1. Federation of Danish Pig Producers and Slaughterhouses; Veterinary Division; 11 Vinkelvej DK-8620 Kjellerup Denmark
2. Federation of Danish Pig Producers and Slaughterhouses; Veterinary Division, Axelborg; 3 Axeltorv DK-1609 Copenhagen V Denmark
3. Danish Veterinary Laboratory; 27 Bulowsvej DK-1790 Denmark