1. National Reference Centre for Transmissible Spongiform Encephalopathies, Animal Pathology Department, Veterinary Faculty, C/Miguel Servet 177, 50013 Zaragoza, Spain
2. Biochemical Genetics and Blood Groups Laboratory, University of Zaragoza, C/Miguel Servet 177, 50013 Zaragoza, Spain
3. Institute for Animal Health, Neuropathogenesis Unit, West Mains Road, Edinburgh EH9 3JF, UK