1. a Gribbles Veterinary Pathology, Invermay , PO Box 371, Mosgiel E-mail:
2. b School of Veterinary and Biomedical Sciences, Division of Health Sciences , Murdoch University , Perth, Western Australia
3. c ESR Ltd, Kenepuru Science Centre , PO Box 50348, Porirua, New Zealand
4. d Schering-Plough Animal Heath Ltd , Private Bag 908, Upper Hutt, New Zealand
5. e Healthcare Otago , PO Box 5144, Dunedin, New Zealand
6. f Institute of Veterinary, Animal and Biomedical Sciences , Massey University , Private Bag 11222, Palmerston North, New Zealand