1. Canadian Food Inspection Agency, Lethbridge, Alberta T1H 6P7, Canada;
2. Center for Food Security and Public Health, College of Veterinary Medicine, Iowa State University, Ames, Iowa 50011;
3. Food Animal Health Research Program, Ohio Agricultural Research and Development Center, College of Food, Agriculture and Environmental Sciences, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, Ohio 44691;