Investigation and analysis of two suspected Yunnan sudden unexplained death cases in a village with a history of Yunnan sudden unexplained death / 中华地方病学杂志

Objective:To explore the cause of death of 2 suspected Yunnan sudden unexplained death (YNSUD) cases in Dayao County, Yunnan Province.Methods:The field epidemiological investigation and autopsy of 2 cases of YNSUD in Dayao County from June 15 to 20, 2020 were conducted; and blood and tissue samples were collected for qualitative analysis of common poisons and drugs.Results:The areas where the two cases were located were all seriously ill villages with a history of YNSUD, and the time of death occurred in the onset season of YNSUD. There was no blood relationship between the 2 cases, no obvious abnormal symptoms before death, no special diet, no history of exposure to pesticides and other toxic chemicals, and the test results of common poisons were all negative. Autopsy pathological examination results showed that case 1 died of acute cardiac dysfunction caused by sudden acute myocardial infarction of coronary heart disease, and case 2 died of central respiratory and circulatory failure caused by spontaneous subarachnoid hemorrhage.Conclusions:The two cases are excluded from YNSUD through autopsy, and the cause of death is determined. It is suggested that emergency response should be taken as soon as possible for YNSUD cases, and autopsy should be actively carried out to clarify the cause of death from a pathological point of view.

Improvement of the caf1 based PCR method for detection of the plague / 中华地方病学杂志

Objective To identify the causes of nonspecific bands in the detection of a industry standard caf1 gene by polymerase chain reaction(PCR),and to propose a solution to this problem. Methods A total of 112 strains were selected for the experiment, including 40 strains of Yersinia pestis, 72 strains of non-Yersinia pestis;DNA was extracted,and caf1 gene was amplified by PCR;seven non-specific strips were recovered,purified and TA cloning and sequencing; the primer of the caf1 gene was redesigned and validated using all of the strains. Results Using the industry standard caf1 gene primer,DNAs of 40 Yersinia pestis and 72 non-Yersinia pestis were amplified by PCR, 58 non-Yersinia pestis could be amplified with non-specific bands, they were about 400, 500, 600, 700, 800, 900, 1 000 bp. By TA cloning and sequencing, the non-specific bands in the downstream of the industry standard caf1 primer and its reverse complement were amplified. Using the new designed caf1 primer to amplify, 72 non-Yersinia pestis strains showed no non-specific bands. Conclusion Non-specific bands has been amplified in the screening of Yersinia pestis using the primer of the industry standard caf1, and the new caf1 primer can effectively avoid this problem and improve the accuracy of detection.

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 relationship between natural disasters and plague / 中华地方病学杂志

“There are big epidemics after natural disasters”.After years of analysis of the relationship between natural disasters and plague in Yunnan Province,we found that plague occurred with high frequency during the flooding period,and rodent's density and flea index were higher in years of flooding than those of normal years.However,each disaster event such as flooding,drought or earthquakes was not necessarily connected with rodents density,index of fleas and plague prevalence.The density of host animals and the index of vector were mainly determined by climatic factors such as air temperature,rainfall (humidity) and so on.Natural disasters will damage the local living environment,which caused the aggregation of host animals and humans.Close contacts between host animals and humans will promote the risk of epidemic spreading in the active plague foci.

Geographical distribution of host animals of plague in residential areas in Yunnan Province / 中华地方病学杂志

Objective To investigate the geographical distribution of plague host animals in residential areas and the association between plague and its distribution pattern in Yunnan Province.Methods A systematic investigation on fauna and community ecology of rodents was carried out in residential areas of 17 counties(cities) of Yunnan Province,southwestern China with different longitude,latitude and elevation from May 2007 to November 2012.The characteristics of the spatial distribution of flea communities along environmental gradients were analyzed using community structure indexes.Results A total of 390 small mammals were trapped in seventeen counties (cities),and the mammals were classified into 11 species and 7 genus in 4 families.Among all small host mammals,Rattus tanezumi,Rattus nitidus and Rattus norvegicus were dominant species of host animals in residential areas,accounting for 33.85％ (132/390),20.77％ (81/390) and 16.92％ (66/390),respectively.The horizontal distribution of rodents showed that Rattus tanezumi was the widest species in residential areas,which was found at the longitude 98°-105°,followed by Rattus norvegicus,Rattus yunnanensis and Mus musculus.The vertical and latitudinal distributions of rodents were similar in residential areas.Rattus tanezumi was also the widest distributed species,which was observed at the latitude 21°-＜ 28°N and at the altitude 500-＜ 3 500 m; the constituent of Rattus tanezumi showed similar trends of leaning peak curves,first gradually increasing and then decreasing with the increase of latitude and elevation; Rattus tanezumi gradually changed into Rattus nitidus and Apodemus chevrieri,et al.The richness spatial distribution patterns of host animals showed similar trends of leaning peak curves which gradually increased and then decreased with increasing of longitude and latitude; the highest richness was observed at the longitude 98°-＜ 101°E and at the latitude 23°-＜ 28°N.While,the richness spatial d istribution patterns of host animals were relatively poor in the low or the high altitude range.The highest richness was observed at the altitude between 1 000-＜ 1 500 m and 2 000-＜ 2 500 m.Conclusions All spatial patterns of indoor host animals have shown an aggregated spatial distribution in Yunnan Province.Moreover,important environmental factors such as longitude,latitude,and altitude play a substantial role on the distribution patterns of indoor host animals among various focus,therefore directly impact on the modes of prevalence and transmission of plague.