1. College of Public Health, George Mason University, Fairfax, VA 22030, USA
2. College of Veterinary Medicine, Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, IA 50011, USA
3. Department of Veterinary Population Medicine (VPM), College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA
4. Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA