20 June 2024, Volume 35 Issue 3
    

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    Experimental Study
  • Gene sequence analysis of Hantavirus carried by small mammals in Anhui Province, China, 2022
    CHEN Qing-qing, HOU Yin-xu, LU Wan-hang, WU Xiao-min, WU Lei, XU Qing-hua
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 261-267. https://doi.org/10.11853/j.issn.1003.8280.2024.03.001
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    Objective To investigate Hantavirus infection and genotype characteristics in small mammals in Anhui Province, China.Methods From September 2021 to December 2022, small mammal specimens were collected in Anhui Province in accordance with the National Biovector Etiology Surveillance Program (Trial). Hantavirus nucleic acid of small mammal’s lung specimens were detected by reverse transcription real-time fluorescence quantitative PCR, and for positive samples, full-length amplification, sequencing, and sequence analysis of the S fragment were conducted.Results A total of 4 075 specimens of 8 species of samll mammals were examined in 16 cities of Anhui Province. The dominant species were Rattus norvegicus (32.15%), Mus musculus (21.87%), R. tanezumi (21.72%), and Apodemus agrarius (20.86%). The positive rate of hantaviral nucleic acids was 1.47% (60/4 075), including Hantaan virus (HNTV) and Seoul virus (SEOV). From the 60 positive samples, 19 S sequences were obtained by cross-species PCR amplification. Genetic evolution analysis showed that HNTV was H5 and SEOV was S3 subtypes, respectively. The similarity of the nucleotide sequences was 72.00% to 100% and that of amino acid sequences was 83.00% to 100%, respectively.Conclusions HNTV and SEOV infections were present in small mammals in Anhui Province. It is necessary to strengthen Hantavirus surveillance in small mammals to provide a scientific basis for the prevention and control of hemorrhagic fever with renal syndrome.
  • Cytochrome c oxidase subunit Ⅰ gene-based genetic characteristics of Rattus tanezumi in domestic rodent plague foci of Yunnan Province
    CHEN Min, SU Chao, SHI Li-yuan
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 268-273. https://doi.org/10.11853/j.issn.1003.8280.2024.03.002
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    Objective To sequence and analyze the cytochrome c oxidase subunitⅠ(COⅠ) gene of Rattus tanezumi in the domestic rodent plague foci of Yunnan Province, China, and to explore the genetic characteristics of R. tanezumi populations in different geographical areas of Yunnan Province.Methods From 2016 to 2019, R. tanezumi was captured in Dali Bai Autonomous Prefecture (Dali), Baoshan, Dehong Dai and Jingpo Autonomous Prefecture (Dehong), Lincang, Yuxi, Wenshan Zhuang and Miao Autonomous Prefecture (Wenshan), and Xishuangbanna Dai Autonomous Prefecture (Xishuangbanna). A total of 408 liver and spleen specimens of R. tanezumi were collected to extract genomic DNA and then amplify the COⅠgene by PCR. Bioinformatics methods were used for nucleotide and haplotype analysis of the COⅠ gene sequence. A molecular phylogenetic tree was constructed by using the neighbor-joining method. An analysis of molecular variance (AMOVA) among populations were performed, and gene flow and the genetic differentiation index (Fst) were caculated.Results The COⅠgene sequences of 408 R. tanezumi specimens from the seven areas of Yunnan Province were successfully amplified. In the 639 bp COⅠgene sequence, the average percentages of T, C, A, and G bases were 29.67%, 25.67%, 27.67%, and 16.99%, respectively, and the proportion of A+T was higher than that of C+G. A total of 23 haplotypes were identified in the seven geographical populations. The haplotype diversity was 0.433-0.846, and the nucleotide diversity was 0.002 82-0.019 73. The overall haplotype diversity of 7 populations from high to low was: Dehong > Yuxi > Baoshan > Wenshan > Xishuangbanna > Lincang > Dali. The Wenshan, Dehong, and Yuxi populations were more diverse by nucleotide. The molecular phylogenetic analysis showed that the haplotypes of the seven populations were divided into three clades. The haplotype network showed that the haplotypes were distributed in a mixed pattern across different geographical populations. The Fst showed significant differences between different geographical populations (all P<0.05), except between Baoshan and Xishuangbanna, Lincang, and Wenshan, between Xishuangbanna and Lincang and Wenshan, and between Lincang and Wenshan. Gene flow data revealed a certain degree of genetic differentiation between Yushan populations and Dali, Baoshan, and Xishuangbanna populations, while there was a lack of gene exchange among other populations. The AMOVA analysis showed that the genetic variation among the seven R. tanezumi populations mainly was intra-population variation, with a low level of inter-population variation.Conclusions The R. tanezumi populations of the seven cities or prefectures have high genetic diversity, and genetic differentiation is present between some geographical populations. This study provides a reference for the study of molecular ecology of R. tanezumi.
  • Molecular characteristics of olfaction-related proteins in Haemaphysalis aponommoides
    LIU Zhi-tong, FENG Hao, WU Jia-hong, SUN Yi
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 274-280. https://doi.org/10.11853/j.issn.1003.8280.2024.03.003
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    Objective To investigate the molecular basis and mechanism of olfaction of ticks, and to identify the molecular structure of olfaction-related proteins of Haemaphysalis aponommoides and predict their function features.Methods The transcripts of olfaction-related proteins of Ha. aponommoides were acquired through transcriptome sequencing. The secondary and tertiary structures of these proteins were predicted with the use of ESPript 3.0 and Swiss-Model softwares. Based on molecular modeling, the structure features and protein-ligand interaction features of the olfaction-related proteins of Ha. aponommoides were explored.Results A total of 6 olfaction-related transcripts of Ha. aponommoides were acquired, and the corresponding protein sequences were highly homologous to Niemann-Pick C2 (NPC2), odorantbinding protein-like protein (OBPL), and microplusin-like protein in Ha. longicornis and Dermacentor silvarum. The OBPL domain consisted of 5 α-helices and 41.83% hydrophobic residues, forming a ligand-binding pocket, and in the NPC2 domain, 5 turns and 9 β-sheets comprised a ligand-binding pocket. The ligands of volatile odors were shown overlapped in the center of the pockets with their ligands.Conclusion The OBPL and NPC2 of Ha. longicornis possess a structure enabling odor sensation, suggesting their involvement in olfactory function in ticks.
  • Effects of ecdysone and juvenile hormone on arginine kinase genes CpAK1 and CpAK2 in Culex pipiens pallens
    QIAN Kun, GUAN Qing-qing, QIN Sheng-feng, WANG Yang
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 281-286. https://doi.org/10.11853/j.issn.1003.8280.2024.03.004
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    Objective To investigate whether the expression of arginine kinase genes (CpAK1 and CpAK2) in Culex pipiens pallens is affected by ecdysone and juvenile hormone and associated signaling pathways.Methods After being treated with 20-hydroxyecdysone (20E) and methoprene (a juvenile hormone analog) for different time durations, the mRNA and protein expression levels of CpAK1 and CpAK2 in Cx. pipiens pallens were measured by using reverse transcription real-time fluorescence quantitative PCR and western blot, respectively. After suppressing ecdysone signaling pathway-related genes (CpBR-C and CpECR) and ecdysone signaling pathway-related genes (CpMet and CpKr-h1) with RNA interference, the mRNA expression levels of CpAK1 and CpAK2 were measured.Results After 20E injection at the pupal stage, the mRNA expression level of CpAK1 was significantly reduced to 19.77% at 24 h, while the mRNA expression level of CpAK2 was up-regulated by 5.70 and 2.77 times at 6 h and 12 h, respectively; and 6 h after 20E treatment, the protein expression level of CpAK1 was significantly down-regulated, while the protein expression level of CpAK2 had no significant change. Methoprene treatment at the pupal stage significantly increased the CpAK1 mRNA level by 3.36 times at 24 h, and significantly decreased the CpAK2 mRNA level to 46.81% at 6 h and 39.34% at 12 h; and at 6 h and 12 h, the treatment significantly up-regulated the CpAK1 protein expression level, and significantly down-regulated the CpAK2 protein expression level. Suppressing CpBR-C caused a 2.35-fold increase in the mRNA expression level of CpAK1 and a decrease in the mRNA expression level of CpAK2 to only 2.80% of the control. After CpECR knockdown, the CpAK1 expression level was significantly increased by 8.13 times, while the CpAK2 expression level was significantly decreased by 42.79%. CpMet silencing led to a significantly down-regulated CpAK1 level to 43.87% and a significantly up-regulated CpAK2 level by 3.05 times. Suppressing CpKr-h1 resulted in a significantly down-regulated CpAK1 level to 13.59% and a significantly up-regulated CpAK2 level by 4.35 times.Conclusions 20E negatively regulates CpAK1 and positively regulates CpAK2, while methoprene positively regulates CpAK1 and negatively regulates CpAK2. Interfering with CpBR-C and CpECR significantly up-regulates CpAK1 and significantly down-regulates CpAK2. Interfering with CpMet and CpKr-h1 significantly down-regulates CpAK1 and significantly up-regulates CpAK2. During the pupation to eclosion of Cx. pipiens pallens, the expression of the two arginine kinases is regulated by ecdysone and juvenile hormone at relatively stable levels in general, and this regulatory mechanism is of great significance for maintaining ATP homeostasis.
  • Field application of Wolbachia-infected incompatible mosquitoes in communities at high risk for dengue fever
    GONG Jun-tao, LIANG Zi-mian, WEI Ying-yang, YOU Jian-wen, JIANG Wen-feng, XI Zhi-yong
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 287-292. https://doi.org/10.11853/j.issn.1003.8280.2024.03.005
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    Objective To test the mosquito control efficacy of releasing PAB males of Aedes albopictus artificially infected with wPip and naturally infected with wAlbA and wAlbB strains of Wolbachia into communities at high risk for dengue (high mosquito density, high human population density, and high vegetation coverage), so as to provide a scientific basis for field application of Wolbachia-infected incompatible mosquitoes in class-Ⅰ high risk areas for dengue fever in China.Methods A sufficient quantity of artificially reared male PAB Ae. albopictus were released twice a week into the Jinsha Xincheng community of Chancheng District, Foshan, Guangdong Province, China. At the same time, the density of Ae. albopictus at the release site was monitored using both BG-Traps and mosq-ovitraps, and was compared with the monitoring data of the control site during the same period to assess the population suppression efficacy of the release of PAB males. The two-sided Mann-Whitney U test was used to compare the density of trapped adults and average egg hatches between the release and control sites.Results Through 16 releases of male PAB mosquitoes spanning 17 weeks, the mosquito density at the release site was decreased substantially. The adult mosquito density was decreased by up to 93.67%, with an average reduction of 71.62%. The larva density was decreased by up to 89.45%, with an average reduction of 77.15%.Conclusion Wolbachia-based PAB male of Ae. albopictus population suppression can effectively and sustainably control the density of Ae. albopictus in communities at high risk for dengue, greatly reducing the risk of local spread of dengue fever.
