1. College of Veterinary Medicine and Shanxi Agricultural University, Taigu, China.
2. Laboratory Animal Center, Shanxi Agricultural University, Taigu, China.
3. Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA.
4. Department of Surgery, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.