1. Department of Microbiology, Immunology and Pathology, Colorado State University, 1644 Campus Delivery, Fort Collins, Colorado 80523, USA
2. Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, 3156 Rampart Road, Fort Collins, Colorado 80521, USA
3. National Wildlife Research Center, Wildlife Services, Animal and Plant Health Inspection Services, US Department of Agriculture, 4101 La Porte Avenue, Fort Collins, Colorado 80521, USA
4. Department of Biomedical Sciences, Colorado State University, 3107 Rampart Road, Fort Collins, Colorado 80521, USA