1. 1Danish Institute for Fisheries Research, Department of Seafood Research, Søltofts Plads, c/o Technical University of Denmark, Building 221, DK-2800 Kgs. Lyngby, Denmark
2. 2Statens Serum Institut, DK-2300 Copenhagen, Denmark
3. 3Department of Veterinary Microbiology, The Royal Veterinary and Agricultural University, DK-1870 Frederiksberg, