1. Animal Diseases Research Institute, Agriculture Canada, PO Box 11300, Station H, Nepean, ON K2H 8P9, Canada
2. Institute for Animal Health, Pirbright Laboratory, Ash Road, Pirbright, Woking GU24 ONF, England, UK
3. Australian Animal Health Laboratory, PO Bag 24, Geelong, Victoria 3220, Australia
4. USDA, National Veterinary Services Laboratories, PO Box 844, Ames, IA 50010