Experimental observation on the yellow mice(Citellus undulatus) infected with Yersinia pestis over the winter / 中国地方病学杂志

ABSTRACT

Objective To analysis and determine the possibility of the Citellus undulatus infected with Yersinia pestis surviving the winter in an experimental study, and to provide scientific experimental basis for the study on the mechanism of Yersinia pestis preservation. Method In 2006,09 to 2007,04 and 2007,09 to 2008,04 in Xinjiang Wusu-Gurtu natural foci of plague, under natural conditions, the over the winter process of Citellus undulatus carrying the plague bacteria was simulated, and 178 Citellus undulatus were infected with Yersinia pestis (1×107 Bacteria/mouse) using artificial injection method. One hundred seventy-eight Citellus undulatus infected with Yersinia pestis were kept into a construction of the black (1-5 ℃) basement (2 meters under the ground) in the plague focus. In doing so, these Citellus undulatuses almost simultaneously stepped into hibernation. After waking up from hibernation in following year in April, the survived mice carrying the plague bacteria were observed. Results Sixty-eight mice survived among the 178 infected with Yersinia pestis after 6 months of hibernation (through October to the following year in April), and the remaining 110 were all dead without pulling through the hibernation period. The survival rate was 38.2% (68/178). The organ culture of Yersinia pestis of the 110 dead mice(Citellus undnlatus) were tested, 67 were negative(-), 43 positive(+), with a positive rate of 39.1%(43/110). Among the rats with positive plague bacteria, the congestive pulmonary edema and the pathological changes of the hemorrhagic inflammation of the heart, liver, spleen, kidney and injection site could be seen clearly; the plague-free mice were not found to have any pathological changes. The survived 68 mice over the winter were autopsied and observed after being fed up for 20 days. No any pathological changes were found among these mice, and culturing of Yersinia pestis of the heart, liver, spleen, lungs and the tissue of injection site of these mice were all negative (-). Conclusions Citellus undulatus can carry Yersinia pestis during hibernation, but some fail to carry the bacteria through the entire process of hibernation persistently. Yersinia pestis was negative in the survived mice at the end of hibernation. The results showed that Citellus undulatus can not carry Yersinia pestis over the winter.