1. School of Veterinary Studies, Murdoch University, Murdoch, Western Australia 6150, Australia
2. Current address and address for correspondence: Animal Health Laboratory, Department of Agriculture, Baron Hay Court, South Perth, Western Australia 6151 Australia
3. Atlantis Marine Park, Two Rocks, Western Australia 6052, Australia
4. Current address: Werribee Zoological Park, P.O. Box 274, Werribee, Victoria 3030 Australia