1. National Food Research Institute, Food Hygiene Team, 2-1-12 Kannondai, Tsukuba 305-8642, Japan
2. United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, Pennsylvania 19038
3. United States Department of Agriculture, Agricultural Research Service, National Animal Disease Center, 2300 Dayton Roa, Ames, Iowa 50010