Establishment of animal model for Echinococcus inoculation infection in Microtus fuscus in Qinghai-Tibet Plateau

Objective To analyze whether Microtus fuscus in Qinghai-Tibet Plateau can be used as an animal model for Echinococcus infection.Methods Sixty wild voles (Microtus fuscus) were equally divided into groups A, B, and C to undergo Echinococcus inoculation through subcutaneous injection, direct transhepatic approach, and percutaneous transhepatic approach, respectively.Three months later, the infection rate and mortality rate were determined.After the model animals were sacrificed, HE staining was performed for the infiltration zone of lesion (2-3 mm near the lesion) , the area adjacent to the lesion and 50% of the lesion, the center of lesion (non-liquefied area) , the liquefied area of lesion, the margin of lesion (not including the normal tissue) , and 70% of the lesion, and the pathological structures of hydatid lesions were observed under a microscope.Protoscoleces were extracted from the lesions for in vitro culture.The chi-square test was used for comparison of categorical data.Results The success rate of Echinococcus infection in groups A, B, and C were 60%, 80%, and70%, respectively, with no significant difference between the three groups (χ2= 4.138, P = 0.126) .The mortality rates of groups A, B, and C were 5%, 20%, and 15%, respectively, with no significant difference between the three groups (χ2= 5.201, P = 0.107) .HE staining showed that the red-stained vesicles had thin, discontinuous cuticular layers, with massive inflammatory cell infiltration around the vesicles; no protoscoleces were observed in all sections.After in vitro culture and staining of the lesion tissue, a large number of live protoscoleces were observed, unstained and with motility.Conclusion This study confirms that Microtus fuscus, an endemic species in Qinghai-Tibet Plateau, can be used as an animal model for Echinococcus infection.Subcutaneous injection is an appropriate method for Echinococcus inoculation.