The Species and Bioepidemiology of Alveolar Echinococcus in Xinbaerhu West County, Eastern Inner Mongolia

This communication reports the results of a survey on the bioepidemiology of alveolar echinococcus on grasslands of Xinbaerhu West County in Hulunbeier Pasture, Eastern Inner Mongolia ; and the results of experimental infections on laboratory white mice with adults of Echinococcus multilocularis (Leuckart, 1863) and Echinococcus sibiricensis Rausch and Schiller, 1954 collected from Vulpes corsac captured from West County. Three species of alveolar echinococcus were found from field voles, Microtus brandti in grasslands of Xinbaerhu West County. The three species of alveolar echinococcus were metacestodes of E. sibiricensis (89.4% in positive voles) and E. multilocularis (8.77%), and Alveolaris hulunbeierensis n. sp.(1.76%). These 3 alveolar echinococcus not only differed in the structure of alveolar cysts, but also in the development pattern. They showed different characteristics of separate species. In the present investigation, of the 647 Microtus brandti captured from three villages of Xinbaerhu West County, 67 (9.94%) were found to be infected with alveolar echinococcus. The infection rates were different in different villages, as follows: Eerdun Village 7.59% (35/461); Hulun Village 19.02% (31/163); Baogede Village 2.0% (1/50). Infection rates in Spring (April) 12.61%(15/119)~23.68%(9/38) and in Autumn (Sept.) 17.60% (22/125)~ 6.25 % (1/16) were higher than that in Summer (July) 5.85% (20/342)~0% (0/34). 36 Vulpes corsac , 6 Vulpes vulpes and 9 Canis lupus were captured from grasslands of Xinbaerhu West County and were examined. Adults of Echinococcus granulosus were found from 3 (33.3%) of 9 Canis lupus , Adults of Echinococcus sibiricensis were found from 2 (5.56%) of 36 Vulpes corsac, one of the 2 positive corsac foxes was mixed infected with the adults of Echinococcus multilocularis (2.76%). Under experimental condition, 203 white mice (Kunmin strain) were orally infected with both gravid proglottids of E. sibiricensis and E. multilocularis respectively and mixedly, which were collected from Vulpes corsac captured from Xinbaerhu West County. The alveolar cysts of E. sibiricensis were found from lungs of mice; many germinal cells masses existed in undiferrentiated embryonal cysts cavities of parasite, they metastasized off cysts into lung tissue of host to form brood capsules and protoscolice which manifested in 9 th month postinfection; host reaction strong. While the alveolar cysts of E. multilocularis developed in livers of white mice; germinal cells layer which attached on inner surface of cysts wall proliferated by budding pattern to form new vesicles; the protoscolice which grew from germinal cells layer manifested in 5 th and 6 th months postinfection; host reaction slight. The larval stages of the two species Echinococcus in experimentally infected white mice were similar to those in naturally infected Microtus brandti .