroach, t=-25.873, P<0.001. In P. americana, dinotefuran: (9.53±0.58) mg/cockroach, t=-34.067, P<0.001; imidacloprid: (2.72±0.28) mg/cockroach, t=-27.191, P<0.001]. The digestive tract metabolic rate and midgut metabolic rate of 2.5% imidacloprid bait were 96.17% and 81.04% in B. germanica, and 92.71% and 97.01% in P. americana, respectively, with no significant difference between the two species (F=7.290, P=0.054; F=5.436, P=0.080). The digestive tract and midgut metabolic rates of 0.5% dinotefuran bait were 54.69% and 78.82% in B. germanica, while dinotefuran was not detected in the anterior, middle, and posterior intestines and feces of P. americana. Conclusions Both B. germanica and P. americana exhibit significant resistance to imidacloprid and dinotefuran baits, which may be one of the reasons for the difference in lethal speed of the two baits and the main reason for the poor lethal effect of dinotefuran on P. americana. Digestive tract metabolism is not the reason for the difference in lethal speed of the two baits.
  • Killing effect of unmanned aerial vehicle spraying at different locations against Aedes albopictus： A study based on the hanging cage method
    GUO Yu-hong, LIN Jun-fen, HUANG Wen-zhong, GUO Song, MENG Feng-xia, WU Hong-zhao, LIU Xiao-bo, WU Yu-yan, LU liang, YAN Dong-ming, HOU Juan, GONG Zhen-yu, ZHANG Rong, CHEN En-fu, LIU Qi-yong
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 652-656. https://doi.org/10.11853/j.issn.1003.8280.2024.06.005
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    Objective To evaluate the killing effect of unmanned aerial vehicle (UAV) spraying at different locations in residential areas against mosquitoes by the hanging cage method, so as to provide a reference method for the evaluation of mosquito control effect by spraying on site, and to provide a basis for the prevention and control of mosquitoes and mosquito-borne diseases. Methods Two residential areas (villages) were selected in Pujiang County, Zhejiang Province, China. The mosquito cages for feeding containing Aedes albopictus were hanging in various scenes such as the open environment on the ground, sparse branches, and under dense trees, and all the locations were under the UAV spraying. The mortality rate of Ae. albopictus in mosquito cages at different locations at different time points was calculated and compared with that in the control cages by the Chi-square test and Fisher's exact test. Results After the UAV spraying, for the sensitive strains of Ae. albopictus, all were killed within 2.5 h in the open environment; on sparse branches, the mortality rate reached 90.21% at 2.2-2.5 h, 94.89% at 4.5-5.0 h, and the highest (99.15%) at 10.0 h; under dense trees, the mortality rate reached 82.74% at 2.2-2.5 h, 91.15% at 4.5-5.0 h, and the highest (96.02%) at 10.0 h; the highest mortality rates of mosquitoes in the three environments were in descending order, without significant differences (P=0.190). For the local populations of Ae. albopictus, the mortality rate reached 77.63% within 2.2-2.5 h and 94.74% at 4.5-5.0 h in the open environment. Conclusions The hanging cage method is an effective method to evaluate the killing effect of UAV spraying against mosquitoes. The UAV spraying shows a good killing effect on Ae. albopictus in cages in the open environment, on sparse branches, and under dense trees. The UAV spraying is an effective adult mosquito killing method in the urban residential environment.
    • Vector Surveillance
  • An analysis of fly ecological surveillance results in Hebei Province, China, 2011-2023
    MA Li-hua, GAO Wen, WANG Xi-ming, ZHANG Xiao-jie, LI Bing, ZHAO Li-ping, HAN Xiao-li, SONG Ji-wen, ZHAO Yong
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 657-663. https://doi.org/10.11853/j.issn.1003.8280.2024.06.006
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    Objective To investigate the species composition, density, habitat distribution, and seasonal fluctuations of fly in Hebei Province, China, so as to provide a scientific basis for fly control in Hebei Province. Methods From April to November in 2011 to 2023, fly density was monitored using cage traps with sugar-vinegar baits at four types of habitats (farmers' markets, catering surroundings, green belts, and residential areas) in the fly surveillance areas of 17 cities and counties. WPS Excel 11.1.0.11045 and R 4.2.2 softwares were used to process the data. The species composition of fly was analyzed and fly density and fluctuations between different species were compared in different years, months, habitats and regions by using the Chi-square test, t-test, analysis of variance, Kruskal-Wallis H test, and Friedman test. Results From 2011 to 2023, a total of 9 349 cages were placed in Hebei Province, trapping a total of 42 647 flies, with an average density of 4.56 flies/cage. The dominant populations were Musca domestica, Muscina stabulans, Sarcophagidae flies, and Lucilia sericata, accounting for 52.91%, 13.46%, 9.26%, and 5.54% of the total catches, respectively. In 2019-2023, the total density of flies in Hebei Province showed a downward trend. Fly total density showed a single peak in August at a density of 7.25 flies/cage, and the unimodal pattern occurred in all habitats, with peaks in July to August. Among the four types of habitats, the density of flies in farmers' markets was highest, reaching 6.13 flies/cage, followed by residential areas, green belts, and catering surroundings, showing a significant difference in fly density between different habitats (Q=26.012, P<0.001). Fly density was highest in farmers' markets from 2011 to 2020 and highest in green belts from 2021 to 2023, with a significant difference in annual density fluctuation between different habitats (F=15.541, P<0.001). The average fly density in southern Hebei was 5.88 flies/cage, while that in the northern region was 3.98 flies/cage, which were significantly different (t=-3.055, P=0.009). Conclusions The focus of fly control in Hebei Province should be on Musca domestica, Muscina stabulans, Sarcophagidae flies, and L. sericata and in farmers' markets. In recent years, the density of flies in green belts has increased. The peak period of fly activity is from July to August. The control measures should be taken before the peak period according to the law of fly activity in different regions of Hebei Province.
