title: [The epidemiology and etiology research of Tibetan sheep plague in Qinghai plateau].
abstract: OBJECTIVE
  To identify the epidemiology and etiology characteristics of Tibetan sheep plague in Qinghai plateau.
  
  
  METHODS
  The background materials of Qinghai Tibetan sheep plague found during 1975 to 2009 were summarized, the regional, time and interpersonal distribution, infection routes, ecological factors for the spread were used to analyze; followed by choosing 14 Yersinia pestis strains isolated from such sheep for biochemical test, toxicity test, virulence factors identification, plasmid analysis, and DFR genotype.
  
  
  RESULTS
  From 1975 to 2009, 14 Yersinia pestis strains were isolated from Tibetan sheep in Qinghai province. Tibetan sheep, as the infection source, had caused 10 cases of human plague, 25 plague patients, and 13 cases of death. All of the initial cases were infected due to eating Tibetan sheep died of plague; followed by cases due to contact of plague patients, while all the initial cases were bubonic plague. Cases of bubonic plague developed into secondary pneumonic plague and septicemia plague were most popular and with high mortality. Most of the Tibetan sheep plague and human plague occurred in Gannan ecological zone in southern Gansu province, which was closely related to its unique ecological and geographical landscape. Tibetan sheep plague coincided with human plague caused by Tibetan sheep, especially noteworthy was that November (a time for marmots to start their dormancy) witnesses the number of Yersinia pestis strains isolated from Tibetan sheep and human plague cases caused by Tibetan sheep. This constituted the underlying cause that the epidemic time of Tibetan sheep plague lags obviously behind that of the Marmot plague. It was confirmed in the study that all the 14 strains were of Qinghai-Tibet Plateau ecotype, with virulence factors evaluation and toxicity test demonstrating strains as velogenic. As found in the (Different Region) DFR genotyping, the strains isolated from Yushu county and Zhiduo county were genomovar 5, the two strain isolated from Nangqian county were genomovar 5 and genomovar 7, while those isolated Delingha region were genomovar 8.
  
  
  CONCLUSIONS
  Tibetan sheep were vulnerable to plague infection, hence causing human plague as the infectious source. The Yersinia pestis strains isolated from Tibetan sheep plague carried pathogen characteristics of Qinghai-Tibet plateau plague, developing many new characteristics of such plague.
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Baiqing
authors.initials: B
authors.lastname: Wei
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Haoming
authors.initials: H
authors.lastname: Xiong
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Yonghai
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Meiying
authors.initials: M
authors.lastname: Qi
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Jin
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Youquan
authors.initials: Y
authors.lastname: Xin
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Hanqing
authors.initials: H
authors.lastname: Yang
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China.
authors.forename: Xiumin
authors.initials: X
authors.lastname: Han
authors.affiliation: Department of Plague Prevention and Control, Qinghai Institute for Endemic Diseases Prevention and Control, Xining 811602, China; Email: drx200907@163.com.
authors.forename: Ruixia
authors.initials: R
authors.lastname: Dai
mesh_terms: D000818:Animals; D004463:Ecology; D005838:Genotype; D005843:Geography; D006801:Humans; D008392:Marmota; D010930:Plague / Q000453:epidemiology* / Q000662:veterinary; D010957:Plasmids; D012756:Sheep / Q000382:microbiology*; D018609:Tibet / Q000453:epidemiology; D015010:Yersinia pestis