1. Food and Drug Administration, Center for Veterinary Medicine, Office of Research, Laurel, Maryland.
2. University of Wisconsin at Madison, Madison, Wisconsin.
3. Michigan State University, College of Veterinary Medicine, East Lansing, Michigan.
4. North Carolina State University, College of Agriculture and Life Science, Raleigh, North Carolina.
5. Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, Ohio.