| Shiqu county of Sichuan province is one of the high epidemic areas of alveolar echinococcosis in China.The prevalence rate of alveolar echinococcosis among local residents reaches up to 6.2%.During October to the next May,the pastoralists live in the settlements that have an average altitude of 4100 meters,that is,winter pasture.While during May to September,they nomadize in the zone of migration 4200 meters to 4800 meters above the sea level,that is,summer pasture.Rodentia and Lagomorpha animals are the intermediate hosts and dogs are the most significant definitive hosts of Echinococcus multilocularis in Shiqu.Therefore,distribution and infection of Alveolar echinococcus in Rodentia and Lagomorpha animals may facilitate to estimate the infection rate of dogs in winter and summer pastures respectively.In this study,the distribution and infection of intermediate hosts of alveolar echinococcosis were investigated,in order to provide references for making suitable strategy for Alveolar echinococcosis control and prevention.In the winter and summer pastures,47 and 50 survey spots were selected and each survey spot is 100 square meters in the area.The cave densities of the predominant species of Rodentia and Lagomorpha animals-Ochotona curzoniae and Microtus fuscus were investigated,and histopathologic method was used to examine the infection rates of alveolar echinococcus in the captured Ochotona curzoniae and Microtus fuscus.The results showed that Ochotona curzoniae and Microtus fuscus distributed both in winter and summer pastures,and their cave densities were 4.81 and 30.1 per 100 square meter in winter and summer pastures respectively,and their according cave density in summer pasture was higher than in winter pasture(F=36.65,P＜0.0001),and the infection rates of alveolar echinococcus were 5.75%and 9.04%respectively.The above results showed that Ochotona curzoniae and Microtus fuscus were the main intermediate hosts of Echinococcus multilocularis.According to the densities of Ochotona curzoniae,Microtus fuscus and their cave densities in 12 and 14 survey points investigated respectively,a regression equation was fitted with.(Ochotona curzoniae,P＜0.0001,R~2=0.8705,Microtus fuscus,P＜0.0001, R~2=0.9736).As a result,their cave densities could reflect the according animal densities. The distribution of both kind of animals in winter and summer pastures was deduced from the regression equation,which indicate that the average density of Ochotona curzoniae and Microtus fuscus were 46 peace/hectare,I peace/hectare respectively in winter pastures and 116 peace/hectare,137 peace/hectare respectively in summer pastures.The cave densities of Ochotona curzoniae and Microtus fuscus in different landscapes-grassland,semi-wasteland and wasteland were 5.38,23.08 and 26.34 per 100 square meter respectively.The ANOVA results showed that the cave densities of Ochotona curzoniae and Micrtus fuscus in wasteland and semi-wasteland were higher in compare with that in grassland(F=7.73,P＜0.001),which indicated that their main scopes of activity were wasteland and semi-wasteland.The spatial distribution of their main scopes of activity was showed according to the features of the satellite images among different landscapes-grassland,semi-wasteland and wasteland.The percentage of wasteland and semi-wasteland constituted 35.507%of the total survey areas,which showed that the two kinds of animals distributed widely.The infection rate of Ochotona curzoniae and Microtus fuscus in winter and summer pastures were 11.66%and 3.4%respectively.It was indicated that there were transmission of Alveolar hydatid dasease both in winter and summer pastures.This study revealed that Ochotona curzoniae and Microtus fuscus were important intermediate hosts of Echinococcus multilocularis,and they distributed widely.Both winter and summer pastures were focuses of natural infection of alveolar hydatid disease. It is necessary to persist in expelling worms in dogs every month during nomadism.
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