1. Department of Veterinary Science, University of Wisconsin, 1655 Linden Drive, Madison, Wisconsin 53706, USA
2. Present address: National Wildlife Health Research Center, 6006 Schroeder Road, Madison, Wisconsin 53711, USA
3. School of Veterinary Medicine, University of Wisconsin, 2015 Linden Drive, Madison, Wisconsin 53706, USA
4. (Deceased) Former address: Bureau of Wildlife Management, Department of Natural Resources, Madison, Wisconsin 53707, USA