Characters Of Yulong Yersinia Pestis Strains From Yunnan Province, China

In 2005, five human cases of primary pneumonic plague were reported in Yulong County in Yunnan province of China and resulted in two deaths. Several Yersinia pestis strains (designated Yulong strains) have been isolated from rats and fleas in this area since 2006, and a new plague focus in Yulong County has been confirmed. However, the source of these Yulong strains and their relationship with strains from nearby natural foci remain unclear. In this study we compared Yulong strains with previously isolated strains from Yunnan province by biochemical analysis, clustered regularly interspaced short palindromic repeats (CRISPR) and pulsed-field gel electrophoresis (PFGE) methods which revealed significant differences between the Yulong strains and early Y. pestis strains. However, the Yulong strains were found to be similar to Himalayan marmot strains. Therefore, Yulong strains are a new type of Y. pestis in Yunnan province and likely represent the first step in the transmission of Yersinia pestis from the Qinghai-Tibet Plateau to Yunnan province. The Yulong focus merits greater attention because of its special status of Yunnan plague epidemiology.