20 October 2024, Volume 35 Issue 5
    

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    Experimental Study
  • Palatability of different rodenticide baits at large construction sites in the eastern coastal area of Shanghai, China
    FENG Lei, LU Li-hua, YUAN Yong-ting, YU Si-yu, LIU Han-zhao
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 513-516. https://doi.org/10.11853/j.issn.1003.8280.2024.05.001
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    Objective To select palatable rodenticide baits, so as to provide support for reducing time invested and improving rodent control quality in large-scale rodent control activities. Methods Wax block baits, rice baits, corn baits, wheat baits, and peanut baits containing 0.005% brodifacoum were each paired up with a type of bait base (naturally dried peanuts) in a 1∶1 ratio. The baits were placed in a saturated manner. Bait consumption was monitored and recorded consecutively for seven consecutive days. Analysis of variance and bivariate correlation analysis were performed. Results The 7-day cumulative feeding coefficient (FC) was 0.57 for the peanut baits, indicating good palatability; 0.18 for the rice baits, 0.18 for the wax blocks, and 0.17 for the corn baits, indicating moderate palatability; and 0.10 for the wheat baits, indicating poor palatability. There were significant differences in the 7-day cumulative FC of different baits in paddy field (F=25.340, P<0.001), residential area (F=5.667, P=0.002) and forest habitat (F=3.190, P=0.022), and the 7-day cumulative FC of peanut bait was the highest in the three habitats, which was 0.69, 0.54 and 0.49, respectively. The corn baits also showed good palatability in residential areas with a 7-day cumulative FC of 0.41. Conclusion Before starting construction at construction sites in the eastern coastal area of Shanghai, China, peanut baits containing brodifacoum can be used for large-scale rodent control work, which can improve the efficiency of rodent control.
  • Selection and identification of deltamethrin-degrading bacteria
    ZHOU Qiu-ming, NAN Chun-yan, YUAN Hao, SHAN Wen-qi, TAO Feng, DONG Hao-wei, PENG Heng, MA Ya-jun
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 517-522. https://doi.org/10.11853/j.issn.1003.8280.2024.05.002
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    Objective To select and identify deltamethrin-degrading bacteria in paddy fields, and to determine their degradation efficiency. Methods A bacterial flora capable of degrading deltamethrin was obtained through domestication, enrichment, isolation, and purification. The species was identified based on morphological and molecular characteristics. For single colonies, the full length of the 16S rRNA gene was sequenced and analyzed, and for the flora, the 16S rRNA V4 region was sequenced using the MiSeq high-throughput method. Sequence annotation and analysis were conducted. Bacterial composition and abundance were described at species and genus levels. The flora was cultured with deltamethrin, bifenthrin, and cyhalothrin separately, and the degrading efficiency was calculated based on the residual concentrations of the insecticides. Results A bacterial flora capable of degrading deltamethrin was obtained from the water of paddy fields. The identified single colonies included Amycolatopsis eurytherma, Acinetobacter baumannii, Ancylobacter sp., Rhodococcus spp., Amycolatopsis spp., Ochrobactrum sp., and Xanthobacter sp. The MiSeq high-throughput sequencing results showed that bacteria >4% in abundance at the genus level included Pseudomonas （26.78%）, Acinetobacter （7.00%）, Ochrobactrum （6.82%）, Achromobacter （5.00%）, Klebsiella（4.39%）, Microbacterium（4.12%）. The degradation rates of the three pyrethroid insecticides by the bacterial flora continued to increase since day 2, peaking on day 8 the longest observation period at 76.75% （bifenthrin）, 63.65% （deltamethrin）, and 74.20% （cyhalothrin； reaching the plateau on day 6）. Conclusions A deltamethrin-degrading bacterial flora was successfully obtained, in which Pseudomonas was the dominant population, showing wide degradation efficiency for pyrethroid insecticides. This study provides basic data for the field application of degrading bacteria and the studies about rapid degradation of insecticides.
    • Vector Surveillance
  • Resistance of Blattella germanica to five insecticides in Zhejiang Province, China, 2017-2022
    WANG Jin-na, LIU Qin-mei, WU Yu-yan, LUO Ming-yu, LI Tian-qi, GONG Zhen-yu, SUN Ji-min
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 523-528. https://doi.org/10.11853/j.issn.1003.8280.2024.05.003
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    Objective To investigate the resistance levels of Blattella germanica to five commonly used insecticides in Zhejiang Province, China, so as to provide a basis for rational use of insecticides and scientific control of cockroaches. Methods From 2017 to 2022, field population of B. germanica were collected in different surveillance areas of Zhejiang Province in different years. The resistance of B. germanica to beta-cypermethrin, deltamethrin, acephate, dichlorvos, and propoxur was measured by using the residual film method with a conical flask. The median knockdown time and resistance ratio (RR) were calculated using a probit regression model. Results From 2017 to 2022, the overall resistance of B. germanica to pyrethroid insecticides was relatively high in Zhejiang Province. The RR for beta-cypermethrin was 11.49 in Jinhua in 2022, 6.48 in Shaoxing in 2021, 16.00 in Wenzhou in 2018, and 6.87 in Lishui in 2018, indicating medium-to-high resistance levels. The RR for deltamethrin was 8.66 in Quzhou in 2020, 10.20 in Wenzhou in 2017, 11.66 in Jinhua in 2018, and 7.58 in Lishui in 2018, showing medium-to-high resistance levels. The RR for dichlorvos was 7.86 in Jinhua in 2022, 7.33 in Shaoxing in 2021, and 7.05 in Wenzhou in 2017, showing medium resistance levels. In general, B. germanica was sensitive or lowly resistant to acephate and propoxur in Zhejiang Province. B. germanica developed from sensitive to lowly resistant to propoxur in Ningbo since 2020, developed moderately resistant to deltamethrin in Quzhou since 2020, and developed from sensitive to moderately or lowly resistant to both pyrethroids and dichlorvos from 2018 to 2021. In 2022, insecticide resistance levels were higher in Jinhua, with high resistance to beta-cypermethrin, medium resistance to deltamethrin (RR=8.87) and dichlorvos (RR=7.86), and low resistance to propoxur (RR=2.36) and acephate (RR=1.16). Conclusions B. germanica cockroaches in Zhejiang Province are highly resistant to pyrethroid insecticides, with certain resistance to other insecticides. Future control strategies should choose appropriate insecticides according to the resistance of B. germanica.
  • A report on vector emergency surveillance in flood-stricken areas of Hebei Province, China, 2023
    MA Li-hua, ZHAO Yong, GAO Wen, HAN Xiao-li, SONG Ji-wen, SHI Jian, LIU Xu-yang, XIA Hong-wei, XUE Wei-cong, ZHANG Xiao-lei, ZHENG Yan, ZHANG Jian-zhi, ZHANG Fei-yang
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 529-537. https://doi.org/10.11853/j.issn.1003.8280.2024.05.004
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    Objective To investigate vector density changes in the flood-stricken areas of Hebei Province, China, so as to provide a basis for vector control and the prevention and control of vector-borne diseases in a scientific and orderly manner. Methods The daily monitoring data on the density of mosquitoes, flies, and rodents were collected at 192 resettlement sites in 21 counties/cities/districts of 7 flood-stricken prefecture-level cities in Hebei Province from August to October 2023. The density of mosquitoes and flies was monitored through visual inspection, and the density of rodents was measured using the footprint tracking method. R 4.2.2 software was used to perform the Wilcoxon signed-rank test, Friedman test, and Pearson correlation analysis. Results The average densities of mosquitoes, flies, and rodents of all the resettlement sites were 1.05 inds/labor hour, 0.45 inds/m2, and 0.037 tracks/2 000 m, respectively. The average mosquito density of the resettlement sites showed a slowly fluctuating downward trend, with the highest level on the 1st day of surveillance, reaching 1.97 inds/labor hour, which was lower than the reference level for mosquito control (10 inds/labor hour). The density of flies showed a slowly fluctuating downward trend, with the higher levels on the 1st day (0.71 inds/m2) and the 25th day (1.00 inds/m2) of surveillance, approximating or reaching the reference level for fly control (1 ind/m2). The average rodent density showed a rapidly downward trend, with the peak on the 1 st day at 0.181 tracks/2 000 m, far lower than the rodent control reference level (5 tracks/2 000 m). Pest and rodent control work was completed for a total of 12 586 points covering 1 353 104 m2 of three types of habitats, including resettlement sites and their surroundings, toilets, and garbage points. In August 2023, there were 729 cases of vector-borne diseases in the flood-stricken areas, which were more than the cases in the same period of 2022 (t=-1.429, P=0.002) and 2021 (t=-0.929, P=0.119), similar to the number in the same period of 2020 (t=-0.024, P=1.000), and more than the number in September 2023, the late stage of the flood disaster (W=44.500, P=0.013). From August to September 2023, the local reported no case of mosquito-borne infectious diseases, 1 case of rodent-borne typhus, and 1 215 cases of fly-related diseases (can be mechanically carried and transmitted by flies) diseases such as the other infectious diarrhea and bacillary dysentery; and the number of daily cases was not correlated with the density of flies (r=-0.195, P=0.146). Conclusions The density of mosquitoes, flies, and rodents was low at the resettlement sites of flood-stricken areas in Hebei Province in 2023. When the density exceeded the vector and rodent control reference levels, the implementation of emergency vector and rodent control effectively limited the density of vectors and rodents in the flood-stricken areas and prevented the outbreak of the related diseases.
  • An analysis of surveillance results of Culex pipiens pallens/quinquefasciatus in Changsha,Hunan Province,China,2017-2022
    LIN Bin, CHEN Jian-yong, PENG Lai, ZHU Cai-ying, XIAO Shan
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 538-542. https://doi.org/10.11853/j.issn.1003.8280.2024.05.005
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    Objective To analyze the seasonal fluctuation and distribution in different habitats of Culex pipiens pallens/quinquefasciatus in Changsha, Hunan Province, China from 2017 to 2022, so as to provide a scientific basis for the control of Cx. pipiens pallens/quinquefasciatus and mosquito-borne infectious diseases in Changsha. Methods According to the National Vector Surveillance Program, Cx. pipiens pallens/quinquefasciatus mosquitoes were obtained using the light trap method in urban residential areas, parks, hospitals, residential houses, and pig pens from April to November of 2017 to 2022. The mosquito population density, seasonal fluctuation, and distribution were analyzed. The mosquito density of different years was compared through analysis of variance (ANOVA) with a completely randomized design, and mosquito density in different months and different habitats was analyzed by two-way ANOVA. Results The mean annual density of Cx. pipiens pallens/quinquefasciatus in Changsha from 2017 to 2022 was 17.83 mosquitoes/light·night. Throughout a year,mosquito density showed a bimodal distribution,peaking in May-June and September. Density differed significantly in different months (F=15.921, P<0.001),which was highest in May (38.92 mosquitoes/light·night) and June (40.42 mosquitoes/light·night). The mosquito densities of different habitats were also significantly different (F=36.014,P<0.001),with the highest levels in pig pens (40.06 mosquitoes/light·night) and residential houses (30.23 mosquitoes/light·night). There was interaction between "month" and "habitat" (F=5.563, P<0.001). Conclusions The peak activeity of Cx. pipiens pallens/quinquefasciatus is in May and June, and the density in pig pens and residential house is high. Specific control programs should be development depending on habitat and season, and mosquito control should be strengthened in rural areas in May and June.
