1. Department of Biology, University of New Brunswick, Bag Service # 45111, Fredericton, New Brunswick, E3B 6E1, Canada
2. Current address: James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, 14853, USA
3. Current address: 110 Drummond Street East, Perth, Ontario, K7H 1H1, Canada;
4. Current address: Large Animal Clinic, Veterinary Teaching Hospital, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5B4