  • Development and application of “rodent station” in the farmland of Sanya, Hainan Province, China
    GUO Tian-yu, ZHU Jian-qi, WANG Hui, ZENG Ying-chun, PAN Lei, GUO Tao
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 293-297. https://doi.org/10.11853/j.issn.1003.8280.2024.03.006
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    Objective To evaluate the effectiveness of a device called “rodent station” for rodent monitoring and control in farmland.Methods This device was placed on the field ridge of Nanfan Breeding Base in Yazhou District, Sanya, Hainan Province, China. The feasibility of the device for rodent surveillance was determined by using the built-in snap traps to monitor rodent density at night. Its efficacy for farmland rodent control was tested through bait feeding method. The palatability of base baits for rodent control was tested by selective feeding.Results From September to December in 2023, a total of 91 small mammals were captured in the four catches, including Rattus losea, R. tanezumi, R. norvegicus, and Mus musculus (in the order of the number of catches from large to low). The capture rate of four catches were 8.75%, 8.33%, 7.50%, and 4.58%, respectively, with 47.66% of efficacy against rodent. The selective feeding results showed that rodents preferred paddy, corn grits, corn flour, and rice from most to least.Conclusion The “rodent station” can be used as a tool to monitor and control rodent density in farmland and other outdoor environments, although the operation method needs to be improved.
    • Vector Surveillance
  • An analysis of plague surveillance results in Ordos, Inner Mongolia Autonomous Region, 2014-2022
    YAN Lu, WANG Sheng, GAO Dong, ZHENG Feng, WANG Na-na, YANG Chun-yan, JIN Shang-wu
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 298-302. https://doi.org/10.11853/j.issn.1003.8280.2024.03.007
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    Objective To investigate the number and distribution of main plague host populations for timely prediction of animal plague based on plague surveillance data, so as to provide a scientific basis for developing and implementing prevention and control measures against the occurrence of human plague.Methods The plague surveillance data of Ordos, Inner Mongolia Autonomous Region, China from 2014 to 2022 were collected, in which the data of Otog Front Banner (a national surveillance point) were systematically monitored in accordance with the National Plague Surveillance Program for Key Places, and the other surveillance points implemented the Inner Mongolia Plague Surveillance Program to monitor the main hosts, vector quantity, population density, etiology, and serology. The surveillance data were analyzed with the use of SPSS 25.0, and the rates were compared using the Chi-square test.Results A total of 7 721 rodents were captured, including 7 623 Meriones unguiculatus rodents (density ranging from 2.21 to 7.31 inds/hm2). The Meriones unguiculatus density of the key surveillance area and the general surveillance areas were 5.14 and 3.66 inds/hm2. The rodent body flea infestation rate was 33.49%, and the rate of flea infestation differed significantly between the key surveillance area (35.14%) and the general surveillance areas (32.73%) (χ2=8.512, P=0.004). The average booly flea index was 0.96. The dominant flea species were Xenopsylla conformis conformis and Nosopsyllus laevicepskuzenkovi. A total of 43 strains of Yersinia pestis were seperated, serology tested positive for 3 samples, and PCR tested positive for 4 nucleic acid samples.Conclusions Animal plague was active at the natural plague foci of Ordos, Inner Mongolia during 2014 to 2022, with a high risk of spread to humans. Efforts should be made to strengthen plague surveillance, enhance health education for the public, improve the capabilities of primary medical professionals, and ensure timely emergency capability, to avoid the occurrence of human plague and long-distance transmission of plague.
  • Population characteristics of Aedes larvae and dengue risk analysis based on vector surveillance data in Henan Province, China, 2019-2022
    ZHAO Qi, ZHANG Ye, FAN Jin-xing, YUE Si-ning, WANG An-qi, LIU Ji-qi
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 303-307. https://doi.org/10.11853/j.issn.1003.8280.2024.03.008
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    Objective To investigate the density and seasonality of the dengue vector Aedes populations in Henan Province, China, so as to provide a scientific basis for the risk assessment, monitoring, early-warning, and control of dengue fever.Methods From May to October of 2019 to 2022, Aedes vectors were monitored using the Breteau index (BI) method at 14 surveillance sites of Henan Province. Excel 2010 software was used to pool data, determine risk levels, and calculate the seasonal index. SPSS 25.0 software was used to perform the t-test and analysis of variance to compare the BI of different years and regions.Results The BI of Aedes mosquitoes from 2019 to 2022 were 15.31, 14.27, 11.34, and 12.32, respectively. The peaks occurred in July and August. Among 330 monitoring tasks over the four years, a regional spread risk was indicated in 85 (25.76%), an outbreak risk indicated in 70 (21.21%), a transmission risk indicated in 77 (23.33%), and no risk indicated in 98 (29.70%). The proportion of areas reaching a regional spread risk in southern Henan Province was higher than that in the northern part and along the Yellow River. The BI results of 2020, 2021, and 2022 were not significantly different from that of 2019 (all P>0.05). The BI showed no significant difference between regions (all P>0.05).Conclusions The density of Aedes mosquitoes is high in Henan Province, and there is a potential risk of dengue transmission in the peak season of Aedes for most surveillance sites. The number of imported dengue cases is expected to increase substantially in the future, highlighting the need for close attention to domestic and international dengue changes and emergency response and preparedness.
