1. Department of Epidemiology and Preventive Medicine, School of Veterinary Medicine, University of California, Davis, California 95616, USA
2. United States Department of Agriculture, National Animal Disease Center, Agriculture Research Service, Central Plains Area, P.O. Box 70, Ames, Iowa 50010, USA
3. California Veterinary Diagnostic Laboratory System, P.O. Box 1770, University of California, Davis, California 95616, USA
4. The Resources Agency, California State Department of Parks and Recreation, Anza-Borrego Desert State Park, P.O. Box 299, Borrego Springs, California 92004, USA
5. The Resources Agency, California State Department of Fish and Game, Wildlife Investigations Laboratory, 1701 Nimbus Road Suite D, Rancho Cordova, California 95819, USA