1State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province 730046, P.R. China
2College of Animal Science and Technology, Jilin Agricultural University, Changchun, Jilin Province 130118, P.R. China. JFIF d d Ducky d qhttp://ns.adobe.com/xap/1.0/