  • Changes in the population density, infestation rate, and insecticide resistance of Blattella germanica in Nanjing, China, 2012-2022
    ZHANG Yan, SONG Bing-dong, SUN Yan-qun, MIN Yue, CHEN Xue-min, LI Bi-han, SUN Nan, SUN Lu-yao, ZHANG Shou-gang
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 308-311. https://doi.org/10.11853/j.issn.1003.8280.2024.03.009
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    Objective To investigate changes in the density, infestation rate, and insecticide resistance of Blattella germanica in Nanjing, China, so as to provide a theoretical basis for scientific and rational use of insecticides.Methods From 2012 to 2022, the density and infestation rate of B. germanica were monitored in the 12 districts of Nanjing, and the resistance of the samples to propoxur, beta-cypermethrin, deltamethrin, acephate, and chlorpyrifos was tested by using the residual film method. The data were processed using the Probit module of SPSS 22.0 software. Spearman’s rank correlation analysis was conducted to correlate year with density, infestation rate, and resistance ratio.Results From 2012 to 2022, the densities of cockroaches were 1.01, 1.62, 2.17, 1.36, 1.21, 0.77, 0.58, 0.39, 0.39, 0.29, and 0.24 individuals/trap, respectively; and the infestation rates were 20.79%, 28.80%, 32.45%, 28.89%, 17.31%, 10.92%, 6.73%, 5.64%, 4.67%, 5.00%, and 3.36%, respectively. The density and infestation rate reached their peaks both in 2014, and decline since 2015, showing significant negative correlations between the year of investigation and the density and infestation rate (ρ=-0.897, P<0.001; ρ=-0.909, P<0.001). Propoxur resistance commenced at a low level in 2015, and the resistance ratio peaked at 4.73 in 2020, showing a significant positive correlation between the year and the resistance ratio (ρ=0.929, P=0.003). Beta-cypermethrin resistance increased to a medium to high level since 2015, and the resistance ratio reached the peak of 40.53 in 2020, showing a significant positive correlation between the year and the resistance ratio (ρ=0.821, P=0.023). Deltamethrin resistance increased to medium to high or even to extremely high levels since 2015, with no significant correlation between the year and the resistance ratio (ρ=0.714, P=0.111). The levels of resistance to chlorpyrifos and acephate were low in general, with no significant correlation between the year and the resistance ratio (ρ=-0.003, P=0.624; ρ=-0.771, P=0.072).Conclusions From 2012 to 2022, the density and infestation rate of B. germanica in Nanjing showed a downward trend, while the resistance to propoxur and beta-cypermethrin increased. The increasing resistance of B. germanica may lead to a rebound in its density and infestation rate, which should be paid more attention to.
  • Mosquito population density and seasonality based on surveillance analysis in Yancheng, Jiangsu Province, China, 2016-2023
    CUI Qian, YANG Shu-juan, ZHAO Yi-chao, JI Yu-qian, WANG Huan
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 312-315. https://doi.org/10.11853/j.issn.1003.8280.2024.03.010
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    Objective To investigate the species composition, density, and seasonal fluctuation of mosquitoes in Yancheng, Jiangsu Province, China, so as to provide a scientific basis for developing effective mosquito control measures and forecasting and early warning of mosquito-borne diseases.Methods Mosquito density was monitored by using the lamp trapping method in five types of habitats (urban residential areas, parks, hospitals, farmers’ houses, and livestock sheds) in Yancheng. The species composition, population density, and seasonal fluctuation of mosquitoes were analyzed. With SPSS 20.0 software, the Chi-square test was performed on the mosquito species composition ratios of different years and different habitats, analysis of variance was performed for different years, different species, and different habitats of mosquito densities, and trend analysis was performed for different years and different species of mosquito densities.Results From 2016 to 2023, a total of 132 432 female mosquitoes were caught in Yancheng, with an average density of 13.59 mosquitoes/light·night. Culex pipiens pallens/quinquefasciatus, Anopheles sinensis, and Cx. tritaeniorhynchus were the top three mosquito species, accounting for 68.62%, 13.95%, and 12.09% of the total catches, respectively. There was a significant difference in the composition of mosquito species between different years (χ2=9 026.399, P<0.001). Mosquito density and trend changes differed significantly in different mosquito species (both P<0.001). By habitat, the highest mosquito density was in livestock sheds (28.37 mosquitoes/light·night), while the lowest mosquito density was in hospitals (7.84 mosquitoes/light·night), with significant differences in the species composition ratio and density of mosquitoes between habitats (both P<0.001). Seasonal fluctuations in mosquito density showed unimodal distributions for all habitats and for all species, peaking during June and September.Conclusions Cx. pipiens pallens/quinquefasciatus, An. sinensis, and Cx. tritaeniorhynchus are the dominant species in Yancheng. Livestock sheds and farmers’ houses are the key places and June to September is the key time for mosquito control. Specific mosquito control measures should be taken based on the population distribution, density change, and seasonal fluctuation of mosquitoes.
    • Vector-borne Disease
  • Epidemiological characteristics and spatiotemporal clustering of scrub typhus in Shandong Province, China, 2006-2021
    SHI Yuan, LUN Xin-chang, CHEN Yi-jin, YU Sheng-nan, ZHENG Liang, WANG Zi-hao, LI Jin-yu, LI Xiu-jun, LU Liang
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 316-322. https://doi.org/10.11853/j.issn.1003.8280.2024.03.011
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    Objective To analyze the distribution characteristics, spatial and spatiotemporal clustering of scrub typhus in Shandong Province, China, and to identify high-risk areas, so as to provide scientific information for developing scrub typhus prevention and control strategies and measures.Methods Descriptive epidemiological methods, spatial autocorrelation analysis, and spatiotemporal clustering were used to analyze the spatiotemporal distribution characteristics of scrub typhus in Shandong Province from 2006 to 2021, and identified high-risk areas. ArcGIS 10.8 software was used to visualize the results.Results A total of 10 207 cases were reported in Shandong Province during 2006-2021, with a mean annual incidence rate of 0.64/100 000, and the incidence rate increased first and then decreased. Unimodal distributions were observed in the cases with respect to age (concentrated in 40-<80 years) and seasonality (peaking in October to November). By occupation, most of the patients were farmers. The global Moran’s I index of the annual incidence rate of scrub typhus was 0.203-0.676 (all P<0.05), indicating a positive spatial correlation at the district/county level. The local autocorrelation analysis results showed that high-high cluster areas mainly included Laiwu District and Gangcheng District of Jinan, Xintai City of Tai’an, Yishui County of Linyi, and Ju County and Wulian County of Rizhao. The spatial scan analysis results showed that the cases were spatially clustered, and the spatial clusters tended to expand from the central to the southern and eastern parts of Shandong Province from 2006 to 2021. The spatiotemporal scan analysis detected a spatiotemporal cluster area with a high incidence rate, which centered around Donggang District of Rizhao, with a radiation radius of 199.11 km, from October 2014 to November 2017 (risk ratio=8.24, log-likelihood ratio=4 107.176, P<0.01).Conclusions From 2006 to 2021, the incidence of scrub typhus in Shandong Province first increased and then decreased, with significant spatiotemporal clustering, and high-incidence cluster areas had been expanding continuously. Effective measures should be taken for key populations in high-incidence regions and seasons.
