1. Graduate Institute of Veterinary Public Health, National Chung Hsing University, Taichung 402, Taiwan
2. The Central Branch Office, Center for Disease Control, Taichung 408, Taiwan
3. Department of Veterinary Medicine, National Taiwan University, Taipei 106, Taiwan
4. Department of Microbiology and Immunology, School of Medicine, Taipei Medical University, Taipei 110, Taiwan
5. Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Children's Hospital, Taoyuan 333, Taiwan
6. Department of Applied Microbiology, National Chiayi University, Chiayi 600, Taiwan
7. Graduate Institute of Veterinary Pathology, National Chung Hsing University, Taichung 402, Taiwan
8. Department of Biological Science and Technology, School of Medicine, China Medical University, Taichung 404, Taiwan