  • Surveillance analysis of host animals of hemorrhagic fever with renal syndrome in Yuanzhou District, Guyuan, Ningxia Hui Autonomous Region, China, 2020-2023
    LI Tao, HOU Hai-long, LI Ming-zhu, ZHAN Jun, GONG Rui, YANG Dong-zhi
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 664-670. https://doi.org/10.11853/j.issn.1003.8280.2024.06.007
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    Objective To analyze the surveillance data on host animals of hemorrhagic fever with renal syndrome (HFRS) in Yuanzhou District, Guyuan, Ningxia Hui Autonomous Region, China, to determine the distribution and infection status of host animals of HFRS, so as to provide a basis for the prevention, control, early warning, and prediction of HFRS in the area. Methods From 2020 to 2023, small mammals were captured by the night-snap trapping method in both the wild area and residential area in Yuanzhou District, Guyuan in the spring and autumn in accordance with the National Surveillance Program for Hemorrhagic Fever with Renal Syndrome. Taxonomic identification was conducted, and the density and distribution characteristics of small mammals were analyzed. Lung and blood samples were collected from the trapped small mammals for detection of Hantavirus antigens using direct immunofluorescence method and antibodies with enzyme-linked immunosorbent assay (ELISA). SPSS 26.0 software was used for statistical analysis. The rates were compared using the Chi-square test. Results A total of 795 small mammals were captured from 2020 to 2023. The annual density of small mammals was less than 2.00% capture rate. The small mammal density was higher in autumn than in spring (χ2=22.326, P<0.001), and higher in the residential area than in the wild area (χ2=278.319, P<0.001). The density of small mammals in the wild area of each surveillance town was less than 1.00%, where the small mammals captured were mainly Apodemus agrarius (38.14%), Cricetulus longicaudatus (29.38%), and A. peninsulae (18.56%). The density of small mammals in the residential area was greater than 1.00%, where the small mammals captured were Rattus norvegicus (62.06%) and Mus musculus (37.94%). The proportion of A. agrarius in the wild area and R. norvegicus in the residential area in autumn was higher than that in spring (χ2=6.269, P=0.012; χ2=52.511, P<0.001). The antibody positive rate in blood samples of the captured small mammals was higher than the antigen positive rate in lung samples (χ2=187.756, P<0.001). Hantavirus was only detected in A. agrarius and A. peninsulae in the wild area. The infection rate of M. musculus in the residential area was higher than that of R. norvegicus (χ2=22.340, P<0.001). Conclusions The current overall density of small mammals in Yuanzhou District, Guyuan is relatively low, with residential areas having higher densities than wild areas and autumn being higher than spring. It is recommended to strengthen surveillance, deratization, vaccination work, while improving the early identification, diagnosis and treatment capacity of medical personnel for HFRS.
    • Vector-borne Disease
  • Epidemic characteristics and infection sources of severe fever with thrombocytopenia syndrome in Hangzhou, China from 2014 to 2023
    ZHU Lei, TAO Ming-yong, WANG Zhe, HUANG Ren-jie, SONG Kai, REN Xiao-bin, SUN Zhou
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 671-675. https://doi.org/10.11853/j.issn.1003.8280.2024.06.008
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    Objective To analyze the population, regional, and time distribution characteristics and infection sources of severe fever with thrombocytopenia syndrome (SFTS) in Hangzhou, China from 2014 to 2023, so as to provide evidence for the prevention and control of SFTS. Methods The cases data of SFTS in Hangzhou from 2014 to 2023 were collected from the China Information System for Disease Control and Prevention. Descriptive epidemiological methods were used to analyze the distribution characteristics and infection sources of SFTS cases. The spatial map was plotted with ArcGlS 10.2 software, and the Mann-Kendall Z trend test was carried out with R 4.3.0. Results A total of 90 SFTS cases were reported in Hangzhou from 2014 to 2023, with an average annual reported incidence of 0.08/100 000 and an average fatality rate of 15.56% (14/90). The overall incidence rate of SFTS in Hangzhou City has shown an overall upward trend (Z=1.789, P=0.037), and the incidence rate of SFTS rose rapidly in 2023. There were 46 males and 44 females with a sex ratio of 1: 0.96. The high incidence was observed in the middle-aged and elderly population (≥45 years old), accounting for 92.45% (86/90). Farmers were the main occupation, accounting for 81.11% (73/90). The onset was mainly in summer in the early stage and increased to the whole year over years, with the majority in spring, summer, and autumn. From 2014 to 2023, the number of SFTS cases reported in Hangzhou increased from 1 (Chun'an County) to 8 counties (cities or districts) year by year. with the largest number of cases in Chun'an County (50 cases), followed by Lin'an District (26 cases) and other counties (cities or districts,<5 cases). The analysis of sources of infection showed that 5 cases were infected from contact with SFTS deaths. Among the other infected cases (n=85), 18 (21.18%) had a definite history of tick bites 2 weeks before the onset, 37 (43.53%) denied the history of tick bites, and 30 (35.29%) had unknown sources of infection. Conclusions The incidence of SFTS in Hangzhou gradually expanded, and the incidence trend of reported cases also increased significantly. The sources of infection include tick bites and contact infection. The prevention and control of SFTS should be strengthened on case surveillance, epidemic response, and integrated control of ticks.
