Objective:To understand the plague epidemic characteristics in the natural foci of the Qilian Mountains-A-erh-chin Mountains Himalayan marmot plague in Gansu Province, and to provide scientific basis for innovative prevention and control of the plague in combination with local conditions. Methods:A retrospective study was used to collect the monitoring data of the natural foci of plague in Gansu Province from 2011 to 2018 (from the epidemic surveillance files of the Center for Disease Control and Prevention of Gansu Province and direct network reporting information). Descriptive epidemiological method was used to analyze the plague epidemic characteristics of natural foci of the Qilian Mountains-A-erh-chin Mountains Himalayan marmot plague in Gansu Province from 2011 to 2018, including the distribution of host animals, pathogenic and serological testing of the plague bacteria, and the epidemic characteristics of human plague. Results:From 2011 to 2018, the total average marmot density in the natural foci of the Qilian Mountains-A-erh-chin Mountains Himalayan marmot plague in Gansu Province was 0.21/hm 2, of which Tianzhu County had the highest average marmot density of 0.58/hm 2, and Jiayuguan City had the lowest average marmot density of 0.01/hm 2. A total of 381 strains of Yersinia pestis were isolated in the foci, of which 4 were isolated from human corpses, 298 were host animals, and 79 were infectious vectors. Among them, the top 3 counties (cities) of isolated strains were Aksai County (38.85%, 148 strains), Subei County (31.50%, 120 strains) and Yumen City (16.27%, 62 strains). A total of 6 860 marmot serum, 1 769 dog serum were tested, the F1 antibody positive rates were 2.70% (185/6 860), 8.42% (149/1 769); and the F1 antigen positive rate of 814 animal materials was 4.30% (35/814), respectively. There were 4 times of human plague, 4 cases occurred and 4 cases died; 3 times occurred in Subei County and 1 time in Yumen City. The onset months were July, September, November and December. Active contact with infected animals such as shepherd dogs was the main route of infection, and migrant herders were the key occupation population. Conclusions:The animal epidemic situation in the natural foci of the Qilian Mountains-A-erh-chin Mountains Himalayan marmot plague in Gansu Province is active, and the plague presents different epidemic states in different regions. The prevention and control measures should be taken according to local conditions and guided by classification to strictly prevent the occurrence and transmission of the plague.

Objective To investigate the differences of X-ray findings of skeletal fluorosis between coal-burning type endemic fluo-rosis and industrial fluorosis.Methods The patients were randomly selected as research objects including 60 cases of coal-burning type endemic osteofluorosis and 60 cases of industrial osteofluorosis.The X-ray findings on the left forearm,crus and pelvic radio-graphs of these patients were analyzed retrospectively to find out the differences between skeletal fluorosis of coal-burning type endemic fluorosis and industrial fluorosis.Results X-ray features are no significant statistical differences between coal-burning type endemic fluorosis and industrial fluorosis,except these of interosseous membrane ossification of forearm and crus (forearmχ2=10.909,P<0.05;crusχ2=8.547,P<0.05),obturator membrane ossification of pelvis (χ2=36.554,P<0.05),periosteal proliferation outside bone of crus (χ2=4.937,P<0.05),and ossification of soleus (χ2=4.904,P<0.05).Conclusion The X-ray signs of endemic osteofluorosis and industrial skeletal fluorosis are almost similar,but there are some differences between them.

Plague natural foci in Gansu Province are large in area and widely distributed, and the epidemic status is different in each focus. Some plague natural foci have been resting for many years and are under stable control. In other plague natural foci, the epidemic of plague among animals is relatively active, and dozens of strains of Yersinia pestis can be isolated every year. The plague among animals spreads to the humans from time to time, and the cases of human plague are more severe, short in course of disease, and high in mortality. In recent years, with the sharp increase of migrant workers engaged in grazing and engineering construction in plague natural foci, opportunities to actively contact infected animals such as marmots, hares and sheepdogs have increased, resulting in an increase of human plague cases. In addition, the behaviors of illegal hunting, trafficking and sale of marmots cannot be stopped, resulting in human plague throughout the year. Therefore, the party committees and governments at all levels and the health administrative departments in Gansu Province have formulated the plague prevention and control measures suitable for this region according to the epidemic characteristics of plague among animals and humans. In this paper, the characteristics of plague epidemic situation at present and the prevention and control measures adopted in Gansu Province are discussed, in order to provide scientific basis and guidance for optimizing plague prevention and control measures in the future.

Objective:To study the genotyping and regional distribution characteristics of Yersinia pestis by single nucleotide polymorphism (SNP) in Gansu Province. Methods:A total of 52 strains of Yersinia pestis isolated from Himalaya Marmot plague foci and Spermophilus alaschanicus plague foci in Gansu Province from 1962 to 2017 were selected for culture and extraction of DNA. The genomic DNA of Yersinia pestis was sequenced by the second generation of Illumina PE150 to identify the SNP sites. The species characteristics of Yersinia pestis in Gansu Province was determined by the Kimura-2-parameter model of neighbor joining of Mega 10.0 software based on the SNP sites. The molecular evolutionary tree of the groups was determined by Hasegawa-Kishino-Yano model of maximum likelihood method according to the SNP sites. Results:A total of 103 SNP sites were identified in 52 strains of Yersinia pestis in Gansu Province, including 28 intergenic loci, 43 non-synonymous mutations, 31 synonymous mutations and 1 nonsense mutation. The 52 strains of Yersinia pestis were divided into 2 biotypes and 3 groups, which were ancient type (1.IN2, 3.ANT) and medieval type (2.MED). Among them, 35 strains belonged to 1.IN2 group, 13 strains belonged to 3.ANT group, and 4 strains belonged to 2.MED group. The 1.IN2 group was further divided into 5 subgroups: the groups of Yuerhong Town and Dangchengwan Town in Subei County, the groups of Mati Town and Dahe Town in Sunan County, and the group of Xiahe County. The 3.ANT group was further divided into 2 subgroups: the groups of Hongliuwan Town in Aksay County and Machang in Dangchengwan Town of Subei County. Conclusion:The SNP method can be used to genotype Yersinia pestis from different plague foci in Gansu Province, which has certain regional characteristics.