1. Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Center, U.S. Department of Agriculture, Athens, GA, USA
2. National Import Export Services, Veterinary Services, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Ames, IA, USA
3. Veterinary Services, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Riverdale, MD, USA