  • Epidemiological characteristics of scrub typhus in Qingdao, Shandong Province, China, 2006-2022
    PAN Bei, DONG Li-yan, HAN Ya-lin, HU Xiao-wen, JIA Jing, LYU Kun-zheng
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 676-680. https://doi.org/10.11853/j.issn.1003.8280.2024.06.009
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    Objective To analyze the time, regional, and population distribution of scrub typhus cases reported in Qingdao, Shandong Province, China, so as to provide a scientific basis for the prevention and control of scrub typhus in the future. Methods The information on scrub typhus cases in Qingdao from 2006 to 2022 was collected and statistically analyzed by Excel 2010 and SPSS 22.0 softwares. The incidence rate as well as characteristics and variation trends of time, regional, and population distribution of scrub typhus were analyzed by the joinpoint regression and Chi-square test. Results From 2006 to 2022, 1 112 cases of scrub typhus were reported in Qingdao, with an average annual incidence of 0.74/100 000, and no death cases were reported. Scrub typhus cases were reported from March to December, of which October and November were the peak months of reported incidence, with cases accounting for 96.13% of the total cases. Scrub typhus cases were reported in all age groups, with a significant difference in the incidence rate (χ2=1 266.119, P<0.001). Males in the 60-<65 years old group (93 cases) and females in the 55-<60 years old group (106 cases) had the highest cases reported. The top five cities (districts) in average annual incidence were Laixi City (2.42/100 000), Jimo District (1.49/100 000), Huangdao District (1.11/100 000), Jiaozhou City (0.58/100 000), and Pingdu City (0.40/100 000), with a significant difference in the reported incidence (χ2=1 050.577, P<0.001). Farmer (85.16%) was ranked the first in occupation for scrub typhus infection. Conclusions The incidence of scrub typhus in Qingdao from 2006 to 2022 presents significant regional and seasonal variations. Farmers are at high risk of scrub typhus. It is suggested that extensive health education about scrub typhus prevention and control should be carried out for key populations in key areas, and multiple effective measures should be taken to strengthen the surveillance of vectors and host animals and control the infection level of scrub typhus.
  • Epidemic characteristics of plague in the plague foci of Spermophilus dauricus in Inner Mongolia Autonomous Region, China, 2013-2022
    FENG Yi-lan, YU Xin-xin, FAN Meng-guang, LI Jian-yun, ZHANG Da-yu, ZHANG Zhong-bing
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 681-686. https://doi.org/10.11853/j.issn.1003.8280.2024.06.010
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    Objective To analyze the species composition and dencity of host animals and vector fleas and the epidemiological characteristics of animal plague in the plague foci of Spermophilus dauricus in Inner Mongolia Autonomous Region (Inner Mongolia), China, so as to provide scientific evidence for plague prevention and control. Methods Descriptive epidemiology methods were used to analyze the surveillance and epidemic data in the plague foci of S. dauricus in Inner Mongolia from 2013 to 2022. Excel 2019 software was used for data collation and calculation, and SPSS 19.0 software for statistical analysis. The flea infestation rates were compared by the Chi-square test; the rodent density and the index of rodent body fleas were compared by the t test; the index of burrow fleas and nest fleas were compared by the Wilcoxon rank sum test. Results In Songliao Plain, a total of 61 756 individuals from 20 species of host animals were captured, with 44 299 individuals from 12 species of fleas obtained; the mean density of S. dauricus was 0.45 inds/hm2. In Qahar Hills, 14 096 individuals from 19 species of host animals were captured, with 42 713 individuals from 15 species of fleas obtained; the mean density of S. dauricus was 2.26 inds/hm2. No outbreaks occurred in Songliao Plain. Animal plague outbreaks occurred in two banners (districts) in Qahar Hills over the four years, with four strains of Yersinia pestis from Meriones unguiculatus isolated and two positive serum samples of S. dauricus detected. Conclusions The epizootic plague in Songliao Plain remains in a resting state at present, while that in Qahar Hills is active. M. unguiculatus plague and S. dauricus plague are prevalent simultaneously. The epidemic situation is complex.
