1. Toyama Prefectural Seibu Livestock Hygiene Service Center, 343 Saburomaru, Tonami, Toyama 939-1308, Japan
2. Hokkaido Research Station, National Institute of Animal Health, National Agriculture and Food Research Organization, 4 Hitsujigaoka, Toyohira, Sapporo, Hokkaido 062-0045, Japan