1. United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center, 4101 LaPorte Avenue, Fort Collins, Colorado 80521-2154, USA and Colorado State University, Fort Collins, Colorado 80523, USA
2. Current address: Southeastern Cooperative Wildlife Disease Study, Wildlife Health Building, College of Veterinary Medicine, The University of Georgia, Athens, Georgia 30602-4393, USA
3. Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, Colorado 80523, USA
4. Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado 80523, USA