The correlation of meteorological factors with the numbers of marmots and parasitic fleas in the marmot plague foci in Subei County and Sunan County of Gansu Province / 中华地方病学杂志

ABSTRACT

Objective To investigate the correlation of meteorological factors with the numbers of marmots and parasitic fleas in the plague foci of Himalayan marmot in Subei County and Sunan County of Gansu Province.Methods The surveillance data (from Gansu Provincial Center for Disease Control and Prevention) of natural plague foci of Subei,Sunan of Himalayan marmot from 1982 to 2016 and the meteorological factors data (from China Meteorological Data Sharing Service Network) such as annual average temperature,rainfall and relative humidity during the same period were collected.The correlation between marmot density,body flea index and meteorological factors were analyzed by SAS 9.3 software.Based on the meteorological data as an independent variable in current year and previous 1,2,and 3 years (relative to previous 1,2,and 3 years as the reference),the marmot density as the dependent variable,the time series semiparametric generalized additive model (GAM) was established to quantitatively study the nonlinear effect of meteorological factors on the marmot density by R2.3.2 software.Results From 1982 to 2016,the marmot density in Subei County of Gansu Province was 0.29-6.63 per hectare,and the body flea index range was 0.04-4.56;the marmot density in Sunan County of Gansu Province was 1.22-7.92 per hectare,and the body flea index range was 0.06-0.42.In Subei County,the marmot density was correlated with the previous 1 year rainfall and relative humidity,respectively (r =0.43,0.36,P＜ 0.05),and negatively correlated with the average temperature of the year and the previous 1,3 years (r =-0.58,-0.55,-0.41,P ＜ 0.05).In Sunan County,the marmot density was correlated with the relative humidity of the year and the previous 1 year rainfall and relative humidity,respectively (r =0.36,0.57,0.43,P ＜ 0.05).In Subei County,the body flea index was negatively correlated with the average temperature of the year and the previous 1,2,3 years,respectively (r =-0.57,-0.43,-0.31,-0.37,P ＜ 0.05).In Sunan County,there was a negative correlation between the body flea index and the average temperature of the year and the previous 1,2,3 years (r =-0.71,-0.46,-0.38,-0.40,P ＜ 0.05).After controlling other influencing factors,the results of the GAM showed that for every 1 mm increase in rainfall of the year in Subei County,the marmot density increased 0.93％;for every 1％ increase in relative humidity of the previous 3 year in Subei County,the marmot density increased 25.34％;for every 1 mm increase in rainfall of the previous 3 year in Sunan County,the marmot density increased 1.69％.Conclusions The numbers of marmots in the plague foci of Himalayan marmot in Subei County and Sunan County of Gansu Province are closely related to rainfall and relative humidity,and the influence has different hysteresis effects.Surface temperature is a important factor affecting the population of parasitic fleas.