1. Department of Microbiology and Immunology, Box 44, College of Medicine, State University of New York, 450 Clarkson Avenue, Brooklyn, NY 11203, USA
2. Animal Health Laboratory, Laboratory Service Division, University of Guelph, Guelph, Ontario, Canada NIH 6R8
3. Clinic for Pigs, Small Ruminants, Forensic Medicine and Ambulatory Service, School of Veterinary Medicine, D-30173 Hannover, Germany