1. School of Veterinary Medicine, Department of Medicine and Epidemiology, University of California, Davis, California 95616, USA
2. Wildlife, Fish, and Conservation Biology, University of California, Davis, California 95616, USA
3. Arizona Department of Fish and Game, 2221 W. Greenway Road, Phoenix, Arizona 85023, USA
4. School of Veterinary Medicine, Department of Pathology, Microbiology, and Immunology, University of California, Davis, California 95616, USA