1. Ontario Ministry of Agriculture and Food, Veterinary Laboratory Services, Box 3612, Guelph, ON N1H 6R8, Canada
2. Ontario Veterinary College, Department of Veterinary Microbiology and Immunology, University of Guelph, Guelph, ON N1G 2W1, Canada
3. Ontario Ministry of Agriculture and Food, Veterinary Laboratory Services, Mail Bag 2005, Kemptville, ON KOG 1J0, Canada