  • An analysis of surveillance results of dengue vector Aedes larvae in Shanxi Province, China, 2015-2021
    ZHAO Jun-ying, DAI Pei-fang, LIU Li-ying, TIAN Xiao-dong, CUI Shuang-jie, YAN Chang-fu
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 543-546. https://doi.org/10.11853/j.issn.1003.8280.2024.05.006
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    Objective To analyze the monitoring data on the dengue vector Aedes albopictus and find out the breeding environment of Aedes mesquito in Shanxi Province, China, so as to provide a scientific basis for the risk assessment, prediction and early warning, and prevention and control of dengue fever. Methods Ecological data of dengue vector Ae. albopictus were collected from five surveillance sites in Shanxi Province from June to September of 2015 to 2021. The Breteau index (BI), container index (CI), and house index (HI) were used for analysis. Chi-square test and analysis of variance were used to compare mosquito seasonality, the type of standing water, and mosquito breeding site at the five surveillance sites in different years. Results For Ae. albopictus in Shanxi Province from 2015 to 2021, the total BI was 4.48, CI was 3.30, and HI was 4.24. There was no significant difference in the BI values of different years (F=0.613, P=0.719). There were significant differences in CI (χ2=21.218, P=0.002) and HI (χ2=72.243, P<0.001) among different years. Among stagnant water types, the number of unused containers (bowls, bottles, tanks, and jars) was the largest, accounting for 41.18%. By monitored habitat, the mean annual BI of waste tires was highest (13.37), and by breeding site, the positive rate of tires/waste tires was highest (5.64%). The density of Ae. albopictus mainly peaked in July to August, with the highest BI being 15.35 in Yaodu District in August. Conclusion It is necessary to strengthen the management of waste tires and water containers, especially in July and August, and knowledge popularization about mosquito prevention and control, so as to prevent the local transmission of dengue fever.
    • Vector-borne Disease
  • Relationship between serum parameters and the severity of hemorrhagic fever with renal syndrome
    DENG Le, ZHONG Hui-hai
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 547-551. https://doi.org/10.11853/j.issn.1003.8280.2024.05.007
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    Objective To investigate the value of serum procalcitonin (PCT) and albumin (ALB) in predicting the severity of hemorrhagic fever with renal syndrome (HFRS). Methods A retrospective analysis was performed on the clinical and laboratory data of 21 adult patients with HFRS, involving white blood cells (WBC), platelets (PLT), PCT, ALB, and activated partial thromboplastin time (APTT). The t-test or Mann-Whitney U test was used to compare the differences in the levels of WBC, PLT, PCT, ALB and APTT in different disease severity groups. Spearman rank correlation (for skewed distribution data), Pearson correlation (for normal distribution data), binary logistic regression were used to analyze the statistical power of PCT and ALB in predicting the severity of HFRS. Results Compared with those in the mild group, the levels of WBC, PCT, and ALB in the severe group were significantly higher (all P<0.05), with no significant differences in the levels of PLT and APTT between the two groups (both P>0.05). The disease severity was positively correlated with WBC (r=0.471, P=0.031) and PCT (rs=0.819, P<0.001) and negatively correlated with ALB (rs=-0.801, P<0.001). There were no significant correlations between PLT and the severity of the disease, and between APTT and the severity (both P>0.05). In the severe group, PCT and ALB levels were independently correlated with the disease severity [OR=7.812,95% confidence interval (CI ): 1.579-38.655, P=0.012; OR=0.713,95% CI : 0.546-0.932, P=0.013]. Conclusion Serum PCT and ALB levels are independent risk factors reflecting the severity of HFRS, showing high clinical value as early warning parameters to assess the severity of HFRS.
  • Epidemiological characteristics and spatial clustering patterns of scrub typhus in Xuzhou, Jiangsu Province, China, 2013-2022
    ZHOU Qiang, MIAO Yu-yang, ZHANG Wen
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 552-556. https://doi.org/10.11853/j.issn.1003.8280.2024.05.008
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    Objective To analyze the epidemiological characteristics and spatial distribution of scrub typhus in Xuzhou, Jiangsu Province, China, so as to provide a theoretical basis for formulating scientific and effective prevention and control strategies and measures. Methods Based on the data on reported scrub typhus cases and population data from the China Information System for Disease Control and Prevention, the incidence and trend of scrub typhus were described in Xuzhou from 2013 to 2022 by using descriptive epidemiological methods; the peak season and time of scrub typhus were determined by using the concentration method and circular distribution method; the regional distribution of scrub typhus was visualized with the use of ArcGIS 10.3 software; and spatial autocorrelation analysis was conducted with the use of GeoDa 1.14 software. Results A total of 259 cases of scrub typhus were reported in Xuzhou from 2013 to 2022, with an average annual reported incidence rate of 0.30/100 000. By occupation, the patients were mainly farmers (230/259, 88.80%), followed by homemakers and the unemployed (8/259, 3.09%), and workers (6/259, 2.32%). By age, the reported cases were mainly concentrated in the age group of 40 to <80 years (225/259, 86.87%), most common in the age group of 60 to <70 years (80/259, 30.89%). Remarkable seasonality was observed in the incidence of scrub typhus, which was higher during October to November of each year (243/259, 93.82%). The circular distribution model suggested that November 2 was the peak day of the incidence of scrub typhus, with the peak period lasting from October 10 to November 25. The global autocorrelation Moran's I of the annual average incidence rate was >0 (P<0.05), and the local autocorrelation results indicated Pizhou as a "high-high" cluster area and Suining County as a "high-low" cluster area. Conclusions The incidence of scrub typhus shows stringent seasonality in Xuzhou, which is an autumn-type epidemic area. The reported incidence rate of scrub typhus shows an overall upward trend with age, and the reported incidence is mainly concentrated in three eastern areas of Xuzhou. It is necessary to timely carry out health education for key populations and vector control in key areas.
  • Epidemiological analysis of severe fever with thrombocytopenia syndrome in Dandong, Liaoning Province, China, 2011-2023
    YU Dan-mei, PANG Ya-nan
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 557-563. https://doi.org/10.11853/j.issn.1003.8280.2024.05.009
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    Objective To analyze the population, temporal, and spatial characteristics of the reported cases of severe fever with thrombocytopenia syndrome (SFTS) in Dandong, Liaoning Province, China, 2011-2023, so as to provide evidence for formulating SFTS prevention and control measures. Methods Excel 2007 software was used to establish a database. SPSS 23.0 software was used to conduct descriptive analysis on the population, time, and regional characteristics of SFTS. Rate or percentage was used to describe count data. The comparison of rates was conducted using Chi-square test. Joinpoint Regression 5.0 software was used to analyze the changes in incidence rate based on the Joinpoint Regression Program. Results From 2011 to 2023, a total of 558 cases of SFTS were reported in Dandong, with an average annual incidence of 1.83/100 000. The annual incidence increased, slightly decreased, and then increased, showing an overall increasing trend (χ2trend=51.489, P<0.001). The male-to-female ratio of the cases was 1.17:1. The cases mainly occurred in individuals with 45-<80 years of age (87.10%). In terms of occupation, the disease mainly affected farmers (66.85%). The incidence of SFTS showed obvious seasonality, with the reported cases mainly distributed from May to October, and the incidence peaked from July to September. The top two counties, county-level cities, and districts in terms of reported cases and average annual incidence were all Kuandian County (256 cases, 4.70/100 000) and Fengcheng City (201 cases, 2.78/100 000). The top five townships in terms of cumulative number of reported cases were Kuandian Town in Kuandian County, Bianmen Town in Fengcheng City, Maodianzi Town in Kuandian County, Shicheng Town in Fengcheng City, and Guanshui Town in Kuandian County. The top five townships in terms of average annual incidence were Maodianzi Town in Kuandian County, Dachuantou Town in Kuandian County, Yangmuchuan Town in Kuandian County, Hushan Town in Kuandian County, and Shicheng Town in Fengcheng City. Conclusions The incidence of SFTS in Dandong increased and showed obvious seasonal and regional distribution. The distribution of cases showed a trend of spreading from the middle and low mountain areas in the north of Dandong to the central hilly area and the central and southern plain areas. Middle-aged and elderly farmers were the primary affected populations. Significant emphasis should be placed on the prevention and control of SFTS. Comprehensive measures should be taken to control the SFTS epidemic in high-incidence areas.
    • Technology and Method
  • Nucleic acid-based method for detection of insecticide resistance-associated mutations in carboxylesterase MdαE7 （G137D） and acetylcholinesterase （V260L and F407Y） of Musca domestica
    LIU Juan, LIU Peng, WANG Ya-wei, YU Xiao-mei, LI Xue-mei, QIU Xing-hui
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 564-568. https://doi.org/10.11853/j.issn.1003.8280.2024.05.010
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    Objective To establish a molecular method for detection of resistance-conferring mutations in carboxylesterase MdαE7 (G137D) and acetylcholinesterase (V260L and F407Y) of Musca domestica by adopting the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) strategy. Methods Fly traps or capture nets were used to collect adult houseflies from June to July 2022 in five counties, county-level cities, or districts, i.e., Zizhong, Weiyuan, Longchang, Shizhong, and Dongxing in Neijiang City, Sichuan Province, China. The houseflies were preserved in absolute ethanol and brought back to the laboratory for processing. DNA fragments of M.domestica acetylcholinesterase-encoding gene and MdαE7 gene were amplified by polymerase chain reaction (PCR) using gene-specific primers and individual genomic DNA as the template. Gene fragments were amplified by polymerase chain reaction (PCR) using individual genomic DNA as the template. The PCR products were digested using specific restriction endonucleases. The genotype of individual houseflies was determined according to the restriction fragment length polymorphisms of digestion products via agarose gel electrophoresis. Results Using gene-specific primers, the PCR products, MdαE7-137 (213 bp), AChE-260 (170 bp), and AChE-407 (133 bp), were obtained. After MdαE7-137 was incubated with Bst XI, the wild homozygote (GG), resistant homozygote (DD) and heterozygote (G/D) could produce two bands ( 26 and 187 bp), a band (213 bp), and three bands (26, 187, and 213 bp), respectively. After AChE-260 was treated with Sal I-HF®, a band (170 bp), two bands (26 and 144 bp), and three bands (26, 144, and 170 bp) could be seen on gel for wild homozygote (VV), resistant homozygote (LL) and heterozygote (V/L) respectively. The presence of one band (133 bp), two bands (31 and 102 bp) and three bands (31, 102, and 133 bp) on the gel loaded with Eco RV-HF® digestion products of AChE-407 was scored as wild homozygote (FF), resistant homozygote (YY), and heterozygote (F/Y) respectively. Conclusions The established PCR-RFLP genotyping method is simple and highly accurate. This method can be used for rapid determination of the frequencies of the resistance-related mutations G137D in carboxylesterase MdαE7 and V260L and F407Y in AChE in field M.domestica populations.
