Investigation on the infection of spotted fever group Rickettsiae and Rickettsia mooseri of wild rodents in the field of plague foci in Western Yunnan / 中华地方病学杂志

Objective:To investigate the infection of spotted fever group Rickettsiae (SFGR) and Rickettsia mooseri ( R.mooseri) of wild rodents in the field of plague foci in Western Yunnan. Methods:The DNA of liver samples of 2 512 wild rodents captured from the plague foci in Lianghe County, Jianchuan County and Yulong County in Western Yunnan from 2015 to 2016 was extracted by magnetic bead method, and the heat shock protein groEL gene primers were used for nested PCR amplification. Gene sequence splicing and Blast homology comparison were performed using DNAStar 7.1 software and GenBank of the National Center for Biotechnology Information (NCBI) of the United States, respectively, and DNAStar 7.1 and MEGA 6.0 softwares were used to construct phylogenetic trees.Results:The wild rodents infected with SFGR were Mus pahari, Rattus steini, Crocidura attenuata and Suncus murinus (one for each), with a total infection rate of 0.16% (4/2 512); no R.mooseri infection was detected. The SFGR infection rates of wild rodents in the plague foci of Lianghe County and Jianchuan County were 0.49% (3/611) and 0.10% (1/1 029), respectively; no SFGR infection was detected in the wild rodents in the plague foci of Yulong County. The homology analysis showed that the homology between SFGR positive samples and reference sequences was 95.45%-100.00%; some of the groEL gene sequences were highly similar among the four positive samples, and the homology was 89.60%-97.40%. Sequence evolution analysis showed that the sequences of three SFGR positive samples from the plague focus in Lianghe County were clustered in the same branch, and the homology reached 94.40%-97.40%; one positive sample sequence from the plague focus in Jianchuan County was clustered in one branch. Conclusion:SFGR infection rate of wild rodents in the field of plague foci in Western Yunnan is low, and no R.mooseri infection is found.

Hepatitis E virus infection and gene polymorphism in murine-shaped animals of plague foci in Yunnan Province / 中华地方病学杂志

Objective:To learn about the infection and gene polymorphisms of hepatitis E virus (HEV) in murine-shaped animals of plague foci in Yunnan Province.Methods:From July to August 2019, around 16 natural villages (4 in Mile City, 6 in Mangshi and 6 in Lianghe County), which were the foci of domestic plague in Yunnan Province, the murine-shaped animals were captured by the night-time method. The liver RNA was extracted, and the target gene of rat HEV was detected by one-step real-time fluorescence quantitative PCR, and the positive rate of rat HEV was calculated. The rat HEV positive samples were amplified by PCR for further clone sequencing, and the resulting sequences were compared with the HEV sequences registered in the GenBank and a phylogenetic tree was constructed by using MegAlign and MEGA 7.0.Results:A total of 491 murine-shaped animals were captured from 3 orders, 5 families, 8 genera, 15 species, and the positive rate of rat HEV was 4.89% (24/491). Among them, the positive rate of Rattus tanezumi and Niviventer fulvescens was 9.39% (23/245) and 1/3, respectively; and other species were negative. There was a statistically significant difference in the positive rate of rat HEV between different habitats ( P = 0.014), and the positive rate of rat HEV in the habitats near the dwellings was higher than that in other habitats ( P < 0.05). The sequence comparison analysis showed that the gene sequence of P018 from Lianghe County was 100.0% homologous to the MG813927.1 sequence of the first patient with rat HEV in Hongkong, and it was clustered into the same branch with the sequences of MG813927.1 and LC549185.1 from rat, was the type HEV C. G024 from Mangshi shared a low homology (20.7% - 31.5%) with other virus strains, and it was clustered into the same branch with a HEV sequence from an avian (AY535004.1). Conclusions:Rat HEV is prevalent in murine-shaped animals of plague foci of Yunnan Province, and there may be gene polymorphisms of rat HEV. In addition, the difference infection rate may be related to the habitats.

Isolation and epidemiological significance of Yersinia pestis phages in indicator animals from the house mouse plague foci of Yunnan Province / 中华地方病学杂志

Objective@#To investigate whether plague phages were present in the indicator animals of plague foci in Yunnan Province, and to explore their epidemiological significance.@*Methods@#Anus swabs were collected from indicator animals (dogs or cats) of the 41 plague affected villages in 26 towns of 10 cities (counties, districts) of Yunnan plague foci from November of 2015 to March of 2018. The Yersinia pestis phages were isolated by plague vaccine strain EV76. The isolation of plague phages from different plague foci, the isolation of plague phages from different canine species (cats), the polymorphism of plaque and the host spectrum of phages were analyzed.@*Results@#A total of 1 014 indicator animals (1 003 dogs and 11 cats) were studied, and 102 of plague phages were isolated. In the 10 cities (counties, districts), plague phages were only not isolated from Lancang County, and the plague phages were isolated from the other 9 cities (counties, districts). The separation rates from high to low were as follows: Yiliang County (21.00%, 21/100), Menghai County (19.23%, 25/130), Yuanjiang County (11.63%, 10/86), Midu County (11.50%, 13/113), Wenshan County (10.10%, 10/99), Mile Country (7.07%, 7/99), Lianghe County (6.67%, 7/105), Baoshan Longyang District (4.90%, 5/102) and Gengma County (3.81%, 4/105). Of the 102 plague phages, 75 were isolated from the native dogs (Chinese pastoral dogs, 9.32%, 75/805), 20 from the pug dogs (13.70%, 20/146), 5 from the wolf dogs (17.24%, 5/29), 1 from Samoye (1/4) and 1 from Alaska dog (1/2). The plaque of the phage was divided by five appearance of complete lysis (the plate was clear), large (2.5-4.0 mm), big (1.5-< 2.5 mm), middle (0.5-< 1.5 mm) and small (< 0.5 mm). The representative phages were all of the Myoviridae family. Most of the phages could lysis the strains of Yersinia pestis, and some phages could lysis Shigella and type 5 Yersinia pseudotuberculosis (PST5).@*Conclusion@#The plague phages are present in the plague foci of Yunnan, and the phages are polymorphic.

Isolation and epidemiological significance of Yersinia pestis phages in indicator animals from the house mouse plague foci of Yunnan Province / 中华地方病学杂志

Objective To investigate whether plague phages were present in the indicator animals of plague foci in Yunnan Province,and to explore their epidemiological significance.Methods Anus swabs were collected from indicator animals (dogs or cats) of the 41 plague affected villages in 26 towns of 10 cities (counties,districts) of Yunnan plague foci from November of 2015 to March of 2018.The Yersinia pestis phages were isolated by plague vaccine strain EV76.The isolation of plague phages from different plague foci,the isolation of plague phages from different canine species (cats),the polymorphism of plaque and the host spectrum of phages were analyzed.Results A total of 1 014 indicator animals (1 003 dogs and 11 cats) were studied,and 102 of plague phages were isolated.In the 10 cities (counties,districts),plague phages were only not isolated from Lancang County,and the plague phages were isolated from the other 9 cities (counties,districts).The separation rates from high to low were as follows:Yiliang County (21.00％,21/100),Menghai County (19.23％,25/130),Yuanjiang County (11.63％,10/86),Midu County (11.50％,13/113),Wenshan County (10.10％,10/99),Mile Country (7.07％,7/99),Lianghe County (6.67％,7/105),Baoshan Longyang District (4.90％,5/102) and Gengma County (3.81％,4/105).Of the 102 plague phages,75 were isolated from the native dogs (Chinese pastoral dogs,9.32％,75/805),20 from the pug dogs (13.70％,20/146),5 from the wolf dogs (17.24％,5/29),1 from Samoye (1/4) and 1 from Alaska dog (1/2).The plaque of the phage was divided by five appearance of complete lysis (the plate was clear),large (2.5-4.0 mm),big (1.5-＜ 2.5 mm),middle (0.5-＜ 1.5 mm) and small (＜ 0.5 mm).The representative phages were all of the Myoviridae family.Most of the phages could lysis the strains of Yersinia pestis,and some phages could lysis Shigella and type 5 Yersinia pseudotuberculosis (PST5).Conclusion The plague phages are present in the plague foci of Yunnan,and the phages are polymorphic.

Community structure of wild myomorpha in the plague foci of Lianghe County, Yunnan Province / 中华地方病学杂志

Objective To investigate the community structure and spatial distribution of wild myomorpha in the plague foci of Lianghe County,Yunnan Province.Methods From December 2015 to October 2016,in Mangdong,Hexi,Nangsong and other places in Lianghe County,forest landscape samples were randomly selected in different altitude gradients (1 000 ～,1 200 ～,1 400 ～,≥ 1 600 m).Peanut was used as a bait for trapping myomorpha,and the community structure of myomorpha was analyzed.Results A total of 663 myomorpha were collected and the density was 7.97％ (663/8 320),which were divided into 16 species,11 genus,5 families,and 3 orders.Rattus tanezumi (30.62％,203/663) was the dominant species.In the 1 000-＜ 1 200 m altitude gradient,the richness of myomorpha was the highest (13 kinds).In the 1 400-＜ 1 600 m altitude gradient,the index of diversity (2.094 2) was the highest.With the increase of altitude,the ecological dominance were increased,and the values were 0.672 2,0.774 2,0.842 8,and 0.882 4,respectively,whereas the evenness presented a decreasing trend,and the values were 0.269 2,0.197 1,0.142 8,and 0.162 0.Conclusions The Rattus tanezumi has presented a single dominant distribution at different elevation and the number and the species of the wild rodent with superior position have increased with the altitude increased in Lianghe focus.With the increase of altitude,the diversity and the evenness have increased,whereas the richness and the dominance have decreased.

Mechanisms of persistence of Yersinia pestis in the foci / 中华地方病学杂志

Yersinia pestis,host animals and vector organisms in a particular area within a certain geographical landscape,and biological communities are in the form of interdependence and mutual restriction of ecological system in the plague natural foci of plague.Currently,the preservation of Yersinia pestis mechanism mainly including:①Animal and fleas (tick) preservation theory;②Yersinia pestis own mutation preservation theory;③Fleas-host-fleas preservation theory;④Theory of soil preservation;⑤the birds and abiotic factors of preservation theory;⑥Theory of other Yersinia preservation theory and so on.The author summarized the research progress of the preservation mechanism of Yersinia pestis in the focus area.

The epidemic situations of animal plague in the animal plague foci of Yinchuan City from 2004 to 2014 / 中华地方病学杂志

Objective To analyze the changes of gopher density and epidemic situations of animal plague in the natural plague foci of Yinchuan from 2004-2014,to sum up the epidemic regularity of the epidemic situation,and to provide a scientific basis for prevention and treatment of the plague.Methods Retrospective analysis was used in the study.The plague monitoring data were collected;the number of host animals,density of rat,media index,aetiological and serological test results were analyzed.Results From 2004 to 2014,a total of 15 664 rats in 14 species,4 families and 9 genera were captured.The dominant populations were Meriones unguiculatus and Meriones meridianus.The density of rats was 4 919 km2,the number of rats was 6 196,the density of each rat was 0.21 to 3.85/hm2,and the average density was 1.26/hm2.A total of 15 664 rats were examined,the number of positive rats was 33,and the positive rate was 0.21％ (33/15 664).Among them,gerbils were 29,accounted for 87.88％ (29/33);18 strains of Yersiniapestis were detected in dead rats,which accounted for 54.54％ (18/33).A total of 5 810 groups of 22 070 fleas were cultured,the number of positive fleas was 42,and the positive rate was 0.12％ (7/5 810).Plague fleas were 2 kinds,the same type cheopis subspecies in 6 groups of 37 fleas,Nosopsyllus laeviceps vole subspecies in 1 group of 5 fleas.The positive number of F1 antibody was 3,and the positive rate was 0.12％ (3/ 2 446).Conclusions Yinchuan City,the natural foci of plague epidemic,is in the active state.We should pay attention to the density changes of Meriones unguiculatus and strengthen the monitoring work to pick up the dead rats,and found the epidemic of animal plague as soon as possible,in order to prevent the occurrence of human plague.

Predictors for abundance of Rattus tanezumi in households of commensal rodent plague foci / 中华流行病学杂志

Objective To explore the predictors on the abundance of Rattus (R.) tanezumi in households of commensal rodent plague foci.Methods Thirty natural villages that experienced previous plague cases in Lianghe county,Yunnan province,were selected followed by random selection of 20 households in each village through computer technique.Live traps were set in households to capture small mammals which were then identified to species in the field according to their morphological features.Data on potential factors for abundance of R.tanezumi were collected through questionnaires and field observation and were coded and computerized using EpiData software and further analyzed by hurdle regression model under R software.Results A total of 166 rodents (133 R.tanezumi and 33 Suucus murinus) were captured.Results from final multilevel hurdle regression model showed that the likelihood of R.tanezumi captures increased by 1.67-to 2.76-fold in households belonged to Dai ethnic families that stored foodstuff in metal pails,often raising dogs,and having adjacent houses.The number of R.tanezumi captures increased by 2.18-fold in the villages where over 80％ of the households would raise chickens.In the villages with communal latrine,the likelihood and the number of R.tanezumi capture increased 1.93-fold and 2.38-fold,respectively.While the likelihood of R.tanezumi captures would reduce by 45％-61％ in those households where there were cats and cattle being raised and maize grown in the village.The number of R.tanezumi captures would reduce by 63％ in the households where there were outside toilets.Conclusion The abundance of R.tanczumi seemed to be closely related to the ecological environment factors.Programs on plague control and prevention should relate to ecological factors that influencing the abundance of R.tanezumi.

Ecological-geographic landscapes of natural plague foci in China Ⅶ.Typing of natural plague foci / 中华流行病学杂志

Objective To group and characterize natural plague foci in China.Methods A novel two-class typing method as well as a three-indication nomenclature method were established to group and characterize the natural plague foci,on the basis of eco-geographical landscapes of plague foci,genetics of Yersinia pestis,zoology of rodent reservoirs and the entomology of flea vectors.Results A total of 12 distinct natural plague foci (including 19 subtypes) as well as their biological features were characterized.Conclusion Natural plague foci in China were grouped and characterized in this study.

Eco-geographic landscapes of natural plague foci in China Ⅰ.Eco-geographic landscapes of natural plague foci / 中华流行病学杂志

Objective To study the eco-geographic landscapes of natural plague foci,in China.Methods According to the surveillance records on plague epidemics and the eco-geographic landscapes of natural plague foci based on the county level,the criterion for classifying the ecological geographic zone of Chinese natural plague foci was established.Results 12 types and 19 subtypes of eco-geographic landscapes on Chinese natural plague foci were identified.Conclusion Scientific basis for Chinese natural plague foci classification was provided.

Fleas notified on Microtus fuscus foci in Sichuan province / 中华流行病学杂志

Objective To analyzed the variant information on the indices regarding fleas from natural foci of Microtus plague in Sichuan epidemic area during 2000 to 2008.Methods Statistical and analytical methods were used on the surveillance data regarding Microtus fuscus plague.Results There were 19 flea species identified and the share of Callopsylla sparsilis was 62.79 percent while the share of Amphipsylla tuta tuta was 30.90 percent on Microtus fuscus plague.The infection rate of fleas and the flea index were the highest in October and the lowest in December and March.Species as Callopsylla sparsilis,Amphipsylla tuta tuta and Rhadinopsylla dahurica vicina could naturally infect the Yersinia pestis.Conclusion Microtus fuscus plague could become epidemic when animals and flea species were infected.We should emphasis on plague monitoring program so as to prevent the occurrence of the disease.