[1] Sichuan Agr Univ, Coll Vet Med, Chengdu 611130, Peoples R China
[2] Sichuan Agr Univ, Inst Prevent Vet Med, Chengdu 611130, Peoples R China
[3] Shandong Agr Univ, Dept Vet Med, Tai An 271018, Shandong, Peoples R China
[4] Univ Perugia, Dept Vet Med, I-06126 Perugia, Italy
[5] Univ Sassari, Dept Vet Med, I-07100 Sassari, Italy
[6] Chinese Acad Agr Sci, Lanzhou Vet Res Inst, Lanzhou 730046, Peoples R China