  • Investigation and epidemic risk analysis of new plague foci and vicinal regions in Jinghong, Yunnan Province, China
    PU En-nian, XU Ding-cong, SU Chao, SU Li-qiong, DUAN Biao, YA Hong-xiang, REN Jian-nan, ZOU Jian-hong, TAN Li-tao, GAO Zi-hou
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 687-691. https://doi.org/10.11853/j.issn.1003.8280.2024.06.011
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    Objective To investigate host animals in new plague foci with a new outbreak in 2016 and vicinal regions in the plague foci of Rattus tanezumi in Jinghong, Yunnan Province, China, and to determine the epidemic situation and risk of plague among animals, so as to provide a basis for plague monitoring, prevention, and control in this area. Methods An investigation was carried out on host animals and vectors in the plague foci in Puwen Town and Dadugang Township, Jinghong City in September 2022. Bacteriological, serological, and molecular biological laboratory tests were conducted on the visceral organs, serums, and parasitic fleas of small mammals captured and collected. Results A total of 61 small mammals were obtained, which belonged to 7 species from 4 genera, 3 families, and 2 orders. R. tanezumi accounted for 79.66% and was the dominant species. A total of 35 parasitic fleas were collected on the body surface of small mammals, all of which were Xenopsylla cheopis. The flea index ranged from 1.00 to 2.00 in the residential area and from 0.00 to 0.38 in the wild area. Of 119 samples (induding 2 samples for reverse indirect hemagglutination assay) for testing serologically, 61 small mammal samples and 35 flea samples for testing bacteriologically, and 4 DNA samples from small mammals detected by quantitative real-time polymerase chain reaction, two F1 antibody-positive serum samples of R. tanezumi were detected. No Yersinia pestis was isolated and no specific gene fragment of Y. pestis was detected. Conclusions Main host animals and vector fleas of plague are widely distributed in Puwen Town and vicinal regions in Jinghong, and the capture rate of host animals and their flea index are relatively high in some areas, indicating an epidemic risk of plague. It is suggested that preventive rodent and flea control should be carried out in time in areas with high capture rate of host animals and flea index, and continuous plague monitoring should be strengthened to prevent the occurrence of human plague.
  • Epidemic characteristics of severe fever with thrombocytopenia syndrome and surveillance of infection in ticks and animals in Shengzhou, Zhejiang Province, China, 2016-2023
    QIAN Jia-wen, SHEN Yu-gang, WANG Hong-wei, OU Xiao-yang, ZHANG Ling, LI Yan, REN Li-bo, ZHU Lu-bin, XIAO Zhao-ying
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 692-698. https://doi.org/10.11853/j.issn.1003.8280.2024.06.012
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    Objective To analyze the epidemic characteristics of severe fever with thrombocytopenia syndrome (SFTS) and monitor the infection of host animal, vectors, and human populations in Shengzhou, Zhejiang Province, China, 2016-2023, so as to provide a scientific basis for the development of prevention and control strategies. Methods The population, temporal, and spatial distributions, epidemiological history, clinical characteristics, and hospital visit of SFTS cases were analyzed using the descriptive epidemiological method. Chi-square test and Mann-Whitney U test were used to analyze differences between groups. SFTS cases from 2016 to 2023 were obtained from the China Disease Prevention and Control Information System and epidemiological investigations of the cases. Serum samples of healthy people and host animals were collected for detection of Dabie bandavirus antibody. On-host and free-living ticks were monitored using animal body surface examination and the drag/flag sampling method. Dabie bandavirus in host animals and ticks was detected by real-time fluorescence quantitative PCR. Results From 2016 to 2023, 27 cases of SFTS were reported, of which 17 cases in 2023, including 10 (37.04%) males and 17 (62.96%) females, with an average annual incidence of 0.56/100 000 and a fatality rate of 22.22%. Moreover, 23 (85.19%) cases were local farmers engaged in tea picking and agriculture. The age of onset ranged from 51 to 94 years, with a median of 68 years. The incidence showed significant seasonality, mainly from April to August. Circular distribution analysis showed that the peak of the disease occurred between May 11 and August 29. Locally transmitted cases were reported in 9 out of 15 townships (streets). All cases had a history of field activities 2 weeks before onset. The main clinical manifestations were fever (96.30%), fatigue (81.48%), loss of appetite (59.26%), leukopenia (96.30%), and thrombocytopenia (88.89%). In 2023, the median time from onset of symptoms to hospital visit was 3.0 days, and the median time from visit to diagnosis was 2.0 days. One case was diagnosed after 4 visits, and 10 (58.82%) cases were diagnosed after 1 visit. The positive rate of Dabie bandavirus antibody in the serum of healthy population was 2.50%. A total of 35 free-living ticks were captured in Shengzhou from 2016 to 2023, with a mean density of 0.23 ticks/(flag·100 m). Additionally, 417 parasitic ticks were captured, with a mean on-host tick index of 4.53. Of host animals, sheep, cattle, and dogs were positive for Dabie bandavirus antibody in serum, and the positive rates were 27.69%, 11.11%, and 6.67%, respectively. Ticks and host animals were negative for Dabie bandavirus nucleic acids. Conclusions The incidence of SFTS in Shengzhou increased rapidly in 2023. There may be a natural epidemic focus of SFTS in Shengzhou. The epidemic showed significant seasonality, and elderly farmers were at high risk. It is necessary to strengthen the publicity and education regarding SFTS, implement environmental remediation and vectors control, and improve the diagnosis and treatment levels of primary medical institutions.
