1. Section of Arctic Veterinary Medicine, Department of Food Safety and Infection Biology, The Norwegian School of Veterinary Science, Stakkevollveien 23, NO 9010 Tromsø
2. Section of Microbiology, Immunology, and Parasitology, Department of Food Safety and Infection Biology, The Norwegian School of Veterinary Science, P.O. Box 8146, NO 0033 Oslo, Norway