  • Species composition and distribution of mosquito in residential areas of the Yuanjiang River-Red River basin in Yunnan Province,China
    GUO Xiao-lian, LUO Chun-hai, WU Lin-bo, WEI Chun, YANG Rui, ZHOU Shi-sheng, WANG Bin, WAN Quan, HE De-gao, ZHOU Hong-ning, YANG Kun
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 569-575. https://doi.org/10.11853/j.issn.1003.8280.2024.05.011
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    Objective To investigate the species and distribution of mosquitoes in the residential areas of the Yuanjiang River-Red River basin, Yunnan Province, China, and to analyze their species composition and distribution characteristics, so as to provide reference data for the prevention and control of mosquito-borne diseases in this region. Methods During July to August in 2022 and June in 2023, mosquitoes were collected using light traps at night in nine rural residential areas selected from five counties/cities located in the upstream, midstream,and downstream areas of the Yuanjiang River-Red River basin. Excel 2013 software was used for data pooling and analysis. The Berger-Parker index (I) was calculated to determine the dominant mosquito species. The Kruskal-Wallis H test was used to compare the densities of mosquitoes in different regions. Spearman's rank correlation analysis was performed to analyze the correlation between latitude and the richness and density of mosquitoes. Results A total of 76 710 female mosquitoes belonging to 29 species in 7 genera under 2 subfamilies were captured in the two field surveys. Culex tritaeniorhynchus (I=0.73) and Anopheles sinensis (I=0.21) were the dominant mosquito species in the basin. Among all the mosquito species, the density of Cx. tritaeniorhynchus was highest at 430.57 mosquitoes/night·lamp, followed by An. sinensis at 126.79 mosquitoes/night·lamp. There was no significant difference in mosquito density between different regions (H=3.773, P=0.152). With the decrease in latitude from the north to south of the basin, increasing trends were observed for mosquito species richness (rs=-0.678, P=0.045) and density (rs=-0.745, P=0.021). Conclusion The densities of Cx. tritaeniorhynchus and An. sinensis are high in the Yuanjiang River-Red River basin,where health departments should strengthen the surveillance of mosquito density and cases of Japanese encephalitis.
    • Investigation
  • Resistance of Musca domestica to beta-cypermethrin, deltamethrin, and propoxur in Shizuishan, Ningxia Hui Autonomous Region, China in 2020 and 2023
    NIU Ming-jie, ZHAO Xiu-yun, QIN Mei, HE Guang-zhong, CHEN Yue, YANG Huan
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 576-580. https://doi.org/10.11853/j.issn.1003.8280.2024.05.012
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    Objective To investigate the resistance of Musca domestica to three commonly used insecticides and the changes in Shizuishan, Ningxia Hui Autonomous Region, China, and analyze the reasons, so as to provide a basis for the development of scientific, rational, and effective fly control measures. Methods The topical application method was used to determine the resistance levels of M. domestica to insecticides in 2020 and 2023. The median lethal dose (LD50), regression equation, and resistance ratio were calculated with the use of DPS 18.10 software, and were compared with the resistance data of 2016. The information on the usage of insecticides (retail and centralized procurement) in Shizuishan in 2019, 2021, and 2022 was obtained through on-the-spot inspection and enquiry, and descriptive analysis was performed on the data. Results The resistance ratios of M. demestica to beta-cypermethrin, deltamethrin, and propoxur in Shizuishan were 24.70, 144.72, and 2.66 in 2020, respectively, and the resistance ratios were 37.65, 25.89, and 6.07 in 2023, respectively. In 2016, 2020 and 2023, M. domestica was lowly resistant to propoxur and highly resistant to beta-cypermethrin and deltamethrin; and the resistance ratio for beta-cypermethrin showed an increasing trend, while the resistance ratios for deltamethrin and propoxur showed decreasing trends. From 2019 to 2022, a total of 16 kinds of insecticides were used in Shizuishan, and pyrethroids were most common, which accounted for 66.66%, 41.67%, and 42.86% of all the insecticide types used in 2019, 2021, and 2022, respectively; and the annual consumption of pyrethroids was highest, accounting for 82.31%, 36.36%, and 59.08% of the total consumption in the three years, respectively. Conclusions M. domestica in Shizuishan has developed different levels of resistance to beta-cypermethrin, deltamethrin, and propoxur, which is consistent with local use of the three insecticides. The three insecticides should be used in a rotational way with other insecticides without cross-resistance, so as to delay the development of the resistance of M. domestica.
