Objective:To investigate the infection status of Yersinia in the main host animals of plague in Xiahe and Luqu counties, the Himalayan marmot plague foci of Gansu Province, and to provide a basis for exploring the epidemic status of plague in these foci. Methods:Samples of the ileocecal region and contents, pharyngeal swabs (or tongue roots), and blood of the main host animals of plague in Xiahe County and Luqu County where the plague were active in the 1950s and 1960s were collected from 2014 to 2018. The Yersinia isolation, virulence determination and F1 antibody detection were performed, respectively. Results:Totally 24 strains of Yersinia were detected in 958 samples of ileocecal region and contents with a bacterial detection rate of 2.51%, which were 13 strains of Yersinia enterocolitia (Y.e), 1 strain of Yersinia kristensenii (Y.k), 2 strains of Yersinia frederiksenii/ intermedia (Y.f/i), 6 strains of Yersinia intermedia (Y.i), 1 strain of Yersinia aldouae (Y.a) and 1 strain of Yersinia massiliensis (Y.m). Totally 19 strains of Yersinia were detected in 958 samples of pharyngeal swabs (or tongue roots), and the detection rate was 1.98%, which were 8 strains of Y.e, 1 strain of Yersinia pseudotuberculosis (Y.p), 4 strains of Y.k, 1 strain of Y.f/i, 4 strains of Y.i, and 1 strain of Yersinia ruckeri (Y.r). The virulence types of 21 strains of Y.e were ail -ystA -ystB +yadA -virF -rfbc -, ail -ystA -ystB -yadA -virF -rfbc -, respectively, accounting for 9.52% (2/21) and 90.48% (19/21), none were pathogenic. The results of F1 antibody in 1 079 serum samples were all negative. Conclusions:Yersinia are widely found in the pharynx and intestines of the main host animals of plague in Xiahe and Luqu counties, and the Y.e detected are all non-pathogenic strains. The results of this investigation can provide clues for further study on the preservation of Yersinia pestis in host animals and their living environment.

Objective:To study the epidemic situation of Marmota himalayana plague and Yersinias infection in Yugur Autonomous County of Sunan (Sunan County) of Gansu Province, and to provide new ideas for prevention and control of plague. Methods:From 2014 to 2018, liver and spleen, cecum, throat swabs and blood samples of Marmota himalayana were collected on the spot in Sunan County, where Yersinia strains were isolated and identified, and plague F1 antigen and antibody were detected. Results:A total of 634 liver and spleen samples, 427 cecum samples and 426 throat swabs samples were collected from Marmota himalayana, and 23 strains of Yersinia pestis, 2 strains of Yersinia marcescens, and 1 strain of Yersinia flexneri were detected, with the detection rates of 3.63% (23/634), 0.47% (2/427) and 0.23% (1/426), respectively. The detection rate of Yersinia pestis in different years was statistically significantly different (χ 2 = 13.19, P = 0.010). A total of 1 822 serum samples of Marmota himalayana were detected, and 5 F1 antibody positive samples were detected, with a positive rate of 0.27%, the difference of positive rate between different years was statistically significant (χ 2 = 25.22, P < 0.001); 282 liver and spleen tissue homogenates of Marmota himalayana were detected, 22 F1 antigen positive samples were detected, the positive rate was 7.80%, and there was no statistically significant difference between different years (χ 2 = 7.85, P = 0.097). The 23 strains of Yersinia pestis detected were distributed in Mati Tibetan Township (12 strains), Dahe Township (6 strains) and Qifeng Tibetan Township (5 strains); 1 strain of Yersinia flexneri and 2 strains of Yersinia marcescens were both located in Dahe Township. Conclusion:There is an epidemic of plague among animals in Sunan County from 2014 to 2018, and the areas where Yersinia pestis and non pathogenic Yersinia are detected overlapped.