1. Laboratory of Molecular Pathobiology, Department of Pharmacology and Pathobiology, The Royal Veterinary and Agricultural University, DK-1870 Frederiksberg C, Denmark Lindholm, DK-4771 Kalvehave, Denmark
2. Danish Veterinary Laboratory, DK-1790 Copenhagen V, Denmark Lindholm, DK-4771 Kalvehave, Denmark
3. Danish Veterinary Institute for Virus Research, Lindholm, DK-4771 Kalvehave, Denmark