1. U.S. Geological Service, National Wildlife Health Center, 6006 Schroeder Road, Madison, Wisconsin 53711, USA
2. Current Address: Wyoming Department of Health, Wyoming State Vet Lab, 1174 Snowy Range Road, Laramie, Wyoming 82070, USA
3. U. S. Department of Agriculture, National Wildlife Research Center, 4101 LaPorte Avenue, Fort Collins, Colorado 80521, USA