1. Plum Island Animal Disease Center, ARS, USDA, Greenport, New York, USA
2. Department of Pathobiology and Population Medicine, Mississippi State University, Mississippi State, Mississippi, USA
3. Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, Connecticut, USA
4. Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas, USA
5. Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee, USA