1. College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, 625014, China
2. Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University, B-9000 Ghent, Belgium;
3. Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium;
4. COVETOP, Consultancy in Veterinary and Toxicological Pathology, B-7850, Edingen, Belgium