1. Department of Veterinary Sciences, University of Wyoming, 1190 Jackson, Laramie, Wyoming 82070, USA
2. Wyoming Game and Fish Department, Box 3312 University Station, Laramie, Wyoming 82071, USA
3. James A. Baker Institute for Animal Health, Department of Microbiology, New York State College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
4. Wyoming Game and Fish Department, 260 Buena Vista, Lander, Wyoming 82520, USA