1. School of Life Sciences, Shandong University, Jinan, China.
2. Shandong Provincial Center for Animal Disease Control and Prevention, Jinan, China.
3. Weihai City Center for Animal Disease Control and Prevention, Weihai, China.
4. School of Public Health, Shandong University, Jinan, China.
5. Wuhan University School of Health Sciences, Wuhan, China.
6. Department of Pathology, University of Texas Medical Branch, Galveston, Texas.