Marmota himalayana is an endemic species of the Qinghai-Tibet Plateau and an important part of its ecosystem, which plays a significant role in maintaining the ecological balance of the natural foci of plague. The distribution of marmots is influenced by environmental factors such as climate, soil, and vegetation, thereby determining the distribution and changes of natural plague foci and the risk of associated plague epizootics. In other words, the distribution of geographical landscape elements and the main host animals of plague play a decisive role in the distribution area of natural plague foci. Ecological research on M. himalayana has been widely reported. This paper reviews the research status in China and globally from the aspects of ecological, burrow, and habitat characteristics of M. himalayana, with the aim to improve the understanding of M. himalayana ecology and promote the application of ecology in plague prevention and control.

Objective To investigate the distribution of Oncomelania hupensis snails in Yingde, Guangdong province, China in 2019, and to provide a basis for the formulation of scientific O. hupensis snail control measures. Methods By consulting and sorting out relevant historical data, and conducting on-site environment-based sampling or system sampling combined with environment-based sampling surveys, the breeding of O. hupensis snails was investigated. Excel 2007 software was used to enter the results of investigation. SPSS 20.0 software was used to perform the statistical analysis. The Chi-square test was used to compare the rate. Results Five villages where snails had bred in Yingde were investigated, including 808 suspected breeding habitats, among which 23 habitats were found with snails, with an area of 105 648.94 m ². The mean density of living snails was 2.09 snails/0.1 m ², and the mean occurrence rate of living snails was 18.50%. A total of 5 413 O. hupensis snails were dissected, and no schistosome-infected snails were found. Conclusion There are many suitable habitats for the breeding of O. hupensis snails in Yingde. It is necessary to strengthen snail investigation, filing, and environmental improvement for the suspected breeding habitats.

Objective To investigate the flea control effect in some rural residential areas of Xinjiang Uygur autonomous region, China. Methods Some rural residential areas in Xinjiang were selected as the experimental areas, and 8% beta-cypermethrin wettable powder diluted 100 times was used to control the fleas via residual spraying. The flea infestation rate, flea index, and biting rate were compared before and after the flea control to evaluate the control effect. The independent samples t-test or one-way analysis of variance and chi-square test were used to compare the flea index, flea infestation rate, and biting rate. Results Before the flea control, the flea infestation rate was 86.25% (69/80) and the total flea index was 0.23 (213/914), with no significant differences between different villages ( P=0.599, Fisher's exact test; F=0.103, P=0.924). The biting rate was 62.71% (148/236), 89.47% (34/38), and 83.82% (57/68), respectively, in adults, young children (6 months to 4 years of age), and elder children (6-8 years of age). The biting rate was significantly higher in young and elder children than in adults ( χ ²=10.510, P=0.001; χ ²=10.714, P=0.001). The biting rate of cadres stationed in the villages was 76.29% (74/97). On days 2-3 after the flea control, the flea infestation rate and total flea index were significantly reduced to 6.25% (5/80) and 0.02 (19/914), respectively ( χ ²=102.979, P<0.001; t=38.476, P<0.001); the biting rate was significantly reduced to 4.41% (10/227), 8.11% (3/37), and 6.06% (4/66), respectively, in adults, young children, and elder children ( χ ²=174.983, 49.653, and 85.613, all P<0.001); the biting rate of cadres stationed in the villages was significantly reduced to 2.94% (3/102) ( χ ²=112.757, P<0.001). Conclusion Residual spraying with 8% beta-cypermethrin wettable powder diluted 100 times had a good effect of flea control in the rural residential areas in Xinjiang, which holds promise for application.

Objective To investigate the prevalence of animal plague by analyzing the epidemic situation of animal plague in southern Tianshan mountains in Xinjiang Uygur Autonomous Region (Xinjiang), China and eastern Pamir plateau of Central Asia's border areas (areas bordering Kyrgyz Republic and the Republic of Tajikistan in the northern and western parts of Kizilsu Kirghiz autonomous prefecture[KKAP]) from 2014 to 2018, to provide strong data support for human plague prevention and control, and to boost the Belt and Road Initiative. Methods Based on the network reporting data from China Information System for Disease Control and Prevention and the geographic features of KKAP and characteristics of plague hosts in KKAP, the sample study areas were divided into two parts:the natural plague foci of Marmota baibacina in southern Tianshan mountains (Artux city, Wuqia county, and Akqi county) and the natural plague foci of Marmota caudata in Pamir plateau-Alai mountains (Wuqia county and Akto county). Spatial epidemiological and statistical methods combined with the geographic features were used to analyze the epidemic characteristics of animal plague in southern Tianshan mountains in Xinjiang and eastern Pamir plateau in recent five years. Results The host density investigation showed that the densities of marmots in the two study areas in July were higher than or equal to those in May during all the study years except for individual years during which the densities in May were higher than those in July. The vector flea investigation showed a significant difference between the two areas in dominant flea species, and the flea infection rate and flea index were relatively stable. In the past five years, 4 692 pieces of marmot serum anti-plague F1 antibody testing data and 762 pieces of canine serum testing data were obtained, among which 33 pieces of canine serum testing data yielded positive results (positive rate:4.33%). Thirty-six marmots that died of diseases were identified and three Yersinia pestis strains were isolated (positive rate:8.33%). Conclusion The numbers of hosts,vector populations and population structure remain at relatively stable levels in the natural plague foci in the southwestern segment of southern Tianshan mountains and the eastern segment of Pamir plateau-Alai mountains. The epidemic situation of animal plague tends to be relatively stable in these areas, but they still remain as epidemic foci of plague and local animal plague epidemics can be observed.

Co-constructing Silk Road Economic Belt and 21st Century Maritime Silk Road are major initiatives for China to deepen reform and opening-up, especially opening up to the west. As a core area of Silk Road Economic Belt, Xinjiang Uygur Autonomous Region (Xinjiang), once the "pocket bottom" of the inland, has become an important logistics distribution center and transportation hub of the Belt and Road. Such important strategic positioning signifies a major historical opportunity for the substantial development of Xinjiang Uygur Autonomous Region (Xinjiang). However, opportunities and challenges coexist. Many countries along the Silk Road are natural foci of plague; in addition, Xinjiang has a natural plague foci of 330 000 square kilometers. With the increasingly frequent exchanges between countries along the Road such as international transportation and tourism, the probability of long-distance transportation of plague-infected animals and their products from plague foci to non-plague foci as well as densely populated areas also increases, which raises the risk of sudden plague outbreaks outside plague foci. In the new era, how to do well in the prevention and control of plague in Xinjiang, how to promote cooperation in plague surveillance, plague prevention and control, and health emergency after plague outbreaks among countries along the Road, and how to boost the development of Healthy Silk Road are particularly important. To this end, this article reviews the risk of plague and its prevention and control strategies in Xinjiang during the development of the Silk Road Economic Belt, with a view to providing a reference for future plague prevention and control.

Objective To investigate the efficiency and practicability of bow-shaped clamps in field control of Spermophilus undulatus, and to provide a reference basis for deratization in future. Methods With the large-size clips as a control, bow-shaped clamps and the trap-day method were used to capture S. undulatus in Guertu plague surveillance sites in Wusu county of Xinjiang Uygur Autonomous Region from May to July, 2018. The χ ² test and t test were used to compare the capture rate and installation efficiency of different methods. Results The azimuth angle of bow-shaped clamps was one time larger than that of the large-size clips. The mean capture rate of bow-shaped clamps was higher than that of the large-size clips ( P=0.000), and the installation efficiency of bow-shaped clamps was two times than that of the large-size clips. Conclusion Bow-shaped clamps have the features of large azimuth angle, strong anti-escape function, simple installation, and no need for baits. Therefore, they can be used to control S. undulatus.

Objective To investigate the prevalence of animal plague in Marmota baibacina-Spermophilus undulatus natural focus and provide basis for prevention and control of plague. Methods Surveillance was carried out on the density of S. undulatus and M. baibacina in Guertu between 2006 and 2010 according to the rule of plague prevention and surveillance in Xinjiang. The four-step test was performed for inspect visceral organs and body fleas of S. undulatus. Indirect hemagglutination assay was used to detect F1 antibody in the serum of S. undulatus and shepherd dogs. Statistical analysis was performed using Excel 2007 software according to animal plague epidemiology. Results The mean density of S. undulatus and M. baibacina in Guertu plague focus between 2006 and 2010 were 14.64/hm ² and 0.61/hm ², respectively. The rate of carrying flea was 90.72% and the mean flea index was 7.09. The serological test showed that 130 were positive for F1 antibody among 2 532 serum samples of S. undulatus, and 8 were positive for F1 antibody among 132 serum samples of shepherd dogs. A total of 67 strains of Yersinia pestis were isolated from S. undulatus and its body fleas. Conclusion The plague among S. undulatus in Xinjiang has been prevalent for many years, and human beings might be infected. Thus, surveillance should be performed actively and publicity should be also carried out at the same time.

Immunological detection technology for Yersinia pestis is an important tool to master the epidemic dynamics of plague, discover new plague foci, and confirm suspected plague cases. Now, the commonly used immunological detection methods for Y. pestis include indirect hemagglutination assay (IHA), enzyme-linked immunosorbent assay (ELISA), radioimmunoprecipitation assay (RIPA), colloidal gold immunochromatography assay (GICA), and enzyme immunostaining technique (EIT). Each detection technology has its advantages and disadvantages. IHA and ELISA are mainly used for plague detection. GICA and EIT are used for human plague epidemics. RIPA is no longer used due to its radioactive harm to humans. In the actual plague prevention and control, a combination of multiple detection technologies, which could avoid false-positives and achieve better results, would be a better choice.

Objective To determine the density and life stages of Aedes, the important dengue vectors, during winter in Jinghong, and to provide a scientific basis for the prevention and control of winter-spring dengue fever in Jinghong. Methods From November 2017 to April 2018, five investigation regions were selected in the eastern, southern, western, northern, and central parts of the downtown of Jinghong, respectively. Using backpack aspirators, the density of adult Aedes mosquitoes was investigated in underground garages, park lawn, hotels, greenhouses, and residential houses in each region. The Breteau index (BI) was used to investigate the breeding and composition of Aedes larvae in water containers in each region. Sediment samples, maybe included eggs of Aedes mosquito, were collected from various Aedes breeding containers in each region. Eggs of Aedes mosquito in the samples were fed in laboratory to adult mosquitoes for identification and counting. The SPSS 19.0 software was used to process the data. The BI value and positive rate of containers for mosquito breeding were compared between different months by χ ² test, partition of χ ² analysis, and Kruskal-Wallis test. Results A total of 57 adult Aedes mosquitoes were captured, consisting of 11 Ae. aegypti mosquitoes and 46 Ae. albopictus mosquitoes. In those mosquitoes, 46 were captured in residential houses, 9 in park lawn, and 2 in greenhouses. The density of adult Aedes in each month was 9.17, 4.00, 0.00, 0.22, 0.67, and 2.67 mosquitoes/person·hour, respectively, from November to April of the next year, suggesting that the density of adult mosquitoes gradually decreased from November to January of the next year and gradually went up from February to April. In this study, 34 out of 1 500 households and 38 out of 849 water containers were positive for Aedes. The overall BI, container index, and house index were 2.53, 4.48%, and 2.27, respectively. From November to April of the next year, the density of Aedes larvae in each month was 2.80, 0.80, 2.80, 2.40, 2.00, and 4.40 mosquitoes/person·hour, respectively. The main breeding container was bucket, followed by vase. The positive rates of permanent containers, vases, used tires, buckets, waste bottles, and other water containers for Ae. aegypti breeding were 2.42%, 3.56%, 36.36%, 5.63%, 1.82%, and 4.85%, respectively. According to χ ² test and partition of χ ² analysis, there was a significant difference in the positive rate for Aedes breeding between different types of containers ( χ ²=29.570, P=0.000). Among those containers, used tires had the highest positive rate. A total of 671 dry sediment samples were collected from various types of water containers. In those samples, 8 were positive for Aedes eggs, yielding a positive rate of 1.19%. A total of 126 Aedes mosquitoes were born from the 8 samples, consisting of 107 (84.92%) Ae. aegypti mosquitoes and 19 (15.08%) Ae. albopictus mosquitoes. The positive rates of vases, used tires, buckets, wastes, and other containers for Aedes eggs were 0.80%, 3.03%, 2.70%, 2.44%, and 1.67%, respectively. There was no significant difference in the positive rate for eggs between various types of containers ( H=8.646, P=0.076). Conclusion The two important dengue vectors, Ae. aegypti and Ae. albopictus, were active during winter in Jinghong. Both of them existed in forms of adult, larvae, and egg. The density of adult mosquitoes and larvae started to go up in early April. In order to reduce the density of Aedes mosquitoes in Jinghong, multiple departments and all the residents are recommended to attend the government-led sanitation activities every April that focus on removing larval breeding sites and are accompanied by anti-mosquito spray. In the meanwhile, methods and tools need to be developed to remove and kill Aedes eggs in container sediments.

Objective To understand the infection status of Bartonella in Citellus undulatus from Guertu, and to provide the basis for risk early warning and control measures of rodent-borne diseases. Methods In total, 86 C. undulatus were collected from Chagangguole, Bulanbulake and Baishitou by bow-shaped clip method during 24 hours, the kidneys of the captured rodents were sampled under aseptic condition, genome DNA was extracted and detected by real-time fluorescence quantitative PCR targeting ssrA of Bartonella. The rate of infection were calculated and analyzed by cp test (cp value). Results A total of 86 C. undulatus were tested, the infection rate of Bartonella in those rodents was 48.84% (42/86). The cp of positive samples had the highest value of 37.83 and the lowest value of 27.49, 88.10% of positive samples was in the "35.00-37.83" range. The infection rate of Chagangguole, Bulanlulake and Baishitou were 48.48%, 60.87%, 40.00%, respectively. The flea infection rate and flea index in Bulanlulake were higher than those of other places, the infection rate had no correlation with the flea infection in Guertu ( P>0.05). Conclusion There were natural infection of Bartonella among C. undulatus in Guertu, with tendency of wide spread, but pathogen loads were relatively low in wild rodents.

Objective Through the investigation of the plague natural infectious at Qinghe county in Altay district, to master the situation of plague natural foci in this district. Methods The investigation of rodents on fauna, species, density, and ectoparasites were conducted by the sandwich methods, route methods, site observation and others in Daqinghe, Xiaoqinghe, Bianhaizi, Zhonghaizi, Huahaizi, Halabaliqike, Qiaolakesaiyi and other mountains at Qinghe in Xinjiang during 2015-2017. IHA was used to test F1 antibody/antigen against plague; "Four-step test" was used to test Yersinia pestis. Results The preliminary investigation of mountains in Qinghe indicated that there were 5 species of rodents belonging to 5 genera and 3 families, including Marmota baibacina, Citellus undulatus, Clethrionomys rufocanus, Microtus gregalis, and Ochotona alpina. Among these, M. baibacina were distributed in forest steppe zones and mountain grassland at the altitude of 1 750-2 700 m, average density was 0.31 catches per hectare; C. undulatus were distributed in Huahaizi, Zhonghaizi, Bianhaizi, Halabaliqike, and Qiaolakesaiyi districts, average density was 4.60 catches C. undulatus per hectare; Four M. baibacinas and 552 C. undulatus were captured, infestation rate of fleas was 25% and 45%, respectively. The study used "Four-steptest" to detect Y. pestis, and used plague RIHA to test F1 antigen in 4 viscus samples from M. baibacina, 552 viscus samples from C. undulatus, 13 viscus samples and skeletons of self-dead M. baibacina and C. undulatus, as well as 583 fleas. The results of "Four-step test" and F1 antigen were negative. The IHA was used to test 552 serums of C. undulatus,the results indicated 1 serum sample was positive, positive rate was 0.18%, antibody titers was 1:2 ⁹. The IHA was also used to test 129 sera of herding dogs, the results indicated 6 sera were positive, positive rate was 4.65%, the mean antibody titers was 1:2 ^3.83. Conclusion The study indicated the mountain areas have potential plague natural infections at Qinghe county in Xinjiang. It is suggested to conduct further investigation on plague foci of natural infections at Qinghe county in Xinjiang.

Objective We studied the DFR (different region)-type data of Yersinia pestis in Xinlong county and provided a scientific basis for prevention and treatment of plague. Methods One strain of Y. pestis isolated from plague foci in Xinlong county compared with 16 strains of Y. pestis isolated from other plague foci in Ganzi Tibeian Autonomous Prefecture, and genotyped by primers of 23 DFRs and PMT1. To confirm the genotype of strains from Xinlong county, we analyzed the data by BioNumerics 6.6 software. Results The DFR-type of Y. pestis in Xinlong county was same as DFR-type of other counties, all belonging to Genomovar05 type, but different from DFR-type of Shiqu county strains. Conclusion Genotype of Y. pestis isolated from Xinlong county is Genomovar05 type, and Xinlong plague natural foci is the part of Marmota himalayana plague natural foci of Tibetan Plateau.

Objective To investigate the natural infection with Dengue virus(DENV) and Japanese encephalitis virus (JEV) in mosquitoes in Jinghong city, Xishuangbanna prefecture, Yunnan province, China, and provide the scientific basis for its prevention and control. Methods Mosquito samples were collected from urban area of Jinghong in August and September 2015. Mosquito samples were tested for the nucleic acid of DENV and JEV by RT-PCR assay, and positive specimens were sequenced for C/PrM gene for homology and phylogenetic analyses. Results A total of 2 009 mosquitoes were collected in urban area of Jinghong. Aedes albopictus, Ae. aegypti, Culex(species not identified) and Ae. vexans were 896, 477, 634, and 2 of the total, respectively. The JEV RNA were detected from one pool of Culex mosquitoes and one pool of Ae. albopictus mosquitoes. The sequences of C/PrM genes of the 2 JEV strains were obtained. Homology and phylogenetic analyses showed that the 2 JEV strains are consistent with the genotypeⅠ(G-Ⅰ) and its clade of the same G-Ⅰ strains of JEV from GenBank, and the JEV strains from Jinghong were closely related to the JEV G-Ⅰ strains from Honghe prefecture of Yunnan in 2009, Dehong prefecture of Yunnan in 2010 and Gansu province, China in 2008. Mosquito samples tested negative for DENV in the study. Conclusion Existence of JEV G-Ⅰ in Jinghong city of Xishuangbanna prefecture was firstly confirmed from mosquitoes in 2015. It should be strengthened to monitor and control Japanese encephalitis epidemics in this area.

Objective To study the genetic polymorphism of clustered regularly interspaced short palindromic repeat (CRISPR)loci in the Yersinia pestis strains from Xinjiang Uygur Autonomous Region, China and then to identify the genotypes of tested strains. Methods Genomic DNA of 58 Y. pestis strains from Xinjiang was amplified using PCR technique, and the nucleic acid sequences of PCR production were then determined. On each CRISPR locus of every strain, spacers and spacer arrays were analyzed according to the PCR production sequences. Genotypes of tested strains were identified through the dendrogram generated by software. Results A total of 42 spacers and 23 spacer arrays were confirmed and 58 Y. pestis strains were divided into 16 genotypes. Yersinia pestis strains of genotype 3, 8, 11 and 16 distributed intensively in Wuqia county, Hotan prefecture, Nilka county and Manasi county respectively; strains of genotype 7 were all isolated from Rhombomys opimus and parasitic fleas in vitro in Junggar Basin; strains of the other genotypes mainly distributed in North Tianshan and Junggar Basin. Conclusion The genetic polymorphism of CRISPR loci in Xinjiang Y. pestis strains is high, and the geographical distribution of Y. pestis strains of different genotypes has obviously regional characteristics.

Objective To understand the mutations of Yersinia pestis, all of strains isolated in Tibet during 2009 to 2011 were selected to identify the biochemical features of the pathogen. Methods Traditional methods like glycerol fermentation, glucose metabolism and nitrate reduction were carried out. Tested strains isolated from Tibet during the year of 2009 and 2011, were incubated in biochemical action tubes made recently in 28℃ for 14 d, and the color of every tubes was observed and recorded each day. Results All of 111 tested strains were able to reduce nitrate and ferment glycerol, but unable to catabolize rhamnose; Nine of tested strains were capable of catabolizing arabinose, six of them isolated from Naqu and the other three from southern valley of the Qinghai-Tibet Plateau; The results of arabinose metabolism of the other 102 strains were all negative. Conclusion It was suggested that all tested strains belong to Biovar Antiqua. Those Y. pestis strains isolated from Naqu located in the northern Tibet were Qinghai-Tibet Plateau Ecotype, and most strains isolated from southern valley of the Qinghai-Tibet Plateau were Gangdise Mountain Ecotype except only three strains, which had the same biochemical features as the strains of Qinghai-Tibet Plateau Ecotype. It needs to utilize molecular methods through analyzing genetic markers to type the three special Y. pestis strains.

Objective To investigate the rodents species diversity along the border area of China and Kazakhstan, and provide supporting data for the surveillance and control of rodent borne diseases. Methods Rodents were collected with trapping method at seven counties/districts and area in Yili, Boertala, Tacheng and Karamay. Rodents species were then identified with DNA barcodes. Results Totally 174 samples of small mammal were collected from three kinds of habitats, including 16 species of rodents belonging to Muridae, Cricetidae, Dipodidae, Gliridae and Sciuridae, and one shrew species of Soricidae. With the DNA barcoding method, samples belonging to two vole species(Microtus arvalis and M. gregalis) with similar morphologic characters were identified correctly. Gerbil samples recognized morphologically as Meriones meridianus were different genetically from M. meridianus from Eastern China. Conclusion High diversity of rodent species were found in alpine forests meadows and desert steppe habitats. The genetic distances between M. meridianus from northern Xinjiang and other areas of China are so profound that suggests there are cryptic species.

Objective To assess the risk of flies in major industries of Nanchang city, and take measures to control the density of flies at low levels. Methods The invasion of flies in major industries was investigated by method of GB/T 23796-2009. To evaluate the risk of flies in major industries, classification standard of the risk occurrence possibility was established by Delphi method. Results The results of infestation in 2008-2010 showed that flies were likely to do impact people in industries of farm product markets, small restaurants, small foodstores, food processing industry, the station. Flies may possiblly do harm to people in hotels, supermarkets, canteens, tea and dance halls, hospitals. The risk levels have a downward trend in 5-10 month of 2011. To October, there were no risk possibility in industries of hospital (including hospitals), farmers market, enterprises; fixed-point stadiums, hotels, large and medium sized catering site still exists the risk possibility. Conclusion Through environmental, physical and chemical control measures, the density of declined during the period of 7th national intercity games, but some industries still had infestation risks. So it is necessary to take scientific measures to control flies in order to protect the public health.

Objective To understand the resistance of Blattella germanica in five areas of Shaanxi province and provide instruction to the use of insecticides. Methods Residual film method. Results The resistance index of field-collected strains of B. germanica were 1.08-3.69 to acephate, 1.04-4.10 to DDV, 1.30-9.69 to cypermethrin, 1.77-5.40 to beta- cypermethrin, 1.67-4.05 to deltamethrin, 1.28-9.74 to propoxur. Conclusion Insecticides should be applied scientifically to manage the increase in insecticidal resistance of B. germanica effectively.

Objective To study the ecotype and molecular characteristics of Yersinia pestis strain that was first isolated from Batang county of Sichuan, China and to provide scientific evidence for developing suitable strategy of plague control and prevention in Batang. Methods Traditional biochemical phenotype identification method and multi-locus variable number tandem repeats analysis (MLVA) were both chosen to identify ecotype and genotype of the tested strain. Traceability analysis was also performed. Results Yersinia pestis strain of Batang was capable of fermenting glycerine, arabinose and maltose, but not rhamnose. Nitrate reduction test of this strain was positive. The MLVA-type of tested strain was the same as Qinghai - Tibet Plateau Ecotype Y. pestis strains isolated from Qinghai province and Tibet Autonomous Region. Conclusion The ecotype of tested strain is Qinghai-Tibet Plateau Ecotype. It has closest relationship with Y. pestis strains distributed in both Qinghai and Tibet. Batang County of Sichuan is a newly discovered natural plague epidemic focus.

Objective To develop a simple genotyping method for rapid differentiation of Yersinia pestis strains between Microtus and non-Microtus biotypes. Methods Specific primers were designed and applied to amplify the aspartase gene (aspA) through polymerase chain reaction (PCR) among 93 Y. pestis strains of diverse origins and biotypes. The PCR products were genotyped by restriction fragment length polymorphism (RFLP) analysis using the restriction enzyme Hpy CH4Ⅳ. Genetic polymorphisms of aspA were determined by direct DNA sequencing. Results Among the 93 test strains, the amplified products of aspA digested with Hpy CH4Ⅳ showed two genotypes: Microtus biotype strains (38) all had two RFLP bands in sizes of 101 and 126 bp, respectively; and non-Microtus biotype strains (58) consistently had one single RFLP band in size of 227 bp. Direct sequencing data confirmed that mutation at the recognition site for restriction enzyme led to differences in the RFLP banding patterns. Conclusion A new genotyping method (aspA-PCR-RFLP) was established for rapid differentiation of Y. pestis strains between Microtus biotype with low virulence and non-Microtus biotype with high virulence according to different RFLP banding patterns. The proposed method can be used for epidemiologic surveillance in plague foci.

Objective To develop a simple genotyping method for rapid differentiation of Yersinia pestis strains between Microtus and non-Microtus biotypes. Methods Specific primers were designed and applied to amplify the aspartase gene (aspA) through polymerase chain reaction (PCR) among 93 Y. pestis strains of diverse origins and biotypes. The PCR products were genotyped by restriction fragment length polymorphism (RFLP) analysis using the restriction enzyme Hpy CH4Ⅳ. Genetic polymorphisms of aspA were determined by direct DNA sequencing. Results Among the 93 test strains, the amplified products of aspA digested with Hpy CH4Ⅳ showed two genotypes: Microtus biotype strains (38) all had two RFLP bands in sizes of 101 and 126 bp, respectively; and non-Microtus biotype strains (58) consistently had one single RFLP band in size of 227 bp. Direct sequencing data confirmed that mutation at the recognition site for restriction enzyme led to differences in the RFLP banding patterns. Conclusion A new genotyping method (aspA-PCR-RFLP) was established for rapid differentiation of Y. pestis strains between Microtus biotype with low virulence and non-Microtus biotype with high virulence according to different RFLP banding patterns. The proposed method can be used for epidemiologic surveillance in plague foci.

Objective To identify and classify newly-recorded rodent species in the epidemic focus of plaque in Dingbian county, Shaanxi province. Methods Morphological observation and DNA barcode technology were applied for rodent identification and classification. Results A total of 6 voles were captured with the body length between 120 mm and 140 mm, body weight ranging from 41.75 g to 71.58 g and skull length less than 32 mm. The tail length exceeded one third of the body length. The voles were covered by dark brown skin but their abdomen was sand-yellow in colour. The COⅠgene extracted from the samples was amplified through PCR and sequenced, with the maximum genetic distance between these samples and those of Microtus fortis from other areas being 1%. Conclusion The voles captured from the salt marshes in the southern edge of Ordos Plateau in the plague area of Dingbian county are identified as M. fortis through morphological analysis and DNA comparision. M. fortis is recorded for the first time in the plague natural foci of Shaanxi province, which provides useful information and a basis for further monitoring of vetor, plaque and related diseases in the area.

Objective To investigate the community density and carrying status of flies to inform the related control strategies in Kalamay. Methods Cage traps were deployed to monitor fly density. Captured flies were anesthetized, counted and identified. Colony count, coliform and pathogens were detected in accordance with the National Standard Test Method (GB/T 4789-2003). Results The average density of flies was 9.6 per cage in the area. The dominant species was Musca, which accounted for 57.0 % of the total captures, while Lucilia accounted for 30.9% and Sarcophaga for 9.1%. Colony count, yeast and fungi and coliform were respectively 4.3×10⁵ CFU, 1.2×10⁵ CFU and 973 MPN per fly. Conclusion Despite low density, the flies in Kalamay are carrying a wide range of microorganisms, including a number of conditioned pathogens.

Fleas are an important vector, and the Xenopsylla genus plays an important role in the spread of plague in China. This study describes the defining characteristics, geographical distribution, plague host and association of seven Xenopsylla species, providing the basis for the research and development of control strategies regarding the Xenopsylla genus.

Objective To determine the association between carboxylesterase (CarE) and beta - cyfluthrin resistance in Musca domestica in various habitats, and monitor this resistance at an early phase by using carboxylesterase. Methods Biological assessment was conducted using dripping titration and the activity of carboxylesterase was determined by the Asperen method. Results Except for the population in transfer stations, the three populations of M. domestica in residential areas, restaurants and farmer's market presented different resistance levels to beta-cyfluthrin with resistance ratios of 1.84, 15.31, 3.19 and 8.84, respectively. The CarE activities in the three populations were significantly elevated (P＜0.05), while 75%, 54% and 72% of them showed remarkably high activities, respectively. Overlapping susceptible strains were found in the three populations except for that in transfer stations. Conclusion Increased CarE activitiy was associated with beta-cyfluthrin resistance in M. domestica. The distribution of high CarE-activity strains showed that the populations in those areas were hybrid resistant strains, which was consistent with the bioassay Results. Based on this finding, it is advisable to restrict the use of beta-cyfluthrin in residential areas and use other pesticides as an alternative to avoid or defer the occurrence of resistance and apply this agent with caution in other habitats.