Correlation between prevalence of marmot plague and meteorological factors in the natural plague foci of Subei County, Gansu Province

Objective To analyze the relationship between meteorological variables and the prevalence of marmot plague in the Himalayan marmot foci of Subei County, Gansu Province. Methods The surveillance data (from Gansu Provincial Center for Disease Control and Prevention) on human plague, the meteorological factors (average rainfall, temperature, relative humidity) data (from China Meteorological Data Sharing Service Network) of the current and preceding (relative to current year as a reference) first, second and third years and meteorological factors data of the current and preceding first, second and third months in Subei of Himalayan marmot foci from 1973 to 2014 were collected. The association of positive rate of plague bacteriological detection and meteorological factors was evaluated by using SAS 9.3 software. The influence of meteorological factors on the epidemic of marmot plague was analyzed by the logistic regression analysis. Results From 1973 to 2014, 6 human plague cases with 5 dead cases occurred in Subei County. The positive rate of plague bacteriological detection was positively correlated with the average relative humidity of current year and the average temperature of preceding first year (r=0.366, 0.385, P < 0.05), and it was negatively correlated with the average relative humidity of preceding third year (r=- 0.304, P < 0.05); the positive rate of plague bacteriological detection was positively correlated with the average rainfall of preceding first month (r=0.212, P < 0.05), and it was negatively correlated with the average relative humidity of preceding second and third months (r=- 0.196,-0.201, P < 0.05). The risk factor of animal plague epidemic in marmot foci in Subei County was average temperature of current month [odds ratio (OR)=1.304, 95% confidence intervals (CI): 1.195-1.422], and the protective factor was average relative humidity of preceding third month (OR=0.960, 95%CI: 0.932-0.988). Conclusions The prevalence of marmot plague is closely associated with meteorological factors in the natural plague foci of Subei County of Gansu Province. The temperature not only plays a role in promoting the prevalence of plague, but also has a lagging effect. Therefore, the meteorological factors can be considered as a reference of the plague prevalence in Himalayan marmot plague foci. Key words: Marmota; Yersinia pestis; Meteorology; Association