Epidemiologic analysis on Tibetan sheep plague from 1975 to 2005 in Qinghai Province

Abstract

Objective To analyze the epidemiologic feature of Tibetan sheep plague from 1975 to 2007 in Qinghai Province to provide a scientific basis for the prevention and control. Methods This study retrospectively summarized and analyzed the outcome of the surveillance on the plague prevalence and human plague profile from 1975 to 2007 in Qinghai Province. Results During 1975 - 2007, 14 strains of Yersinia pestis was isolated in Tibetan sheep, 10 from Yushu County, 2 from Nangqian County, 1 from Zhiduo County and 1 from Delingha City; In 1975 and in 1979, 4 strains of Yersinia pestis was isolated, 1996-2007 a total of 10; Tibetan sheep as a source of infection caused 10 times of human plague and 25 cases of plague, 13 died, with the incidence of 3,2,2,2 and 1 distributing in Yushu, Maduo, Nangqian, Zaduo and Maqin County, respectively, the case numbers of 6,6,8,4,1 respectively, and death toll 4,4,1,4,0. No plague cases were found in other counties(cities). Clinically, these 25 cases were known as 9 cases of glandular plague, 6 cases of pneumonic plague, 3 cases of septicemia plague, 1 cases of intestinal plague and 6 cases of secondary plague cases. In the 25 cases, 24 were Tibetan nomads except for 1 Han Chinese farmer, 20 of whom infected due to having peeled the skin or ate meat of sheep died of plague, 5 cases had contacted with patients with the disease. The months from June to November was the period of high incidence, with 11 cases of morbidity in November. Conclusions Since 1996, Tibetan sheep plague has begun to prevail consistently along with Marmota baibacina plague, with outburst seen in ranches in some regions. Over the past 10 years, it has not caused human plague, but its possibility of spreading to human remains. Therefore, timely and effective treatment and control of Marmota plague, as well as the increase of the awareness in Herdsmen of prevention and self-protection is a key to prevent the spread of the plague from sheep to human. Key words: Plague; Epidemiology; Sheep