[1] Shandong Agr Univ, Coll Vet Med, Tai An 271018, Shandong, Peoples R China
[2] Texas A&M Univ, Coll Vet Med & Biomed Sci, Dept Vet Pathobiol, College Stn, TX 77843 USA
[3] Chinese Acad Agr Sci, Biotechnol Res Inst, Beijing 100081, Peoples R China
[4] China Inst Vet Drug Control, Beijing 100081, Peoples R China