Objective To investigate the species composition, quantitative distribution, and seasonal variation of rodents and their parasitic fleas in the Zhangjiakou 2022 Winter Olympic Games zone (hereinafter referred to as the Zhangjiakou competition zone) and the surrounding areas in Hebei province, China, and to provide basic data for the prediction and emergency treatment of vector-borne diseases during the Winter Olympic Games. Methods From September 2018 to September 2019, the five-meter traping method and the quadrat method were used to investigate the species composition and density of rodents in Chongli district and the area around the Zhangjiakou competition zone, and parasitic fleas were collected and classified. The ecological method was used to analyze the species composition, distribution, and seasonal density variation of rodents, and Excel 2010 software was used to analyze data and draw charts. Results The quadrat method was used to investigate 20 quadrats, and no rodents were captured. The five-meter traping method was used to investigate 166 sites, and 266 rodents were captured by 16 600 traps and were classified into 8 species, 5 genera, and 3 families, with a capture rate of 1.60%. Time variation showed a rodent density of <1.00% from October to June in the next year, especially from December to April in the next year. Apodemus agrarius and Cricetulus barabensis were the main rodent species, and the rodent density was 6.14% in July and 5.93% in September. There was a variety of rodent species, mainly A. agrarius, C. migratorius, C. barabensis, A. peninsulae, and A. draco. A total of 266 rodents were examined, among which 36 were found to have fleas, with a flea infestation rate of 13.53%, and a total of 100 fleas were collected and classified into 7 species, 5 genera, and 3 families, with a mean flea index of 0.38. Bacteriological and serological tests were performed for all materials and yielded negative results. Conclusion Main host animals and fleas in Hebei province and surrounding natural plague foci are not found in the Zhangjiakou competition area and the surrounding area, and there are differences in natural landscape, the species composition of rodents, and the composition of fleas between the Zhangjiakou competition zone and natural plague foci in Hebei province. Therefore, there is a relatively low risk of primary animal plague in the local area.

Objective To compare the effects of two common ecological niche models, maximum entropy (Maxent) and genetic algorithm for rule-set production (GARP), in prediction of the potential risk areas of epizootic plague. Methods Logistic regression was used to screen for climate and environment-related risk factors for the epizootic situation of Meriones unguiculatus. The Maxent and GARP models were independently used to predict the potential distribution of epizootic plague in M. unguiculatus. Results The following factors were screened out and significantly associated with epizootic plague in M. unguiculatus (P<0.05):elevation, seasonal variation in air temperature, the highest temperature in the hottest month, mean temperature of the driest quarter, mean temperature of the coldest quarter, annual precipitation, precipitation of the wettest quarter, precipitation of the hottest quarter, mean precipitation in February, mean precipitation in May, mean precipitation in August, and mean precipitation in September. The areas under the receiver operating characteristic curves (AUCs) for the training set and test set of the Maxent model were 0.989 and 0.987, respectively. AUCs for the training set and test set of the GARP model were 0.961 and 0.958, respectively. According to the Maxent model, the potential risk areas of epizootic plague accounted for 89.45% of the total area of the foci of M. unguiculatus plague, and the moderate-to-high risk areas accounted for 86.63% of the total area. The GARP model predicted that the potential and moderate-to-high risk areas accounted for 96.43% and 48.57% of the total area, respectively. Conclusion Both ecological niche models have good performance for accurately and reliably predicting the potential risk areas of the epizootic situation of M. unguiculatus plague. The Maxent model has more accurate prediction, while the GARP model predicts a larger spatial extent. Selection of predictive models can be made according to actual needs.

Objective To investigate the genotypes and genetic characteristics of Yersinia pestis strains isolated from Kangbao county in Hebei province, China in 2017. Methods The DNA of three Y. pestis strains isolated from Kangbao county in Hebei province in 2017 was extracted by boiling method and kit extraction method. According to the literature, the primers of 22 different regions (DFRs) and pMT1 were synthesized and the DFR sites were amplified by PCR. The genotype was analyzed after agarose gel electrophoresis. Results The DFRs in the three strains were DFR02-05, DFR08-11, DFR14, DFR19-22, and pMT1, but not DFR01, 06, 07, 12, 13, and 15-18. The genotype was G20 after alignment. Conclusion The genotype of Y. pestis isolated from the plague foci in Hebei province in 2017 is G20 and different from G17 isolated previously. The emergence of new genotype provides a basis for further study of the genetic characteristics and epidemiological characteristics of the strain.

Objective To study the changes of Spermophilus dauricus number and distribution in Hebei province plague natural foci. Methods Investigate the plague surveillance data from 2007 to 2016 of plague natural foci in Hebei province, and statistically analyze the density, quantity change and distribution of S. dauricus in different habitats, analyze the results via rank sum test. Results A total of 1 086 hectares of plague natural foci in Hebei province were investigated over a decade, with 7 082 cloth clips, 794 rodents, with an average density of 0.73 per hm². Spermophilus dauricus had the highest density in the three habitats of woodland, hillside and grassland, which were 0.86/hm², 0.85/hm², and 0.83/hm², respectively. Conclusion The density of S. dauricus does not change much from year to year, and the population is relatively stable. Woodland, hillside, grassland are the most suitable habitats for S. dauricus.

Objective To explore the epidemic factors of animal plague in Hebei province, China, and provide scientific basis for the prevention and control of plague. Methods The materials were collected and rodents were tested by "four step test" of plague, and the fleas were tested by group method or single stomach pulling method. Results A total of 240 358 rodents were tested, and 123 positive plague materials were found. Five of 14 856 vectors tested positive for Yersinia pestis. There were 7 animal plague prevalent years in Hebei province. Conclusion The prevalence of animal plague epidemic occurred intermittently in plague natural foci of Hebei province, the main change of hosts was a primary cause of animal plague, especially the gerbil density in animal plague epidemic years.

At the initial stage of epidemics, the bacteria of plague natural foci were more virulent, nitrogen removal was stable, and the plasmid species were relatively complete and stable. But at the end of the epidemic, the virulence of the plague was weaker, nitrogen removal was not stable, and plasmids tended to be absent. There were great differences in the morphology of plague bacteria in nature. Biological, biochemical, plasmid and virulence of Yersinia pestis were investigated in Hebei province, China. The mechanism of the existence of plague was revealed in some way.

Objective To study the genotype and epidemiological characteristics of Yersinia pestis in Hebei foci. Methods Primers were designed according to the confirmed 22 different segments (DFR), to genotype the 116 Y. pestis DNA of Hebei province. Results All of the strains lack these DFR of 01, 06, 07, 13, 15-18, to compare the genetic typing system of DFR, Y. pestis from Hebei province belong to the 17 genotype, distributed in the northern Kangbao county neighboring Huade, Baiqi, and Taipusiqi in the Inner Mongolia Autonomous Region. Conclusion The Y. pestis is stable genetically in Hebei plague foci, and have only one genotype, so the epidemic tends to stabilize.

Plague is an enzootic infectious disease. The rodent animals are primary reservoir hosts of plague. There are 223 kinds of animal which have been found to be infected with plague in nature. Plague-tolerant animals which can be naturally infected with plague without symptoms serve as plague-indicators. These animals also play a very important role in the spread of the plague. The research of plague-indicating animals was reviewed in this paper which provides scientific basis for plague prevention and control in China.

Objective To evaluate enzyme immunostaining technique for detection of F1 antigen of Yersinia pestis in rodents. Methods Visceral organ specimens of 266 mice infected with virulent Y. pestis and 207 control rodent specimens were detected by horseradish peroxidase labeled plague F1 monoclonal antibody (HRP-F1McAb) enzyme immunostaining technique, and in comparison with the RIHA and RGICA methods．Results Coincidence was 98.52% between HRP-F1McAb enzyme immunostaining technique and RIHA, Kappa=0.970, and the difference was statistically significant in the positive detection rates (χ²=5.140, P=0.016); Coincidence was 98.50% between HRP-F1McAb enzyme immunostaining technique and RGICA, Kappa=0.901, with statistically insignificant difference in the positive detection rates (χ²=0.250, P=0.625). Sensitivity of HRP-F1McAb enzyme immunostaining technique was 100%, specificity was 97.02%, positive predictive value was 97.14%, negative predictive value was 100%, and Youden index was 0.970． Conclusion The enzyme immunostaining technique is sensitive and specific, fast and simple in detection of plague F1 antigen. It is a valuable detection technique in early and rapid diagnosis of plague in rodents．

Objective To study the genotype of Yersinia pestis in Hebei plague foci by variable number of tandem repeat (VNTR). Methods Primers were designed according to the confirmed 14＋12 VNTR, to genotype the 116 Y. pestis DNA of Hebei province. Results All of the strains showed one genetype, but they were different from CO92 and EV. Conclusion There is only one genetype of plague, indicating a genetic stability in Y. pestis in Hebei province.

The plague is categorized as a Class A infectious disease in China. Plague foci are widely distributed, and strains have different features and varied virulence in China. It is of great significance for deducing the sudden outbreak of plague and terrorist attack detection, with the strains of different foci for genotyping. The choice of tandem repeats loci is the key of the multiple loci vntr analysis (MLVA) classification results. This assay mainly introduces tandem repeats in Yersinia pestis genotyping in application progress, and provides a reference for other workers in genotyping.

Objective To characterize the genosome of 116 Yersinia pestis strains isolated from plague foci in Hebei province in China. Methods All the strains were detected by polymerase chain reaction (PCR) with 15 pairs variable number tandem repeat (VNTR) provided by China CDC, then the length of results were analyzed. Results The numbers and lengths of the repeat sequences from all strains are same with the single primer, and different with the different primers, such as the length of all stains with the prime M52 is 153 bp, and the number of the repeat sequences is 3, then with the prime M59, the length and the number is 250 bp and 3 respectively. Conclusion Multiple loci VNTR analysis (MLVA) genetic typing is reliable, and it is stable genetic mark of Y. pestis from Hebei province. To build the database of the plague with MLVA is useful for the investigation of the plague variation and source.

Objective To investigate the species, composition and infection with Yersinia pestis of parasitical fleas on Myospalax aspalax bodies and their role in the epidemic of rodent plague in Hebei province, providing a scientific basis for the better control of rodent plague. Methods Parasitical fleas on the bodies of M. aspalax were collected and classified with Y. pestis isolated. Results Nine species of fleas belonging to 7 genera and 3 families were found in the present study. No Y. pestis was isolated from the 111 M. aspalax and the cultures of 715 fleas in 68 groups by microbiological tests, with the Y. pestis specific antibody negative in 88 serum samples from M. aspalax. Conclusion There are a great number of fleas on the body of M. aspalax that can be infected with Y. pestis naturally, with Amphipsylla daea being the dominant parasitical flea, which may be involved in plague epidemics.

　　【Abstract】　Objective　To study  the  practicability  of  double  antigens  sandwich  enzyme  linked  immunosorbent  assay（DAgS?ELISA）on the detection of Yersinia pestis F1 antibodies. Methods　A total of 558 samples antibodies of anti?F1 antigen were detected by DAgS?ELISA and trace indirect hemagglutination assay (trace?IHA). Results　Thirty three samples were positive tested by IHA, 31 positive by DAgS?ELISA, the positive accordance rate was 90.91%, 99.81% for negative accordance rate, 99.28% for the total accordance rate. The positive rate detected by IHA and DAgS?ELISA were 5.91% and 5.56% respectively, and no statistics difference was found (χ2＝0.25，P＝0.625). About 27 the immuno?serum were positive detected by IHA and DAgS?ELISA methods, and the sensitivity of IHA test were all higher than that of DAgS?ELISA (t＝3.023, P＝0.006). Conclusion　Sensitivity of DAgS?ELISA is lower than that of trace?IHA, but its specificity is better and no primary inhibitory phenomena, and could exempt from leak detection in the preliminary screening.

　　【摘要】　通过对鼠疫常用血清学研究方法和发展历程的介绍，使鼠疫防治人员对鼠疫诊断技术有一个全面的了解。鼠疫血清学是20世纪50－60年代发展起来的免疫学方法，经过半个世纪的应用和研究，不断有新的方法出现。通过我们的介绍，为鼠疫工作者今后的鼠疫监测和鼠疫防治提供科学依据。

Objective To study the sensitivity of colloidal gold immunobinding and analyze the distribution of crowd bubonic plague F1 immune body in Hebei province.Methods 196 serums and 162 serums of healthy people were sampled from history areas affected by plague and plague foci among animals(Zhangjiakou city) in Hebei natural plague foci and fur processing workers in Baoding.100 serums were collected from non-plague foci as control.Colloedal gold immunobinding and indirect hemagglutination test(IHA) were used to detect,at the same time,the minimum limit of detection of these two methods was compared.Results There were 3 positive serums in 196 serum samples,and the positive rate was 1.53%.None positive samples was found in 162 serum samples.The control were all negative.Conclusion The minimum detection of colloedal gold immunobinding was less than that of IHA.There were positive serum samples in plague natural foci,and the people age whose serum presented positive exceeded 40 years old.The samples collected from Baoding fur processing workers and non-plague foci were all negative.2 samples were positive after vaccination by investigation,and others needed be further explored.

Objective To study the distribution of plague F1 antibody from coat-processor blood serum in the coat market of Li county, Baoding city. Methods To detect 162 blood serums sampled statistically from coat-processor with indirect hemagglutination assay(IHA) and colloedal gold immunobinding, and 63 blood serums collected from non coat-processor as control. Results 162 blood serums were all negative, accordant with the control. Conclusion There was no plague recessive in coat-processor from coat market of Li county, Baoding city.

Objective To study the three-dimensional distribution and maintenance mechanisms of plague F1 antibody of healthy population in the plague natural foci of Hebei province. Methods To sample 196 blood samples from three administrative villages belonging to plague natural foci formerly, and collect 100 blood samples from non-infected areas as the control. Indirect hemagglutination test(IHA) and colloedal gold immunobinding were used in this test. Results There were 4 positive among 196 blood samples, and the positive rate was 2.04%. There were 4 positive samples in IHA and 3 positive samples in colloedal gold immunobinding. The human serums collected from non-infected areas were all negative after tested by theses two methods. There was significant difference between the positive rate of F1 antibody in epidemic areas and the positive rate of F1 antibody in non-epidemic areas (χ₂=0.822,P<0.05). Conclusion At present, there are still a number of F1 antibody positive population in the natural epidemic focus of Hebei, and it needs further investigation and analysis to clarify.

Objective Plague animal material is tested by 4-pair-primer-PCR which is compaired with traditional “4 piece test” to find a quick diagnostic way for plague. Methods Narcotics test and 4-pair-primer-PCR are both done in traditional way. Results 52 positive specimen of 4-pair-primer-PCR are found from 150,and 62 of traditional way are found. Both the ways have no discrepancy(χ²=1.42,P> 0.05 ). Conclusion 4-pair-primer-PCR is a quick,peculiar,sensitive method for the diagnosis and surveillance of plague.