RESUMO
Objective:To study the basic situation of Yunnan Province Suncus murinus carrying plague phage and to explore its epidemiological significance. Methods:From 2015 to 2018, a survey of plague host animals was carried out in 10 investigation sites in the historical plague foci, new plague foci (after 1982) and stubborn plague foci of domestric mouse in Yunnan Province. The plague phage was isolated and cultured from the intestinal specimens of Suncus murinus. The growth of plaque was observed by double-layer plate method, and the morphology and structure of plague phage were observed under electron microscope. At the same time, intestinal samples were taken to detect the structural gene caf1 of F1 antigen of Yersinia pestis. Results:In this study, a total of 157 Suncus murinus were captured and 16 strains of plague phage were isolated, with a total isolation rate of 10.19%. There was no difference in plague phage isolation rate between historical plague foci (10.00%, 1/10) and stubborn plague foci (16.22%, 12/74), new plague foci (4.11%, 3/73, χ 2 = 0.00, P = 0.965; Fisher test, P = 1.000). However, there was a difference in plague phage isolation rate between stubborn plague foci and new plague foci (χ 2 = 5.88, P = 0.015). There was no significant difference in the isolation rate of plague phage among different sex, growth period and habitat ( P > 0.05). The plaque morphology of the isolated plague phage was diverse, of which four strains were myotavirus phages; and all samples were negative for F1 antigen structural gene caf1. Conclusions:Suncus murinus is widely distributed in the domestic mouse plague foci in Yunnan Province, and the animals carry a certain number of plague phage. Regular surveillance of Suncus murinus and their plague phage has a certain guiding significance for the surveillance and early warning of plague in Yunnan Province.
RESUMO
Objective:To explore the biochemical characteristics, virulence factors and other phenotypes of the strains of Yersinia pestis isolated in Jianchuan County Yunnan Province in 2017, and to analyze the nature and source of the new plague epidemic. Methods:Three strains of Yersinia pestis (JC109 rat, JC109 fleas and JC113) isolated from Daqing Village, Jinhua Town, Jianchuan County, Dali Prefecture, Yunnan Province in 2017, and 2 associated strains of Yersinia pestis (LJ01 in Yulong County, Lijiang City and LJ04 in Gucheng District of Lijiang City), 5 control strains ( Yersinia pestis JC1332, LJ485, BN2636, EV-76 and Yersinia pseudotuberculosis PST-1), preserved by the Central Laboratory of Yunnan Institute for Endemic Disease Control and Prevention were collected. The biochemical characteristics and ecotypes of Yersinia pestis were analyzed by using arabinose, rhamnose, denbiose, maltose and glycerol fermentation experiments and nitrate reduction experiments. Combining pigmentation factor (pgm), virulence antigen (VW) detection and nutritional requirements test results to determine the virulence of Yersinia pestis. Results:The Yersinia pestis JC109 rat, JC109 fleas and JC113 all fermented arabinose, maltose and glycerol, but didn't ferment rhamnose and denbiose; and the nitrate reduction test was positive. The ecological type belonged to the Himalayan Marmot plague strain of Qinghai-Tibet plateau. The virulence factors pgm and VW tests were positive, the nutritional requirement type was phenylalanine dependent and glutamate independent. It had the same phenotype as the LJ01 strain, but different from the JC1332 strain. Conclusions:The newly isolated strains in Jianchuan County are the same as those in the Lijiang Yulong wild rodent plague foci. This outbreak may have been imported from the Lijiang Yulong wild rodent plague foci to the south.