1. Colorado Division of Wildlife, Wildlife Research Center, 317 West Prospect Road, Fort Collins, Colorado 80526-2097, USA
2. Fort Dodge Laboratories, 800 Fifth Street Northwest, Fort Dodge, Iowa 50501, USA
3. Present address: Rhone Merieux, Incorporated, 115 Transtech Drive, Athens, Georgia 30601, USA
4. Ayerst Veterinary Laboratories, 131 Malcolm Road, Guelph, Ontario N1K 1A8, Canada
5. Present address: Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada