Objective　To understand the situation of plague host vectors, indicator animals and residents infected with plague bacteria in Cangyuan County, Yunnan Province, China-Myanmar border region, and to explore the risk of plague epidemic, so as to provide reference basis for supplementary plague data and prevention and control in this area. Methods　A plague survey was carried out in three townships in Cangyuan County in 2023. The collected host animals organs and body surface parasitic fleas were bacterial cultured. Serum collected from border residents, indicator animals, and host animals was tested for plague F1 antibodies using indirect hemagglutination assay (IHA). The positive samples were rejudged by IHA, immune colloidal gold assay(GICA) and up-converting phosphor technology(UPT). Results　Totally 294 serum samples were collected from border residents, with an average age of (48.48±14.27) years old, with more females than males. Three were positive for F1 antibody against Yersinia pestis, with a positive rate of 1.02%. And 65 samples of indicator animal serum and 31 samples of Rattus tanezumi serum were collected, and the detection of plague F1 antibody was negative. And 198 rodents belonging to 3 orders, 5 families, 11 genus and 14 species were captured, with a total capture rate of 7.93%, with Rattus tanezumi (46.97%) and Rattus andamanensis (19.19%) as the dominant species. The capture rate in residential indoor areas was 3.72%, and Rattus tanezumi was the absolutely dominant species (100.00%). The capture rate in farming areas was 10.26%, the dominant species were Rattus tanezumi (36.36%), Rattus andamanensis (23.03%), Mus pahari (10.30%) and Hylomys suillus (10.30%). And 60 fleas belonging to 3 families, 5 genera and 6 species were seized, the average infection rate of fleas was 11.62%, and the total flea index was 0.30. The dominant species were Xenopsylla cheopis (28.34%), Palaeopsylla remota (23.33%), Ctenophthalmus quadratus (18.33%), Stivalius aporus (15.00%) and Palaeopsylla incurua (11.67%). A total of 198 murine organ samples were isolated and cultured, and 24 groups of flea samples were obtained, no Yersinia pestis was isolated. Conclusion　The investigation has not found any recent infection with Yersinia pestis in rodents, body surface parasitic fleas and indicator animals; however, it is found that there is still a certain proportion of positive population of plague F1 antibody in the serum of residents. Rattus tanezumi and Xenopsylla cheopis are the first dominant species of host and vector in the county, the indoor density of Rattus flavipectus exceeds 3%, reaching the animal pestis IV early warning, and there is a risk of recurrence in the plague foci.

This study was aimed at understanding the Babesia species makeup and distribution in small mammals in Jinsha River Basin of Yunnan Province,and the Babesia carriage status in small mammals in this area,to provide a scientific basis for the preven-tion and control of Babesia disease.A total of 1 493 small mammals belonging to 5 orders,10 families,25 genera,and 54 species were captured from 10 counties(cities)in the Jinsha River Basin of Yunnan Province in various agricultural and forest environments.DNA was extracted from liver and tick tissues,and 150 bp fragments of Babesia 18S rRNA were detected through molecular biological methods.The positive samples showed amplification of a 1 600 bp target fragment of 18S rRNA.Species characteristics were assessed through sequence comparison and phylogenetic analysis.A total of 14 small mammals infected with Babesia were detected in six coun-ties(cities)of Jinsha River Basin,Yunnan Province,with a positivity rate of 0.93%(14/1 493).The Otsu and Kobe types of Babesia voles were analyzed,and their sequences were compared with the sequences from human Babesia cases with high similarity and close evolutionary relationships.The positivity rates were 2.34%(3/128)in Qiaojia County,2.06%(2/97)in Yongshan County,1.88%(4/213)in Yuanmou County,1.03%(3/291)in Deqin County,0.95%(1/105)in Shangri-La City,and 0.78%(1/128)in Shuifu County.The positive small mammals belonged to one order,two families,six genera,and the following eight species:P.leucurus 5.56%(1/18),R.brunneusculus 3.36%(4/119),M.minutus 3.33%(1/30),E.custos 2.94%(1/34),N.confucianus 2.65%(3/113),N.fulvescens 2.35%(2/85),A.latronum 1.16%(1/86),and A.draco 0.98%(1/102).The detection of Babesia in M.minutus was re-poorted first time.Small animals infected with Babesia were detected in all three habitats and altitudes,and higher infection rates were observed in forest regions between 1 500 and 2 500 meters and high-altitude residential areas.Babesia infection was found in many small mammals in several counties(cities)along Jinsha River in Yunnan Province,and the epidemic status of Babesia in these areas warrants attention.

Objective:To investigate the host and vector composition of pestis and the epidemic situation of pestis among animals in the border port areas of Longchuan County, Yunnan Province.Methods:In September 2022, a survey was conducted on rodents and their surface parasitic fleas in the border port areas of Longchuan County, according to three habitat types: residential areas, agricultural areas, and forest-shrubbery areas. Samples of murine animals organs and their surface parasitic fleas were collected for isolation and identification of Yersinia pestis. Blood samples of plague indicating animals, such as murine animals, dogs and cats were collected, and serum plague F1 antibody was detected by indirect hemagglutination assay. Meanwhile, a retrospective investigation was conducted on the occurrence of self dead rats, sick rats, and suspected cases in the local area from 2018 to 2022 through interviews with farmers. Results:A total of 168 murine animals belonging to 3 orders, 5 families, 10 genera, and 11 species were captured in three habitats in Longchuan County. Among them, the capture rate in residential areas was 5.00% (30/600), with Rattus tanezumi and Suncus murinus as dominant species, with a composition ratio of 50.00% (15/30). The capture rate in agricultural areas was 9.67% (122/1 262), with Rattus tanezumi and Suncus murinus as dominant species, with a composition ratio of 50.82% (62/122) and 44.26% (54/122), respectively. The capture rate in the forest-shrubbery areas was 6.25% (16/256), with Hylomys suillus and Eothenomys eleusis as dominant species, with a composition ratio of 37.50% (6/16) and 31.25% (5/16), respectively. Among the captured murine animals, 20 individuals carried 52 parasitic fleas, belonging to 2 species of 2 genera and 2 families. The total flea infection rate was 11.90% (20/168), and the total flea index was 0.31 (52/168). The dominant specie was Xenopsylla cheopis (90.38%, 47/52). The flea infection rate in residential areas was 33.33% (10/30), and the flea index was 1.23 (37/30). The flea infection rate in agricultural areas was 7.38% (9/122), and the flea index was 0.11 (14/122). The flea infection rate in the forest-shrubbery areas was 6.25% (1/16), and the flea index was 0.06 (1/16). The samples of murine animals and their parasitic fleas obtained were isolated and cultured by Yersinia pestis, and the results were negative. A total of 144 serum samples from murine animals, dogs and cats were separated, and no F1 antibody against pestis was detected. According to interviews and investigations, no abnormal situations such as a large number of self dead rats, sick rats, and suspected cases were found from 2018 to 2022. Conclusions:No plague epidemic has been found in the border port areas of Longchuan County recently. The main host of plague, Rattus tanezumi, and the main vector, Xenopsylla cheopis, remain the dominant species in this area.

This study was aimed at understanding the Babesia species makeup and distribution in small mammals in Jinsha River Basin of Yunnan Province,and the Babesia carriage status in small mammals in this area,to provide a scientific basis for the preven-tion and control of Babesia disease.A total of 1 493 small mammals belonging to 5 orders,10 families,25 genera,and 54 species were captured from 10 counties(cities)in the Jinsha River Basin of Yunnan Province in various agricultural and forest environments.DNA was extracted from liver and tick tissues,and 150 bp fragments of Babesia 18S rRNA were detected through molecular biological methods.The positive samples showed amplification of a 1 600 bp target fragment of 18S rRNA.Species characteristics were assessed through sequence comparison and phylogenetic analysis.A total of 14 small mammals infected with Babesia were detected in six coun-ties(cities)of Jinsha River Basin,Yunnan Province,with a positivity rate of 0.93%(14/1 493).The Otsu and Kobe types of Babesia voles were analyzed,and their sequences were compared with the sequences from human Babesia cases with high similarity and close evolutionary relationships.The positivity rates were 2.34%(3/128)in Qiaojia County,2.06%(2/97)in Yongshan County,1.88%(4/213)in Yuanmou County,1.03%(3/291)in Deqin County,0.95%(1/105)in Shangri-La City,and 0.78%(1/128)in Shuifu County.The positive small mammals belonged to one order,two families,six genera,and the following eight species:P.leucurus 5.56%(1/18),R.brunneusculus 3.36%(4/119),M.minutus 3.33%(1/30),E.custos 2.94%(1/34),N.confucianus 2.65%(3/113),N.fulvescens 2.35%(2/85),A.latronum 1.16%(1/86),and A.draco 0.98%(1/102).The detection of Babesia in M.minutus was re-poorted first time.Small animals infected with Babesia were detected in all three habitats and altitudes,and higher infection rates were observed in forest regions between 1 500 and 2 500 meters and high-altitude residential areas.Babesia infection was found in many small mammals in several counties(cities)along Jinsha River in Yunnan Province,and the epidemic status of Babesia in these areas warrants attention.

Objective:To investigate the host and vector composition of pestis and the epidemic situation of pestis among animals in the border port areas of Longchuan County, Yunnan Province.Methods:In September 2022, a survey was conducted on rodents and their surface parasitic fleas in the border port areas of Longchuan County, according to three habitat types: residential areas, agricultural areas, and forest-shrubbery areas. Samples of murine animals organs and their surface parasitic fleas were collected for isolation and identification of Yersinia pestis. Blood samples of plague indicating animals, such as murine animals, dogs and cats were collected, and serum plague F1 antibody was detected by indirect hemagglutination assay. Meanwhile, a retrospective investigation was conducted on the occurrence of self dead rats, sick rats, and suspected cases in the local area from 2018 to 2022 through interviews with farmers. Results:A total of 168 murine animals belonging to 3 orders, 5 families, 10 genera, and 11 species were captured in three habitats in Longchuan County. Among them, the capture rate in residential areas was 5.00% (30/600), with Rattus tanezumi and Suncus murinus as dominant species, with a composition ratio of 50.00% (15/30). The capture rate in agricultural areas was 9.67% (122/1 262), with Rattus tanezumi and Suncus murinus as dominant species, with a composition ratio of 50.82% (62/122) and 44.26% (54/122), respectively. The capture rate in the forest-shrubbery areas was 6.25% (16/256), with Hylomys suillus and Eothenomys eleusis as dominant species, with a composition ratio of 37.50% (6/16) and 31.25% (5/16), respectively. Among the captured murine animals, 20 individuals carried 52 parasitic fleas, belonging to 2 species of 2 genera and 2 families. The total flea infection rate was 11.90% (20/168), and the total flea index was 0.31 (52/168). The dominant specie was Xenopsylla cheopis (90.38%, 47/52). The flea infection rate in residential areas was 33.33% (10/30), and the flea index was 1.23 (37/30). The flea infection rate in agricultural areas was 7.38% (9/122), and the flea index was 0.11 (14/122). The flea infection rate in the forest-shrubbery areas was 6.25% (1/16), and the flea index was 0.06 (1/16). The samples of murine animals and their parasitic fleas obtained were isolated and cultured by Yersinia pestis, and the results were negative. A total of 144 serum samples from murine animals, dogs and cats were separated, and no F1 antibody against pestis was detected. According to interviews and investigations, no abnormal situations such as a large number of self dead rats, sick rats, and suspected cases were found from 2018 to 2022. Conclusions:No plague epidemic has been found in the border port areas of Longchuan County recently. The main host of plague, Rattus tanezumi, and the main vector, Xenopsylla cheopis, remain the dominant species in this area.

Objective:To study the epidemic characteristics of human brucellosis in Yunnan Province, and to provide a reliable scientific basis for formulating accurate prevention and control strategies of brucellosis.Methods:The epidemic data of human brucellosis in Yunnan Province from January 2019 to December 2021 were collected from the information system of the China Center for Disease Control and Prevention, as well as annual monitoring data on brucellosis reported by various states (municipalities) in Yunnan Province. Descriptive epidemiological methods were adopted to analyze the epidemic situation, distribution characteristics (time, region, population), and serological and pathogenic monitoring results of brucellosis.Results:From 2019 to 2021, 1 408 cases of brucellosis were reported in Yunnan Province, with an average annual incidence of 1.00/100 000. The number of cases increased from 321 in 2019 to 701 in 2021, and the incidence increased from 0.68/100 000 in 2019 to 1.50/100 000 in 2021. The onset time was mainly from April to September (857 cases). The top 3 regions with the highest number of reported cases were Kunming City (483 cases), Qujing City (379 cases), and Honghe Hani and Yi Autonomous Prefecture (281 cases), accounting for 81.18% (1 143/1 408) of the total number of cases. The age of onset was mainly 20 - < 70 years old, accounting for 89.70% (1 263/1 408). There were 958 males and 450 females, with a sex ratio of 2.13 ∶ 1.00. Farmers were the main occupation, accounting for 84.02% (1 183/1 408). From 2019 to 2021, a total of 26 280 serum samples from key populations of brucellosis were monitored in Yunnan Province, with 572 positive serological tests and a positive rate of 2.18% (572/26 280). A total of 169 strains of Brucella were isolated from blood samples from hospitals throughout the province, including 155 strains of sheep type 3 and 14 strains of sheep type 1. Conclusions:From 2019 to 2021, the incidence of human brucellosis in Yunnan Province has been on the rise, with a high incidence in summer and autumn. The main population affected is young and middle-aged male farmers. Therefore, it is necessary to strengthen disease monitoring and health education for key populations during the high incidence season.

Objective:To study the basic situation of Yunnan Province Suncus murinus carrying plague phage and to explore its epidemiological significance. Methods:From 2015 to 2018, a survey of plague host animals was carried out in 10 investigation sites in the historical plague foci, new plague foci (after 1982) and stubborn plague foci of domestric mouse in Yunnan Province. The plague phage was isolated and cultured from the intestinal specimens of Suncus murinus. The growth of plaque was observed by double-layer plate method, and the morphology and structure of plague phage were observed under electron microscope. At the same time, intestinal samples were taken to detect the structural gene caf1 of F1 antigen of Yersinia pestis. Results:In this study, a total of 157 Suncus murinus were captured and 16 strains of plague phage were isolated, with a total isolation rate of 10.19%. There was no difference in plague phage isolation rate between historical plague foci (10.00%, 1/10) and stubborn plague foci (16.22%, 12/74), new plague foci (4.11%, 3/73, χ 2 = 0.00, P = 0.965; Fisher test, P = 1.000). However, there was a difference in plague phage isolation rate between stubborn plague foci and new plague foci (χ 2 = 5.88, P = 0.015). There was no significant difference in the isolation rate of plague phage among different sex, growth period and habitat ( P > 0.05). The plaque morphology of the isolated plague phage was diverse, of which four strains were myotavirus phages; and all samples were negative for F1 antigen structural gene caf1. Conclusions:Suncus murinus is widely distributed in the domestic mouse plague foci in Yunnan Province, and the animals carry a certain number of plague phage. Regular surveillance of Suncus murinus and their plague phage has a certain guiding significance for the surveillance and early warning of plague in Yunnan Province.

ObjectiveTo analyze the community structure and dynamics of parasitic fleas on the body surface of host animals and nested fleas in different seasons in the natural foci of wild rat plague in Yulong County，Yunnan Province， to explore the relationship between seasonal fluctuation of fleas and the prevalence of plague among animals， so as to provide evidence for plague prevention and control in the natural foci. MethodsNanxi Village， Huangshan Town， the core area of plague epidemic in Yulong County， was selected as the monitoring sample area in December 2019 （winter）， August 2020（summer）， October 2020（autumn） and March 2021（spring）. Host animals were captured by rattrap at night and rat nests were excavated for collecting parasitic fleas on host animals and rat nest fleas in different seasons. Excel 2010 and SPSS 26.0 software were used to analyze the data， and Chi square test was used to compare the rate. Community ecological indicators were used to analyze the community structure and species diversity of the host animals and their parasitic fleas. ResultsA total of 355 vector fleas were captured， belonging to 7 species of 5 genera in 2 families. 441 small animals were captured and 138 rat body fleas were detected with the flea infection rate of 14.51% and the flea index 0.31. 96 effective rat holes were excavated and 217 fleas were detected with the flea infection rate of 35.42% and the flea index 2.26. Among the four seasons， the flea infection rates of rat body and rat nests were higher in summer and winter， showing a significant difference in general （χ²=15.851， P<0.01； χ²=16.398， P<0.01）. The dominant species of flea community were Ctenophthalmus quadratus， Stenischia humilis， Neopsylla specialis and Frontopsylla spadix， with a dominance index of 0.434， 0.254， 0.180 and 0.110， respectively. The diversity and evenness of rat body fleas showed a distribution characteristic of decreasing， increasing and then decreasing again with season changes， and both were the highest in spring， while the ecological dominance showed an opposite trend. The diversity and evenness of rat nest fleas showed a distribution characteristic of increasing first and then decreasing in summer， autumn and winter， with the highest in autumn， while the ecological dominance was diametrically opposite. ConclusionThe fleas community structure is relatively stable in Yulong County， but the number of species in the community is unevenly distributed by seasons， and the status of dominant species is prominent. Local authorities should carry out timely preventive deratization and depulization measures according to the results of daily monitoring， so as to effectively avoid the prevalence and spread of plague among animals in plague foci.

Objective:To investigate and determine the epidemic scope of plague natural foci in Yulong County of Yunnan Province, and to assess its epidemic risk, so as to providing basis for monitoring, prevention and control of plague.Methods:In 2017, 2 - 3 natural villages were selected from 8 villages and towns in Yulong County according to geographical landscape, altitude, population and area. During October and November, small mammal hosts and their parasitic fleas were captured by the night trap (cage) method, Yersinia pestis was isolated from host animal organs, and plague F1 antigen and antibody were detected by colloidal gold test. Plague specific antigen was detected by reverse indirect hemagglutination test (RIHA) in self-dead small mammals. Animal serum from dogs, cats and mice were collected for detection of plague F1 antibody by indirect hemagglutination test (IHA). Results:A total of 1 019 host animals including self-dead small mammals were collected, belonging to 22 species, 12 genera, 6 families, 4 orders. Among them, 1 016 small mammals were captured by tools and 996 were outdoors, with the capture rate of 25.28% (996/3 940). The dominant species of small mammals outdoors were Apodemus chevrieri, Rattus (R.) rattus, Eothenomys miletus and Crocidura attenuate, which accounted for 30.32% (302/996), 22.09% (220/996), 17.37% (173/996) and 12.35% (123/996). The common species were Niviventer confucianus, R.nitidus and R.norvegicus, which accounted for 8.13% (81/996), 4.02% (40/996) and 1.81% (18/996). A total of 20 small mammals of 9 species were captured indoors in the residential area, and the capture rate was 1.11% (20/ 1 800). The dominant species were R.norvegicus, R.nitidus and Mus musculus, which accounted for 30.00% (6/20), 25.00% (5/20) and 10.00% (2/20). Eighteen small mammals of 8 species were infected with 67 parasitic fleas, belonging to 5 species, 5 genera, 3 families. The total flea infection rate was 1.77% (18/1 019) and the total flea index was 0.070. Among them, 49 parasitic fleas from 4 small mammals of 3 species were collected indoors. The flea infection rate was 19.05% (4/21) and the flea index was 2.333. Leptopsylla segnis had the highest flea infection rate of 9.52% (2/21) and flea index of 0.571. Ctenocephalides felis had the highest flea index of 1.571 and flea infection rate of 4.76% (1/21). They were the main flea species on the body surface of small mammals in residential areas. There were 14 small mammals infected with parasitic fleas outdoors, and 18 fleas in 5 species were collected with flea infection rate of 1.40% (14/998) and flea index of 0.018. Among them, Leptopsylla segnis had the highest flea infection rate was 0.50% (5/998) and the flea index was 0.005. The flea infection rate of Neopsylla specialis specialis was 0.40% (4/998), and the flea index was 0.004. Ctenophthalmus quadratus had the highest flea index of 0.007, and the flea infection rate ranked the third with 0.30% (3/998). The flea infection rate and flea index of Frontopsylla spadix spadix were the lowest, which were 0.20% (2/998) and 0.002, respectively. Ctenophthalmus quadratus, Leptopsylla segnis and Neopsylla specialis specialis were the dominant parasitic fleas on the surface of outdoor small mammals. A total of 419 indicator animal sera were collected, including 402 dog sera. One of them was positive by IHA, with a positive rate of 0.25% (1/402). Seventeen serum samples were collected from cats and mice, and IHA test results were negative. Yersinia pestis was isolated and cultured from the organs of small mammals and the detection of Yersinia pestis by colloidal gold test was negative. RIHA test of self-dead small mammals was negative. Conclusion:A plague indicator animal positive spot is newly found in the plague natural foci in Yulong County, and the plague epidemic monitoring, prevention and control in this region should be strengthened.

Objective:To investigate whether the squirrels in Yunnan Province carried Yersinia pestis phages and their epidemiological significance. Methods:From 2015 to 2018, plague host animals were investigated in five of Yunnan plague foci and non-plague foci. The spleen, liver and intestinal specimens of the squirrels captured in the investigation were taken and stored at low temperature for later use. Intestinal specimens with PBS solution, were filtered by 0.22 μm and added to LB liquid medium containing 100 μl suspension of plague vaccine strain (EV76) and then oscillated in a constant temperature gas bath at 28 ℃ and 220 r/min for 18 to 24 h. The double-layer plate method was used to isolate and observe the growth of plaque. The morphology and structure of Yersinia pestis phages were observed under electron microscope. Meanwhile, spleen, liver and intestinal specimens were taken for detection of Yersinia pestis specific marker gene caf1. Results:A total of 10 squirrels were captured (8 Callosciurus erythraeus and 2 Dremomys pernyi), and four Yersinia pestis phages were isolated (2 in Callosciurus erythraeus and 2 in Dremomys pernyi). Two were isolated from non-plague foci (Yongshan County), two from house rats plague foci (Mile County and Xinping County), and none was isolated from wild radents plague foci (Jianchuan County and Eryuan County). By naked eye observation, two bacteriophages from the plague foci produced transparent plaques and grew well, while two bacteriophages from non-plague foci produced translucent plaques and with poor growth. By electron microscopy, these Yersinia pestis phages were of typical Myoviridae family, their head diameter was about 40 nm, muscle tail was about 120 nm, and tail filament cluster was slightly visible at the end of muscle tail. And all the 10 samples of squirrels were negative of plague-specific caf1 gene. Conclusions:The proportion of plague phages carried by Yunnan squirrels is relatively high. Although the detection of caf1 is negative. Squirrels may be a carrier of plague transmission due to the existence of Yersinia pestis phages.