1. Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 0W0
2. Present address: Animal Health Laboratory, Postal Bag Service #1, Airdrie, Alberta, Canada T4B 2C1
3. Health of Animals Laboratory, Agriculture Canada, 116 Veterinary Road, Saskatoon, Saskatchewan, Canada S7N 2R3
4. Present address: Animal Disease Research Institute, P.O. Box 640, Lethbridge, Alberta, Canada T1J 3Z4