1. Department of Agriculture and Rural Affairs, Regional Veterinary Laboratory, P.O. Box 483, Bairnsdale, Victoria 3875, Australia
2. Department of Agriculture, Regional Veterinary Laboratory, Private Mail Bag, Armidale, New South Wales 2351, Australia
3. Mount Pleasant Laboratories, Dept. of Primary Industry, P.O. Box 46, Kings Meadows, Tasmania 7249, Australia
4. Department of Pathology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada N1G 2W1