  • Epidemiological analysis of animal plague in the plague foci of Lasiopodomys brandtii in Inner Mongolia Autonomous Region, China, 2013-2022
    HAN Bing, LI Jian-yun, ZHANG Da-yu, LIU Hui-jie, GUO Wen-xiu, ZHANG Zhong-bing
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 699-703. https://doi.org/10.11853/j.issn.1003.8280.2024.06.013
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    Objective To analyze the epidemiological characteristics of animal plague in the plague foci of Lasiopodomys brandtii in Inner Mongolia Autonomous Region (Inner Mongolia), China, so as to provide a scientific basis for the formulation of plague prevention and control strategies. Methods The surveillance data in the plague foci of L. brandtii in Inner Mongolia during 2013-2022 were collected. The density of L. brandtii, capture rate of nocturnal rodents, flea infestation rate of vectors, etiological and serological positive rates, and annual percentage change (APC) were calculated. The joinpoint regression analysis of Joinpoint regression program 3.4.3 software was used for trend analysis of density, capture rate, and flea infestation rate. Results During 2013-2022, the mean density of L. brandtii in the plague foci of L. brandtii in Inner Mongolia was 2.36 inds/hm2, and the density showed a decreasing trend and an APC of -21.69%, with a significant difference in annual densities as shown by the trend analysis (Z=-3.133, P=0.014). The mean capture rate of nocturnal rodents was 1.27%, and the capture rate showed a decreasing trend and an APC of -4.75%, with no significant annual difference (Z=-1.136, P=0.289). The mean flea infestation rate of L. brandtii was 33.96%, with a flea index of 0.86, and the flea infestation rate showed a decreasing trend and an APC of -5.48%, with no significant annual difference (Z=-1.292, P=0.233). A total of 19 593 host animals were examined etiologically, and 6 animals tested positive for Yersiniapestis, all of whom were Meriones unguiculatus, showing a positive rate of 0.03%. Conclusions The number and distribution of L. brandtii showed a decreasing trend in the plague foci of L. brandtii, and the plague epidemic of M. unguiculatus was in an active stage. Routine surveillance should be strengthened to detect and control the animal epidemic in time and effectively reduce the epidemic strength of animal plague and the risk of human plague infection.
  • Species composition and spatial distribution of parasitic fleas of small mammals in Sino-Russian border port areas in Heilongjiang Province, China
    WANG Dong-wei, CHEN Qi, LIANG Hong, WANG Si-zhe, CHEN Lin-lin, NIU Lei, YU Shi-wei, LIANG Hui-jie
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 704-708. https://doi.org/10.11853/j.issn.1003.8280.2024.06.014
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    Objective To investigate the species composition and distribution of parasitic fleas of small mammals in Sino-Russian border port areas in Heilongjiang Province, China. Methods The surveillance data and relevant references on parasitic fleas of small mammals in 11 Sino-Russian border port areas in Heilongjiang Province from 2007 to 2023 were collected to descriptively analyze flea species composition and distribution. Results A total of 44 species (subspecies) of 24 genera of 5 families were identified for the parasitic fleas of small mammals in Sino-Russian border port areas in Heilongjiang Province. The fleas in the Suifenhe port areas possess the most diversity,reaching 30 species and subspecies. Conclusion The species and distribution of fleas in the important frontier ports in Heilongjiang were studied,which provided the basic data for risk analysis and prevention and control of flea borne diseases at frontier ports in Heilongjiang.
  • Seasonal variation of ticks in Yantai, Shandong Province, China： A study based on the circular distribution method
    LI Chun-hui, YANG Yi-min, MIAO Xiu-jing, SUN Jing, ZHANG Yong, LIU Cheng-juan, WANG Ting, DENG Wen-hai
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 709-713. https://doi.org/10.11853/j.issn.1003.8280.2024.06.015
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    Objective To investigate the seasonal variation of on-host and questing ticks in Yantai, Shandong Province, China, so as to provide a scientific basis for the control planning development and the control and prevention of ticks and tick-borne diseases. Methods From March to October in 2021-2023, questing ticks were collected in the wild by the tick drag-flag method in nine districts (cities) of Yantai, and on-host ticks on the body surface of domesticated animals (cattle, sheep, and dog) were collected by tick detection method. The monthly distribution data of ticks in 2021-2023 were obtained and analyzed with the circular distribution method for the peak days and peak periods of questing ticks in different habitats and on-host ticks in different host animals. Results The γ values of questing ticks in various habitats and on-host ticks in various hosts in Yantai ranged from 0.594 to 0.908 (P<0.05), showing obvious seasonality. The peak period of seasonal variation in questing ticks appeared from May 18 to September 13, with the peak day on July 16, and that in on-host ticks appeared from May 14 to August 28, with the peak day on July 6. The peak periods of seasonal variation in questing ticks from rural external environment rural areas and scenic areas appeared from May 19 to September 15 and May 17 to July 21, with the peak days on July 17 and June 18, respectively, and those in on-host ticks on the body surface of cattle, sheep, dogs (rural areas), and dogs (urban areas) appeared from August 24 to October 14, May 13 to August 26, May 18 to September 8, and June 1 to July 31, with the peak days on September 19, July 5, July 14, and July 1, respectively. Conclusions Questing and on-host ticks in Yantai show a seasonal distribution. The seasonal characteristics of questing and on-host ticks should be fully considered in the control of ticks, with targeted control measures being taken. According to the changes in tick density, personal protection should be done to minimize exposure, and scientific tick extermination should be carried out to reduce the incidence of tick-borne diseases.
