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
6. University of Idaho, Caine Veterinary Teaching and Research Center, 1020 East Homedale Road, Caldwell, Idaho 83605-8098, USA