1. Department of Internal Medicine and Infectious Disease, College of Veterinary Medicine, Seoul National University, San 56-1, Sinlim-dong, Seoul, 151-742, Republic of Korea
2. Department of Internal Medicine, College of Veterinary Medicine, Kangwon National University, 192-1 Hyoja-2 dong, Chunchon city, Kangwon-do, 200-701 Republic of Korea