1. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 5011, USA.
2. 352 Food Science Complex, University of Nebraska, Lincoln, NE 68583, USA.
3. Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI 53715, USA.
4. Merck Animal Health, DeSoto, KS 66018, USA.