    • Investigation
  • Investigation of Rickettsia and Ehrlichia harbored by Haemaphysalis longicornis in Yingkou City, Liaoning Province, China
    LIU Zi-wei, LI Hua-feng
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 714-718. https://doi.org/10.11853/j.issn.1003.8280.2024.06.016
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    Objective To investigate the prevalence of Rickettsia and Ehrlichia harbored by Haemaphysalis longicornis in Yingkou City, Liaoning Province, China. Methods A total of 138 free-living ticks were collected using the drag-flag method in Gaizhou county-level City of Yingkou, Liaoning Province. All the ticks were identified as H. longicornis. The samples were pooled for DNA extraction and screened for genera Rickettsia and Ehrlichia using primers targeting their 16S rDNA genes by nested PCR. Subsequently, the gltA, groEL, and 16S rDNA gene sequences were amplified. All the obtained sequences were subjected to genetic and phylogenetic analyses using BLASTN and PhyML 3.0 softwares, respectively. Results Three pooled samples tested positive for Rickettsia, and the species in all samples were identified as Candidatus Rickettsia jingxinensis by sequencing analysis. The 16S rDNA, gltA, and groEL genes showed 100%, 100%, and 99.04% identities to previously reported strains. Moreover, four pooled samples tested positive for Ehrlichia sp., and 16S rDNA gene sequencing showed 100% identity to Candidatus E. shimanensis, Ehrlichia sp. Yonaguni 206, and Candidatus E. pampeana. Moreover, the groEL gene showed 100% identity to Ehrlichia sp. Yonaguni 138, and the gltA gene showed 99.62% identity (56% coverage) to uncultured Ehrlichia sp. clone SY130 and 82.85% identity to E. ewingii. Conclusion The prevalence of Rickettsia and Ehrlichia in ticks from Yingkou of Liaoning Province suggests the potential risk of human infections.
  • Investigation of rash outbreak caused by larvae of Euproctis bipunctapex in a residence community in Pudong New Area, Shanghai, China, 2023
    LIU Jing-yi, GU Ying-pei, YUAN Yong-ting, YU Si-yu, LIU Jun, GE Ge, LI Hui-hui, LIU Han-zhao
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 719-722. https://doi.org/10.11853/j.issn.1003.8280.2024.06.017
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    Objective To explore the cause of and risk factors for an clusters of unexplained rashes of residents occurred in a residence community in Pudong New Area, Shanghai, China in 2023. Methods Case studies were conducted on symptomatic residents in July 2023. Environmental surveys were carried out on the community. Epidemiological characteristics of cases were described. Meanwhile, case-control studies were conducted, and pest species were identified. SPSS 26.0 software and Chi-square test were used to statistically analyze the data of different groups. Univariate logistic regression analysis was used for risk factor analysis. Results A large number of Lepidoptera larvae were found on the Chinese tallow trees and street lamps in front of the building where the cases gathered, and they were identified as Euproctis bipunctapex. The body part with the highest incidence rate of rashes was the upper limbs (84.34%), and that with the lowest incidence rate of rashes was the head and face (7.23%). The attack rates of rashes among residents living less than 50 meters, between 50 meters and 100 meters, and greater than 100 meters away from allergens were 81.32%, 75.00%, and 25.00%, respectively, with significant differences (χ2=26.407, P<0.001). The highest attack rate was observed in the age group of >60 years, followed by the age groups of >50-60 years and >20-30 years. Staying within 50 meters away from allergens [odds ratio (OR)=14.79, 95% confidence interval (CI): 5.73-38.17, P=0.001] and drying quilts and clothes in the open space of the community in the last month (OR=2.37, 95% CI: 1.05-5.36, P=0.038) were risk factors for rashes. Conclusions This clusters of unexplained rashes that occurred in residents in a residence community in Pudong New Area, Shanghai in 2023 is an outbreak of allergic rash caused by larvae of E. bipunctapex, whose poisonous hairs are dispersed by the wind and cause allergic rashes in contact with human skin. Drying quilts within the dispersing range of the poisonous hairs of larvae of E. bipunctapex also causes allergic rashes.
  • Species composition and spatial distribution of small mammals and their parasitic fleas in the Chongqing section of the Three Gorges Reservoir area
    XIAO Han-sen, HE Ya-ming, TU Tao-tian, WANG Zheng, ZHANG Ying, WEI Jing, JI Heng-qing
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 723-727. https://doi.org/10.11853/j.issn.1003.8280.2024.06.018
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    Objective To investigate the species composition and distribution of host animals and vector fleas of Yersinia pestis in Chongqing section of the Three Gorges Reservoir area, evaluate the presence of Y. pestis in these animals, and predict the potential risk of plague occurrence in the area. Methods From 2017 to 2022, an investigation was carried out in eight districts or counties along the Chongqing section of the Three Gorges Reservoir area, namely Fuling, Wanzhou, Kaizhou, Fengdu, Zhong County, Yunyang, Fengjie, and Wushan. Small mammals were captured by cage trapping method alongside the reservoir. The small animals and their parasitic fleas were identified and recorded. The data were used for descriptive analysis of their community structure characteristics. Chi-square test or Fisher's exact test was used to analyze differences between groups. Results A total of 403 small animals of 11 species were captured in 20 123 cage traps. The total density was 1.92%. Rattus tanezumi was the dominant species (62.28%), followed by Mus musculus (14.14%), R. norvegicus (8.68%), Crocidura attenuate (4.47%), Apodemus agrarius (3.47%), Anourosorex squamipes (3.23%), Niviventer confucianus (1.99%), R. nitidus (0.74%), R. losea (0.50%), N. fulvescens (0.25%), and Leopoldamys edwardsi (0.25%). The species composition of small mammals in 8 districts and counties in Chongqing section of the Three Gorges Reservoir area showed significant differences (P<0.001). The small mammal density was relatively high in Fengdu County (2.88%), Fuling District (2.71%), Fengjie County (2.53%), and Yunyang County (2.52%). The density was relatively low in Zhong County (1.83%), Wanzhou District (1.38%), and Kaizhou District (1.00%). The small mammal density was significantly different among 8 districts and counties (χ2=57.443, P<0.001). A total of 151 small mammals carried ectoparasitic fleas. A total of 1 034 parasitic fleas in 3 species were captured. The total flea infection rate was 37.47%, and the total flea infection index was 2.57. In addition, the flea infection rates were significantly different among districts and counties (χ2=54.534, P<0.001). Eight small animal species were infected with fleas, and their flea infection rates were significantly different (P=0.003). The vast majority of captured fleas were Leptopsylla segnis (1 031 individuals), 2 fleas were Monopsyllus anisus, and 1 flea was Ctenocephalides felis. Blood samples collected from all 403 live rodents tested negative for the serum antibody of Y. pestis F1. Conclusions The risk of plague epidemic among animals and humans is relatively low in the Chongqing section of the Three Gorges Reservoir area. However, continuous surveillance should be conducted to remain vigilant for the potential risk of plague and other rodent-borne diseases caused by the mixing of populations of domestic and wild small mammals and their ectoparasitic fleas, as well as the introduction of non-native species.
  • An investigation of rodent-borne pathogens in small mammals in the Chongqing section of the Three Gorges Reservoir area, China, 2022-2023
    WANG Ling, XIAO Han-sen, HE Ya-ming, ZHAO Ting, LI Zhi-feng, HUANG Wei
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 728-733. https://doi.org/10.11853/j.issn.1003.8280.2024.06.019
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    Objective To investigate the prevalence of five rodent-borne pathogens in small mammals in the Chongqing section of the Three Gorges Reservoir area, China, so as to provide scientific guidance for the prevention and control of rodent-borne diseases in the region. Methods From 2022 to 2023, small mammals were captured using the night snap (cage) trapping method in residential areas, cultivated lands, and key industries in the Chongqing section of the Three Gorges Reservoir area. Liver, spleen, and kidney tissues were collected to extract nucleic acids for the detection of Yersinia pestis, Bartonella, Borrelia burgdorferi, Leptospira, and Orientia tsutsugamushi using quantitative real-time PCR (qPCR). Blood samples from the heart were collected to detect Y.pestis F1 antibody, B. burgdorferi IgG antibody, and Leptospira serum antibody using serological methods. Excel 2016 and the SPSS 22.0 softwares were used for data processing and analysis. The pathogen infection rates of small mammals were compared using the Chi-square test or Fisher's exact test. Results A total of 361 small mammals belonging to 10 species were captured, with Rattus tanezumi and R. norvegicus being the dominant species, accounting for 53.46% and 12.47%, respectively. Detection of liver, spleen, and kidney tissues showed that 9 samples (2.50%) were positive for Leptospira and 17 samples (4.71%) were positive for Bartonella. No samples tested positive for Y. pestis, B. burgdorferi, or O. tsutsugamushi. The overall pathogen infection rates of small mammals were 6.65%. Co-infection of Leptospira and Bartonella was detected in R. tanezumi, and the co-infection rate was 0.55%. Animal serum antibody test results showed that 2 samples (0.80%) were positive for B. burgdorferi IgG antibody, 4 samples (1.59%) were positive for Leptospira antibody, and no samples were positive for Y. pestis F1 antibody. Conclusions Small mammals in the Chongqing section of the Three Gorges Reservoir area carry a variety of pathogens including Leptospira, Bartonella, and B. burgdorferi. Surveillance of rodent-borne pathogens carried by small mammals in this region should be enhanced and rodent prevention and control measures should be actively implemented to safeguard the public health of local residents.
  • Surveillance of main host animals of Leptospira and its antibodies in human population in Baiquan Town, Dinghai District, Zhoushan, Zhejiang Province, China
    ZHANG Sen, HU Ming-xing, TAN Qi-long, WANG Zhong-fa, WENG Yong-fu
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 734-739. https://doi.org/10.11853/j.issn.1003.8280.2024.06.020
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    Objective To investigate the infection of Leptospira in the main host animals and local residents in Baiquan Town, Dinghai District, Zhoushan, Zhejiang Province, China, and assess the potential epidemic risk of leptospirosis, so as to provide a basis for the prevention and control of leptospirosis in Zhoushan islands. Methods Ecological surveillance of host animals was conducted using night clamping and cage trapping methods and kidney samples were collected. The host animals were identified and analyzed for population density and species composition. Quantitative reverse transcription PCR was used to detect the nucleic acids of Leptospira in host kidney and human serum samples. Positive samples were subjected to reverse transcription PCR targeting the 23S rRNA gene for amplification and sequencing to conduct genotyping and homology analysis. ELISA was used to detect IgM and IgG antibodies of Leptospira in human serum. Chi-square test or Fisher's exact test was used to analyze differences between groups. Results In 2023, a total of 234 main hosts (small mammals) were captured in Baiquan Town, with a density of 7.50% capture rate and a dominant species of Rattus norvegicus (74.07%). The kidney tissues of 59 small mammals were positive for Leptospira nucleic acids, with a positive rate of 25.21%. The kidney tissues of 19 samples were successfully sequenced for 23S rRNA gene, with 13 L.borgpetersenii and 6 L.interrogans. None of the 516 human serum samples were positive for Leptospira nucleic acids, 33 (6.40%) samples were positive for IgG, and 12 samples (2.33%) were positive for IgM. Conclusions Baiquan Town is characterized by high density of main host animals, high Leptospira infection rate, and low population immunity rate. In addition, Baiquan Town has a subtropical monsoon climate with heavy rainfall in August, and the potential risk of leptospirosis epidemics is high.
  • Survey of animal-borne pathogens among companion animals of cats and dogs kept in households in a district of Beijing, China
    GAO Xiang, TIAN Ji-jing, ZHANG Wei-wei, ZHANG Long-fei, ZHAO Hong-qing
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 740-743. https://doi.org/10.11853/j.issn.1003.8280.2024.06.021
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    Objective To investigate Rickettsia, Bartonella, and other major animal- and insect-borne pathogens carried by companion animals such as cats and dogs kept in households in Fengtai District, Beijing, China. Methods Anticoagulant whole blood from cats and dogs were collected at pet hospitals in Fengtai District, Beijing, and related epidemiological information was recorded. DNA was extracted from whole blood, and Rickettsia, Anaplasmataceae, Bartonella, Coxiella, Babesia, and Theileria were detected using nested PCR or semi-nested PCR. Results A total of 95 blood samples were collected from cats and dogs, including 33 samples from cats and 62 samples from dogs. There were 40 samples from the animals without symptoms of infection, 54 samples from those with suspected symptoms of infection, and 1 sample without records of symptoms. All samples tested negative for the above pathogens. Conclusions In this survey conducted in Fengtai District, Beijing, no Rickettsia, Bartonella, Coxiella, or Babesia pathogens were found in cats and dogs collected, or the pathogen load in the blood was too low to be detected, indicating a low risk of carrying and transmitting animal-borne pathogens among household companion animals such as cats and dogs. However, due to the limited sample size and the singularity of the sampling site, further research is needed to confirm this conclusion.
    • Review
  • Research progress on the epidemic characteristics and virus genotypes of Japanese encephalitis in China
    YAN Wen-zhe, LI Jin-yu, GUO Yu-hong, YUE Yu-juan, LIU Xiao-bo, SONG Xiu-ping, LU Liang, ZHAO Ning
    Chinese Journal of Vector Biology and Control. 2024, 35(6): 744-752. https://doi.org/10.11853/j.issn.1003.8280.2024.06.022
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    Japanese encephalitis virus (JEV) is an important arbovirus that continues to spread in China. Japanese encephalitis (JE) caused by JEV is one of the important public health problems in China. Over the years, despite significant control of JE in China, the geographical distribution of JE cases and the age structure of the affected population have changed due to ecological changes and vaccination. Moreover, JEV has evolved rapidly, and the dominant genotype has changed from GⅢ to GⅠ,which brings challenges to the prevention and control of JE. This paper reviewed the epidemic characteristics of JE and the genotypes of JEV in China, providing reference for the prevention and control of JE.
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