    • Early Warning and Forecast
  • Effects of precipitation on epizootic plague among Spermophilus undulatus at the northern Tianshan Mountains of Xinjiang Uygur Autonomous Region, China
    SUN Jing, WEI Wen-yu, ZHAN Shang, LI Fang, ZHAO Guo-yu, WANG Qi-guo, LUO Tao, WU Hai-yan, ZHANG Yu-jiang
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 323-328. https://doi.org/10.11853/j.issn.1003.8280.2024.03.012
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    Objective To investigate the effects of precipitation on the plague vectors and plague prevalence situation of Spermophilus undulatus at the northern Tianshan Mountains of Xinjiang Uygur Autonomous Region (Xinjiang).Methods The effects of precipitation on S. undulatus-associated plague vectors and plague prevalence, as well as the relationship between vectors and animal plague were analyzed through Spearman correlation analysis and generalized additive modeling.Results The current annual precipitation, the last spring-summer-autumn’ precipitation, and the last autumn-winter-spring’ precipitation were negatively correlated with the flea index and plague seroprevalence rate of S. undulatus. Among them, the correlations between the last annual precipitation and flea index, the last spring-summer-autumn’s precipitation and flea index were statistically significant (all P<0.05), and the correlations between the current and the last annual precipitation, the current spring-summer-autumn’, the current and the last autumn-winter-spring’ precipitation and the positive rate of F1 antibody to Yesinia pestis were all statistically significant (all P<0.05). The flea index and flea infestation rate were positively correlated with the plague seroprevalence rate (rs>0). The last spring-summer-autumn’ precipitation had a nonlinear relationship with the flea index. Nonlinear relationships were also observed between the autumn-winter-spring’ precipitation of the same year and the last year and plague seroprevalence rate. The flea index of the same year and that of the last year were linearly positively correlated with the plague seroprevalence rate.Conclusions The effects of precipitation on the flea index and plague prevalence of S. undulatus are complex. Increased precipitation can inhibit the growth of body flea populations, first promoting and then inhibiting plague epizootics, at a certain lag.
    • Technology and Method
  • Comparative study on three calculation methods for mosquito dominance
    LIU Quan-chao, ZOU Ya-ming, LAN Ce-jie
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 329-333. https://doi.org/10.11853/j.issn.1003.8280.2024.03.013
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    Objective To explore a dominance calculation method from biomass, temporal, and spatial dimensions that can provide more real reflection of species dominance.Methods The mosquito surveillance data of Wuxi, Jiangsu Province, China from 2012 to 2021 were analyzed using Excel 2019 software. The Kendall’s W coefficient was used to determine the consistency between the Time-Space index, Berger-Parker index, and McNaughton index. The results of the three calculation methods were compared using non-parametric Kruskal-Wallis H tests.Results The Kendall’s W coefficients for the three dominance calculation methods of all species were all >0.900, with a significant difference between them of Culex tritaeniorhynchus, Aedes albopictus, Anopheles sinensis (all P<0.05). There were no significant differences in the three dominance indices for Cx. pipiens pallens/quinquefasciatus and Ar. subalbatus (χ2=1.157, P=0.561; χ2=4.622, P=0.099). For Cx. tritaeniorhynchus, Ae. albopictus, and An. sinensis, the Time-Space index was all significantly lower than the Berger-Parker index (Z=-2.192, P=0.028; Z=-2.343, P=0.019; Z=-2.041, P=0.041), and for An. sinensis, the McNaughton index was significantly lower than the Berger-Parker index (Z=-2.192, P=0.028).Conclusion The Time-Space index can significantly improve the resolution of distribution heterogeneity of certain species, which can better reflect the true state of relative dominance of species.
  • Establishment of a multiplex real-time fluorescence quantitative PCR method for three tick-borne bacterial pathogens
    HU Wei-chao, LI Jin-yu, ZHAO Ning, LIU Qi-yong, WEN Hong-ling, WU Hai-xia
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 334-338. https://doi.org/10.11853/j.issn.1003.8280.2024.03.014
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    Objective To establish a multiplex real-time fluorescence quantitative PCR (qPCR) method for simultaneous detection of the common tick-borne pathogens Anaplasma phagocytophilum, Borrelia burgdorferi, and spotted fever group Rickettsia (SFGR).Methods Specific primers and TaqMan probes were designed against the conserved regions of pathogens,and a multiplex qPCR system was established and optimized. The specificity, sensitivity, repeatability,and accuracy for tick samples were evaluated.Results There were no cross reactivity with Escherichia coli,Leptospira interrogans, Brucella sp. in the detection of A. phagocytophilum, B. burgdorferi, and SFGR by the established multiplex qPCR method and showed high specificity. The sensitivity reached the order of 102 copies/μl, and the coefficient of variation for repeatability was less than 2.00%. In tick sample detection, the results of multiplex qPCR method were consistent with the singleplex qPCR method, with 100% consistency.Conclusion The established multiplex qPCR method for three tick-borne bacterial pathogens has high specificity and sensitivity, and can be used as a technical means for the detection of common tick-borne bacterial pathogens.
