1. Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N OWO, Canada
2. Present address: Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA
3. Department of Renewable Resources, Government of the Northwest Territories, Inuvik, Northwest Territories XOE OTO, Canada
4. Department of Renewable Resources, Government of the Northwest Territories, Coppermine, Northwest Territories XOE OEO, Canada