Isolation of Yersinia pestis phage from Rattus norvegicus in Yunnan province and its epidemiological significance

ObjectiveTo investigate the status of plague phages in Rattus norvegicus, the host animal of plague in Yunnan province, and to explore its epidemiological significance.

MethodsFrom 2015 to 2018, samples were taken from 25 sites in 10 counties and cities of Yunnan province to collect intestinal specimens of captured Rattus norvegicus. The Yersinia pestis phage was isolated from intestinal specimens by double plate method. The specific gene caf1 of Yersinia pestis was detected.

ResultsTotally 344 copies of brown mouse were collected and 15 strains of Yersinia pestis phages were isolated from them, with a total isolation rate of 4.36%. From the sampling points, 10 spots were isolated from Yersinia pestis phages, with the highest isolation rates of Chunhe street and Yudai street in Hongta district of Yuxi city (28.57% and 16.67%). There was no significant difference between the sex, age and habitat of rats on the isolation of Yersinia pestis phages.The caf1 test of all specimens was negative. Four of the isolated bacteriophages are of the Myoviridae family.

ConclusionThere are a certain number of Yersinia pestis phages in Rattus norvegicus in Yunnan province, and they are distributed in the historical epidemic area, the near historical epidemic area, the rekindling epidemic area and the current epidemic area. The carrying rate of Yersinia pestis phages in the historical epidemic area and urban Rattus norvegicus is higher, which microecological significance is worth further discussion.