  • A new species of the genus Heizmannia from Yingjiang County, Yunnan Province, China （Diptera： Culicidae）
    WU Lin-bo, XU Xiang, ZENG Xu-can, GUO Xiao-lian, DONG Xue-shu
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 339-342. https://doi.org/10.11853/j.issn.1003.8280.2024.03.015
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    This paper describes a new species of Heizmannia (Mattinglyia) yingjiangensis sp. nov collected from Tongbiguan Nature Reserve, Yingjiang County, Dehong Dai and Jingpo Autonomous Prefecture, Yunnan Province, China in August 2020. The main features of the new species include a uniformly dark proboscis; the mesoscutum densely covered with light yellow narrow scales, the paratergite with dark black manes and without scales, and the posterotergite with fine scales; the urotergite uniformly and densely covered with dark blue broad scales with a metallic luster. Males have antennae of about the same length as the proboscis, with whorls of plumose hairs on them; and the distimere of the male genitalia is not enlarged, with a well-developed dorsal basal inner lobe, which has 2 coarse spiny bristles and 5 spiny bristles with slightly curved ends and a number of fine manes. The type specimens are preserved in the mosquito collection room of Yunnan Institute of Parasitic Diseases.
  • Study on the relationship between the community structure of ectoparasitic flea of plague host and the epidemic intensity of epizootic plague in the mountain plague foci in Xinjiang Uygur Autonomous Region
    WEI Wen-yu, SUN Jing, LI Fang, ZHAN Shang, ZHAO Guo-yu, LUO Tao, WU Hai-yan, ZHANG Yu-jiang
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 343-348. https://doi.org/10.11853/j.issn.1003.8280.2024.03.016
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    Objective To understand and analyze the relationship between the community structure of the main host animal ectoparasitic flea and the epidemic of epizootic plague and its influence on the epidemic of animal plague in four types of mountain plague natural foci in Xinjiang Uygur Autonomous Region (Xinjiang).Methods The community ecology method was used to calculate the diversity, evenness, dominance and richness of the flea community. Wilcoxon rank sum test was used to analyze the community structure difference of flea, and Spearman rank correlation test was used to analyze the correlation between the ecological structure of flea and the positive rate of serum antibody of host animal. Principal component analysis was used to extract the principal components of ecological indicators, and the principal components were incorporated into generalized addition model (GAM) and random forest model to analyze the relationship between the principal components and the epidemic intensity of animal plague.Results There were statistically significant differences in the ecological structure of the host active flea community in the four types of mountain plague focus (all P<0.001), and there were positive correlations between the flea infection rate, flea index, flea richness and diversity and the positive rate of host active serum antibodies (rs=0.682, P<0.001; rs=0.686, P<0.001; rs=0.529, P<0.001;rs=0.339, P=0.023). GAM analysis showed that the positive rate of host antibody was linearly positively correlated with principal component 1 (PC1), which consisted of flea index and flea infection rate, and nonlinearly correlated with principal component 2 (PC2), which consisted of flea diversity and abundance. The random forest model fitting results showed that the importance scores of PC1 and PC2 factors were 24.84 and 4.52, respectively.Conclusions The flea population in the mountainous plague foci of Xinjiang is rich in diversity. The increase of flea index and flea infection rate may enhance the epidemic intensity of animal plague, and the diversity and species richness of flea may regulate the epidemic of animal plague.
    • Investigation
  • Catalogue of chigger mites on small mammals in Dehong Dai and Jingpo Autonomous Prefecture of Yunnan Province along the China-Myanmar border
    LIU Ru-jin, GUO Xian-guo, ZHAO Cheng-fu, ZHANG Zhi-wei, ZHAO Ya-fei, FAN Rong, SONG Wen-yu
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 349-357. https://doi.org/10.11853/j.issn.1003.8280.2024.03.017
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    Objective To investigate the species composition and distribution of chigger mites on the body surface of small mammals in the Dehong Dai and Jingpo Autonomous Prefecture (Dehong Prefecture) of Yunnan Province along the China-Myanmar border.Methods A field investigation was carried out in four cities and counties of Dehong Prefecture from 2008 to 2022. Chigger mites were collected from the body surface of small mammals such as rodents. Chigger mite slide specimens were prepared for identification and classification under a microscope. The constituent ratio of dominant chigger mite species was calculated using Excel 2021 software. According to the taxonomic system of chigger mites, a taxonomic catalogue of the mites was systematically sorted out based on the identification results.Results A total of 1 760 rodents and other small mammals were captured, belong to 27 species, 16 genera, 9 families, and 3 orders. Rattus tanezumi (917/1 760, 52.10%), Eothenomys miletus (296/1 760, 16.82%), Suncus murinus (126/1 760, 7.16%), and R. andamanensis (122/1 760, 6.93%) were the dominant host animals for chigger mites. From the body surface of those small mammals, a total of 9 309 larval chigger mites were identified, involving 117 species, 16 genera, 2 subfamilies, and 1 family, with highly abundant and diverse species. Leptotrombidium deliense (1 597/9 309, 17.16%), Walchia ewingi (1 510/9 309, 16.22%), and Gahrliepia longipedalis (1 329/9 309,14.28%) were the dominant mite species, with a total constituent ratio of 47.65% (4 436/9 309).Conclusion In the epidemic foci of scrub typhus in Dehong Prefecture, there are abundant species of chigger mites, and L. deliense, W. ewingi, and G. longipedalis are dominant mite species.
  • Detection of Songling virus from ticks in Huanan County, Heilongjiang Province, China
    HOU Ze-ying, LIU Feng-ming, ZHAO Ji-min, LI Chun-yu, LI De, WANG Rui-chen, ZHANG Wei-jia, YAO Xiao-hui, LI Fan, NIE Kai, FU Shi-hong, YIN Qi-kai, CUI Qian-qian, XU Song-tao, LI Xing-zhou, BAO Ming-jia, WANG Huan-yu
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 358-362. https://doi.org/10.11853/j.issn.1003.8280.2024.03.018
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    Objective To detect Songling virus and distribution in ticks collected from Huanan County, Jiamusi, Heilongjiang Province China in 2023.Methods Tick species was identified using morphological methods. The collected tick specimens were examined for Songling virus (SGLV) by using reverse transcription real-time fluorescence quantitative polymerase chain reaction (RT-qPCR). Positive products were sequenced by Sanger sequencing.Results A total of 421 tick specimens were collected, included Dermacentor silvarum (184, 43.71%), Ixodes persulcatus (115, 27.32%), Haemaphysalis japonica (32, 7.60%), H. concinna (43, 10.21%), H. longicornis (7, 1.66%), and 40 unrecognized nymphs (9.50%). Among them, one female H. concinna (ID: 2023JMS365) was tested positive for SGLV nucleic acids by RT-qPCR. The phylogenetic analysis revealed that the nucleotide identencies of the L, M, and S segments of the 2023JMS365 genome were 96.78%, 92.11%, and 97.59% respectively with the SGLV reference strain HLJ1202, and the amino acid identencies were 99.22%, 97.50%, and 93.28%, respectively.Conclusion SGLV was first detected in H. concinna ticks in Huanan County, Jiamusi City.
  • A serological survey of infection with Severe fever with thrombocytopenia syndrome virus in rural residents and host animals in Dongyang, Zhejiang Province
    WU Ai-lan, JIA Xu-qiang, GUO Bin, CHEN Kang, WU Zhen-hua, ZHU Xiang, LI Yue-hua, JIN Xu-jing, XU Yue-chen, ZHANG Jing
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 363-368. https://doi.org/10.11853/j.issn.1003.8280.2024.03.019
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    Objective To investigate the prevalence of infection with Dabie bandavirus, also know as Severe fever with thrombocytopenia syndrome virus (SFTSV), in rural residents and host animals in Dongyang, Zhejiang Province, China, and analyze its influencing factors, so as to provide a theoretical basis for the control of the epidemic of severe fever with thrombocytopenia syndrome (SFTS).Methods Three townships with reported SFTS cases were selected, and another three townships with similar topographic features but without case reports were selected by 1:1 matching. Two villages were selected from each township as the study area to collect serum samples from residents and host animals. Human serum samples were tested for SFTSV antibodies by enzyme-linked immunosorbent assay, while animal serum samples were tested by double antigen sandwich assay. SPSS 18.0 software was used to analyze the data. The Chi-square test was used for rate comparison. A logistic regression analysis was performed to determine risk factors.Results A total of 1 117 rural residents were examined, of whom 22 were positive for SFTSV antibodies, with a positive rate of 1.97%. There were no significant differences in the positive rate of SFTSV antibodies between sexes, ages, and occupations (all P>0.05). According to the logistic regression analysis, the potential risk factors for SFTSV infection included previous reports of SFTS cases in villages of residence (odds ratio [OR]=2.994, 95% confidence interval [CI]: 1.277-7.021, P<0.05) and a history of tick bites in the last five years (OR=3.563, 95%CI: 1.227-10.342, P<0.05). The positive rates of SFTSV antibodies of sheep, dogs, cattle, and pigs were 45.83% (11/24), 7.69% (3/39), 0 (0/7), and 0 (0/20), respectively, showing a significant difference between them (χ2=23.559, P<0.001). Among 183 rodents tested, 1 was positive for SFTSV antibodies.Conclusions In some rural areas of Dongyang, SFTSV antibodies were detected in both residents and animal hosts, and the antibody detection rate was higher in areas with reported cases than in those without case reports, suggesting that the prevalence of SFTSV infection in Dongyang exceeds expectations. In addition to tick control, future SFTS prevention and control efforts should also focus on strengthening animal management, health promotion and education, and rodent control.
  • An investigation of tick-borne pathogens in parts of northeast China
    HUANG Guan-peng, WU Qiong, MA You-xin, MAO En-rong, HUANG Xiao-yang, WANG Zhuo, ZHAO Hong-ming, LENG Guo-shuang, LI Bing, WANG You-jin, WU Yi-min
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 369-373. https://doi.org/10.11853/j.issn.1003.8280.2024.03.020
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    Objective To investigate the pathogens carried by ticks in three northeastern provinces of China and provide reference basis for the prevention and control of tick borne diseases.Methods From 2012 to 2013 and in 2016, tick specimens were collected from 11 counties and cities of northeastern China. Spotted fever group rickettsiae (SFGR) and Bartonella by PCR were tested, Candidatus Neoehrlichia mikurensis, Ehrlichia chaffeensis, and Francisella tularensis by nested PCR, and Borrelia burgdorferi and Babesia microti by quantitative real-time PCR.Results The detection rate was 9.10% for SFGR, 4.10% for E. chaffeensis, 0.70% for F. tularensis, 14.95% for Bor. burgdorferi, and 1.87% for Bab. microti, with a significant difference (χ2=42.808, P<0.001). Bor. burgdorferi and SFGR were most frequently detected, while Candidatus Neoehrlichia mikurensis and Bartonella were not found. There were significant differences between tick species in the positive rates of SFGR (χ2=12.291, P=0.016), Bor. burgdorferi (χ2=23.409, P<0.001), and Bab. microti (χ2=11.592, P=0.028).Conclusions Ticks carry a variety of pathogens in northeast China, in which Bor. burgdorferi and SFGR are more common, and pathogen species differ between tick species, suggesting that these areas should strengthen tick-borne pathogen surveillance to inform the prevention and control of tick-borne diseases.
