Effects of meteorological factors on prevalence of animal plague in the natural plague foci of Spermophilus alaschanicus of Gansu Province / 中华地方病学杂志

ABSTRACT

Objective To explore the effects of meteorological factors on population densities of the host and the prevalence of animal plague in the natural plague foci of Spermophilus alaschanicus.Methods The surveillance data of seroprevalence rate in natural plague foci of Spermophilus alaschanicus of Gansu Province in current year,one previous year (relative to current year as a reference),as well as two and three previous years’ meteorological data such as average annual rainfall,temperature,relative humidity were collected from 1962 to 2014.SAS 9.3 software was used for correlation and regression analysis of the influencing meteorological factors on the density of Spermophilus alaschanicus and prevalence of animal plague;generalized additive model (GAM) was used for quantitative study of meteorological factors on density of Spermophilus alaschanicus;logistic regression analysis was used to study the effect of meteorological factors on prevalence of Spermophilus alaschanicus plague.Results Serum positive rate of Spermophilus alaschanicus was positively correlated with average annual rainfall of current and previous one year,and with relative humidity of current year (r =0.279,0.341,0.654,P ＜ 0.05);serum positive rate was negatively correlated with average annual temperature of current and preceding first,second and third years (r =-0.360,-0.339,-0.273,-0.323,P ＜ 0.05).The average annual rainfall of preceding second and third years was significantly associated with the densities of Spermophilus alaschanicus by GAM parameter estimation (t =2.88,2.42,P ＜ 0.05).The average annual rainfall of preceding second and third years was significantly associated with the densities of Spermophilus alaschanicus by GAM nonparameter estimation (x2=31.580,13.428,P ＜ 0.05),but the effect was nonlinear.Multivariate logistic regression analysis showed that average annual rainfall of preceding first year [odds ratio (OR) =2.475,95％ confidence interval (C/)1.175-5.213] was risk factor for the prevalence of the animal plague in the natural plague foci of Spermophilus alaschanicus.Conclusions Rainfall is risk factor for the prevalence of the animal plague in the natural plague foci of Spermophilus alaschanicus.There is a lag effect of rainfall on the numbers of hosts and the prevalence of Spermophilus alaschanicue plague.When the rainfall in the region (not continuously) reaches a certain amount,it will provide favorable conditions for the spread of Yersinia pestis.