  • Review results of malaria samples by Liaoning provincial malaria diagnostic reference laboratories in Liaoning Province, 2015-2021
    WANG Bo, SUN Ying-wei, LI Xin, WANG Zi-jiang, YU Wei-jun, LEI Lu, YU Wei, MAO Ling-ling
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 581-586. https://doi.org/10.11853/j.issn.1003.8280.2024.05.013
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    Objective To assess the diagnostic capacities for malaria of prefecture-level malaria diagnostic reference laboratories of Liaoning Province, China by checking the samples from malaria cases provided by each city from 2015 to 2021 at the provincial reference laboratory, so as to provide a basis for further improving the malaria diagnostic capacity of the centers for disease control and prevention in each city. Methods The blood smear samples were checked under a microscope, and the anticoagulated blood samples from malaria cases were tested using nested PCR and quantitative real time PCR. The Chi-square test and Fisher's exact test were used to compare the detection rate between groups, and to compare the detection rate and reported positive rate. Results A total of 380 samples from malaria cases were checked from 2015 to 2021, in which 270 were positive for Plasmodium falciparum, 20 were positive for P. vivax, 11 were positive for P. malariae, 34 were positive for P. ovale, and 45 were negative. The samples were mainly from Shenyang and Dalian, with a total of 278 samples, accounting for 73.16% of all the samples of the province. The check results showed that the coincidence rate was 95.36% for Shenyang and 92.97% for Dalian, and the average coincidence rate of all the laboratories was 90.13%. The positive rate by nested PCR was 87.63%, and the positive rate by blood smear microscopy was 74.47%, which were significantly different (χ2=46.296, P<0.001). Conclusions Although progress has been made in the capabilities of blood microscopy and nucleic acid detection of prefecture-level centers for disease control and prevention of Liaoning Province, their detection levels are imbalanced, and there is still a large room for improvement. In order to consolidate the malaria elimination achievements, it is necessary to continue to strengthen laboratory personnel training on testing ability, stabilize the testing level, and make sure timely and accurate detection and feedback.
  • An investigation of Anaplasma phagocytophilum carried by Haemaphysalis longicornis in Yantai, Shandong Province, China
    ZHAO Ying-zhu, LI Chun-hui, LIU Cheng-juan, WANG Ting, ZHANG Hui-min, XIAO Long-jie, WANG Xue-jun, GUO Pei-jun
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 587-592. https://doi.org/10.11853/j.issn.1003.8280.2024.05.014
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    Objective To investigate the prevalence of Anaplasma phagocytophilum in Haemaphysalis longicornis in Yantai, Shandong Province, China, so as to provide a scientific basis for the prevention and control of human granulocytic anaplasmosis and the dangers of ticks in Yantai. Methods Tick surveillance was carried out in Muping District, Yantai economic and technological development zone (development zone), Penglai District, Haiyang City, Qixia City, Zhaoyuan City, and Laizhou City of Yantai from April to October in 2021. On-host ticks were collected from domestic animals through body surface inspection and questing ticks in the field environment were collected using the flagging method. Nested PCR was used to detect A. phagocytophilum in H. longicornis specimens. SPSS 22.0 software was used to perform the Chi-square test to compare the positive rates of different groups. Results A total of 1 698 ticks (1 097 on-host ticks and 601 questing ticks) were captured, all belonging to H. longicornis. DNA was extracted from 913 ticks grouped by region, source, developmental stage, and whether they were engorged. Among the obtained 413 DNA samples, 13 were positive for the nucleic acid of A. phagocytophilum, with a positive rate of 3.15% and a minimum infection rate of 1.42%; and of the 13 positive samples, 11 were from adult on-host ticks (2 from dogs and 9 from sheep), and the other 2 were from questing ticks (1 from larvae and 1 from adults). There was no significant difference in the positive rates of ticks from different hosts (χ2=1.722, P=0.423). By region, 3 and 6 positive samples were detected in the on-host ticks in the development zone and Laizhou City, 1 positive sample was detected in the free ticks in Penglai District, and 3 positive samples （2 from on-host ticks and 1 from free ticks） were detected in Zhaoyuan City. There was a significant difference in the positive rates of ticks from different regions （χ2=11.468, P=0.038）. Conclusions H. longicornis, the dominant tick species in Yantai, from different host sources in various districts/cities have an infection with A. phagocytophilum, indicating a high pathogenic risk from human granulocytic anaplasmosis. Tick surveillance and pathogen detection should be strengthened to inform the prevention and control of human granulocytic anaplasmosis.
  • Investigation of soil metal content in plague natural foci with Meriones unguiculatus as the host in Ordos Plateau, Inner Mongolia, China
    ZHANG Jiao, LI Jian-yun, LIU Fang, ZHANG Zhe, LIU Yang, GUO Wen-xiu
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 593-597. https://doi.org/10.11853/j.issn.1003.8280.2024.05.015
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    Objective To measure soil metal content in plague natural foci with Meriones unguiculatus as the host in the Ordos Plateau, Inner Mongolia, China and to investigate their correlations. Methods Soil samples were collected from 30 sites with and 30 sites without plague natural foci in the Ordos Plateau. X-ray fluorescence spectrometry was used to measure the content of 13 metal elements such as potassium, iron, and calcium in soil. Data were entered and organized using Excel 2019 software. SPSS 26.0 software was used for independent samples t-test and Mann-Whitney U test to analyze the differences in metal content between the two groups of sampling. Spearman rank correlation analysis was used to determine the correlations between the content of metal elements. Results Calcium was the most abundant metal element in the soils from both groups of sampling sites in the Ordos Plateau, followed by iron and potassium. The differences in potassium, iron, and rubidium content between the soils from the two groups of sampling sites were statistically significant (Z=-2.423, P=0.015; Z=-2.034, P=0.042; t=2.860, P=0.005). Positive correlations were found between the content of most metal elements in both groups of sampling sites, such as potassium and lead, calcium and iron, and iron and lead (all P<0.05). Conclusions The soil from the plague natural focus with Meriones unguiculatus as the host in the Ordos Plateau is rich in calcium, iron, and potassium. There are correlations between most of the metal elements in the sampling sites with and without plague natural foci. The role of metal elements in plague epidemic warrants further study.