  • Distribution of major pathogens carried by Spermophilus dauricus in the eastern grassland of Inner Mongolia Autonomous Region, China
    LI Jin-yu, BAI Xue-feng, YAN Wen-zhe, LI Ke, WANG Zi-hao, SHI Yuan, LU Liang, LI Gui-chang, WEN Hong-ling, ZHAO Ning, LIU Qi-yong
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 374-380. https://doi.org/10.11853/j.issn.1003.8280.2024.03.021
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    Objective To investigate the species and distribution of pathogens carried by Spermophilus dauricus in the eastern grassland of Inner Mongolia Autonomous Region, China, so as to provide a scientific reference for local control of rodent-borne diseases and pathogen surveillance.Methods S. dauricus rodents were captured from eight sites of Inner Mongolia Autonomous Region in May, July, and September 2021. The liver specimens of the captured rodents were examined using quantitative PCR (qPCR)/reverse transcription qPCR (RT-qPCR) for eight important pathogens, including Rickettsia mooseri, Anaplasma phagocytophilum, Orientia tsutsugamushi, Francisella tularensis, Bartonella, Leptospira interrogans, Dabie bandavirus, and Hantavirus. The Chi-square test was used to analyze the differences in the positive rate of pathogens S. dauricus among sampling sites, seasons, sexes and different ectoparasite (ticks, mites, fleas) infection status.Results A total of 181 S. dauricus were captured, with a capture rate of 1.44% and a ectoparasite infection rate of 77.35%. The detection rate of Bartonella was 39.23% (71/181), while the detection rates of the other seven pathogens ranged from 0 to 8.84%. The Bartonella detection rate differed significantly between seasons (χ2=26.795, P<0.001), with the highest positive rate of 66.67% occurring in September, followed by 52.75% in July. There was a significant difference in the Bartonella detection rates of different sampling sites (χ2=18.697, P=0.005), which were 50.00%, 42.86%, and 24.62% for N1, N3, and N5 sites, respectively and 40.00%, 42.86%, and 72.73% for W2, W3, and W5 sites, respectively. There were no significant differences in the positive rate of Bartonella between sexes and between ectoparasite infection status (all P>0.05). There were no significant differences in the infection rate of pathogens other than Bartonella in different months (seasons), sampling sites, sexes, and parasite infection status (all P>0.05). The positive rate of co-infection with two or more pathogens was 8.84%.Conclusions S. dauricus carries a variety of pathogens, of which Bartonella is most noteworthy, and there is co-infection with multiple pathogens in S. dauricus. The detection rate of Bartonella decreases with increasing temperature from northern to southern sampling sites, and increases with increasing humidity from western to eastern sampling sites. Early autumn is the key season for S. dauricus control.
  • Detection and genotyping of pathogenic bacteria carried by Rhipicephalus microplus in Ji’an,Jiangxi Province,China
    ZENG Yu, LIU Zhi-yun, DUAN Li-ke, HOU Xue-xia, ZHANG Lin, HE Li-juan, HAO Qin
    Chinese Journal of Vector Biology and Control. 2024, 35(3): 381-388. https://doi.org/10.11853/j.issn.1003.8280.2024.03.022
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    Objective To investigate parasitic ticks and their pathogenic bacteria in Ji’an City, Jiangxi Province,China.Methods A total of 417 parasitic ticks were collected from the body surface of cattle in Yongxin County, Ji’an County, and Yongfeng County of Ji’an City from June 2022 to June 2023. Tick species was identified by morphological examination and 16S rDNA gene analysis. The collected ticks were examined with traditional PCR and nested PCR for six species of tick-borne pathogens,including Borrelia burgdorferi (B.b), B. miyamotoi (B.m), spotted fever group Rickettsia (SFGR), Ehrlichia chaffeensis (EC), Coxiella burnetii (C.b), and Anaplasma phagocytophilum (AP). Positive samples were sequenced.Results All the 417 ticks were identified as Rhipicephalus microplus, and 58 of them tested positive for the pathogens described, with a positive rate of 13.91%. In Yongxin County, B.b, SFGR, and C.b were detected, and the positive rate of B.b was highest (8.99%). In Ji’an County, B.b, EC, and C.b were detected, and the positive rate of C.b was highest (9.21%). In Yongfeng County, B.b, SFGR, C.b, and AP were detected, and the positive rate of SFGR was highest (10.32%). Additionally, co-infections with B. b and other tick-borne pathogens were present in all the three counties. The phylogenetic analysis showed that the parasitic ticks of Ji’an carried three genotypes of B.b (B. yangzensis, B. garinii, and B. barvariensis) and two types of SFGR (R. slovaca and Candidatus R. jingxinensis).Conclusions The species and predominant genotypes of pathogenic bacteria carried by parasitic ticks vary in different counties of Ji’an, and there is a phenomenon of co-infections with multiple bacteria, indicating that pathogenic bacteria carriage in local ticks is complex. Further study and surveillance should be conducted to prevent and control tick-borne diseases in Jiangxi Province.
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