  • An analysis of dengue fever outbreak characteristics in four cities/counties of Yunnan Province, China, 2023
    ZHANG Rong-bing, DUAN Jing, CHEN Li-hua, HAO Lin-hui, TIAN Rong, YANG Qian, YE Qing
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 598-603. https://doi.org/10.11853/j.issn.1003.8280.2024.05.016
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    Objective To investigate the characteristics of dengue fever outbreaks in four cities/counties of Yunnan Province, China, and to provide a reference for the prevention and control of dengue fever. Methods The data about dengue fever cases reported in Yunnan Province in 2023 were collected from the China Information System for Disease Control and Prevention. The circular distribution method was used to analyze the temporal patterns of dengue fever outbreaks in Gengma Dai and Wa Autonomous County, Jinghong City, Ruili City, and Mengla County. Excel 2010 software was used for data collation, and SPSS 19.0 software was used for data analysis. The rate or constituent ratio was compared using the Chi-square test. The correlation of non-normally distributed continuous data was examined through Spearman correlation analysis. Descriptive epidemiological method was used to describe the characteristics of dengue fever outbreaks in the four cities/counties. Results A total of 13 748 cases of dengue fever were reported in Yunnan Province in 2023, with a reported incidence rate of 29.42/100 000. The four cities/counties reported a total of 10 012 cases of dengue fever, accounting for 72.83% (10 012/13 748) of the total number in the province. The peak period was from June 15 to November 11, and the peak day was August 30. The temporal distributions of the imported cases, local cases, and exported cases in the four cities/counties were generally consistent, and they were correlated in different months (rsimported-local=0.901, P=0.006; rslocal-exported=0.893, P=0.007; rsimported-exported=0.793, P=0.033). In terms of the reported cases distribution, the top five occupations were farmers, homemakers and the unemployed, business employees, freelancers, and students, accounting for 31.25% (2 795/8 945), 16.88% (1 510/8 945), 14.21% (1 271/8 945), 10.90% (975/8 945), and 8.09% (724/8 945), respectively. By age distribution, the group of 20 to <70 years accounted for 80.00% (7 818/9 772), with the highest reported incidence rate in the group of 70 to <80 years (1 244.41/100 000) and lowest in the group of <10 years (306.55/100 000). There was an increasing trend in the reported incidence rate with age (χ2trend=985.310, P<0.001). By regional distribution, the cases were mainly concentrated in ports or urban townships densely populated and with large numbers of floating people, which were more distributed in the border areas and scattered in the inland and suburban townships. The number of local cases reported in national port townships was largest, with an incidence rate of 1 341.09/100 000, while the lowest incidence rate was 250.60/100 000 in townships without ports or local channels. As the opening level increased, the incidence rate of local cases reported in each township tended to increase (χ2trend=4 610.937, P<0.001). The incidence rate of each township was positively correlated with the local population density (rs=0.446, P=0.006). Conclusions In the four cities/counties of Yunnan Province, dengue fever cases are mainly clustered in ports or urban townships, and show specific distribution patterns by region, population, and time. The focus should be on densely populated urban areas and port townships with large floating populations near the border, and high attention should be paid to the long-distance export of infectious sources and vectors to low-risk areas.
  • Cross-sectional analysis of distribution characteristics of lesion subtypes in cases of echinococcosis
    XUE Chui-zhao, LIU Bai-xue, WANG Xu, WU Wei-ping, ZHENG Can-jun, KUI Yan, HAN Shuai
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 604-615. https://doi.org/10.11853/j.issn.1003.8280.2024.05.017
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    Objective To investigate the distribution of the subtypes, location, and number of lesion in echinococcosis cases in China, so as to provide a theoretical basis for the diagnosis, prevention, and management of echinococcosis. Methods Cases with complete information on lesion types based on images obtained in the 2012-2016 epidemiological survey of echinococcosis in China were selected for descriptive analysis of lesion subtype distribution. Regression analysis was performed to determine the relationship between the number of lesions in each subtype and the number of cases in the corresponding subtype. Results Among the 4 014 cases included in the study, there were no significant differences between male and female patients in the proportions of cystic and alveolar echinococcosis cases in each subtype of lesion (all P>0.005). For cystic echinococcosis cases, there were significant differences in the proportion of cases among different provinces of each subtype （χ2=58.803～534.097, all P<0.05）, and there were significant differences in the proportion of cases among different occupations except for type III （subtype CL,Ⅱ,Ⅳ,Ⅴ：P<0.05 by Fisher's exact probability test; subtypeⅠ：χ2=104.534, P<0.001）. For alveolar echinococcosis cases, there were significant differences in the proportion of cases among different provinces of each subtype, i.e., infiltrative, colliquative and cavitary, calcification （all P<0.05 by Fisher's exact probability test）, and there were significant differences in the proportion of cases among different occupation of each subtype （Fisher's exact probability test： P<0.001; P=0.009; P<0.001）. Colliquative and cavitary subtype with cystic lesion as well as cystic and calcified type with alveolar lesion were not found in cases with both cystic and alveolar lesions. The proportions of cystic lesions in different stages decreased significantly in turn in Sichuan Province (Z=-2.630, P=0.009) and Xinjiang Uygur Autonomous Region (Z=-2.254, P=0.024). Not less than 90.92% of the lesions of all subtypes of cystic echinococcosis cases were located in the liver. Regression analysis showed a significant negative exponential relationship between the number of lesions of each subtype and the number of cases with the corresponding subtype lesion (all P<0.05). Conclusions There are regional and occupational characteristics in the subtype of lesions in echincoccosis cases in China, and the lesions are mainly located in the liver. The cross-sectional analysis of lesion classification can be used as an important supplement to the traditional epidemiological analysis and provide an important theoretical basis for the control, prevention, and treatment of echinococcosis.
  • An investigation of mosquito species and mosquito-borne virus in some areas of Yunnan Province, China, 2023
    ZHANG Juan, WANG Ting-ting, PU Shu-wei, FAN Zhi-hong, MAO Meng-ju, JIANG Xue-ying, LI Wen-dong, ZHOU Xiao-mei
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 616-620. https://doi.org/10.11853/j.issn.1003.8280.2024.05.018
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    Objective To investigate mosquito species and mosquito-borne viruses in some areas of Yunnan Province, China in 2023, so as to provide evidence for the prevention and control of mosquito-borne infectious diseases. Methods Mosquitoes were collected in Kaiyuan City (in Honghe Hani and Yi Autonomous Prefecture) and Huaning County and Yuanjiang Hani, Yi, and Dai Autonomous County (in Yuxi City) of Yunnan Province from July to August 2023. After species identification, the mosquitoes were examined for various viruses by quantitative PCR. The target virus gene was amplified by conventional PCR, and the virus sequences were analyzed using bioinformatics software. Results A total of 9 060 mosquitoes belonging to 5 species of 4 genera were collected, among which Culex tritaeniorhynchus was the dominant mosquito species, accounting for 50.30% of the total number of mosquitoes caught, followed by Anopheles sinensis, accounting for 33.77%, Cx. pipiens quinquefasciatus, Armigeres subalbatus and Aedes vexans were less, accounting for 5.96%,2.98% and 2.98% respectively. Ten strains of Japanese encephalitis virus were detected in mosquitoes from Kaiyuan City and Huaning County, with a positive rate of 3.31%. No other viruses were detected. According to the NS1 gene-based phylogenetic analysis and nucleotide and amino acid homology analysis of 8 strains of Japanese encephalitis virus from Kaiyuan City and Huaning County, they all belonged to Japanese encephalitis virus genotype Ⅰ. Conclusions In this investigation, Kaiyuan city and Huaning County were dominated by Cx. tritaeniorhynchus, Yuanjiang County was dominted by An. sinensis. Japanese encephalitis virus was for the first time isolated from mosquitoes in Kaiyuan City and Huaning County, indicating that the two places are epidemic areas of Japanese encephalitis, so surveillance and control should be strengthened.
  • RNA viruses carried by Rhipicephalus microplus in Yinjiang Tujia and Miao Autonomous County, Guizhou Province, China
    TANG Ji-xia, HE Xian-hai, WU Sheng-chun, MENG Jiao, CHEN Xing-xing, CHEN Qiu, LIN Zhi-jun, DAI Yi-song, WU Jia-hong, JIANG Jia-fu, SUN Yi, CAO Wu-chun, YU Fu-xun, ZHAN Lin
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 621-626. https://doi.org/10.11853/j.issn.1003.8280.2024.05.019
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    Objective To investigate tick-borne virus threats in Yinjiang Tujia and Miao Autonomous County (Yinjiang County), Guizhou Province, China. Methods Ticks were collected from the body surface of cattle in Yinjiang County. Tick species was identified by morphological characterization and 16S rDNA gene amplification. Viral metagenomic sequencing was performed on the Illumina platform. After quality control and assembly, the virus sequences were aligned with those registered in the National Center of Biotechnology Information. A phylogenetic tree was constructed for the genetic evolution characteristics of the viruses. Results A total of 23 ticks were collected in July, 2023, all of which were identified as Rhipicephalus microplus. According to metagenomic sequencing, the viruses isolated from the ticks belonged to Phenuiviridae, Rhabdoviridae, and Chuviridae and other unclassified viruses. A 5 008 bp nucleotide sequence of Lihan tick virus was assembled in this study. The sequence had the highest homology to the Lihan virus strain (ON812189) isolated from R. microplus in Chongqing in 2019, belonging to a different genetic branch from those of the Rift Valley fever virus (DQ375403) from Egypt and the Severe fever with thrombocytopenia syndrome virus (JQ733567), namely Dabie bandavirus from China. Conclusions Phenuiviridae, Rhabdoviridae, and Chuviridae viruses were found in ticks in Yinjiang County, Guizhou Province. More studies are needed to understand the pathogenicity and public health significance of these tick-borne viruses, especially the Lihan virus found in this study.
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  • A review on mouse-like animals and associated diseases in Thailand
    XU Xiang, JIANG Jin-yong
    Chinese Journal of Vector Biology and Control. 2024, 35(5): 627-632. https://doi.org/10.11853/j.issn.1003.8280.2024.05.020
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    Mouse-like animals, mostly rodents, play an important role in biodiversity indication and zoonotic disease control research, due to their large populations, wide distribution, and close relationship with the environment and natural focal diseases. With deepening communication and cooperation between Lancang-Mekong countries, the risk of rodent-borne diseases continues to rise at intra-regional and trans-regional levels. This paper aims to present the composition of mouse-like animals and associated zoonotic diseases in Thailand.
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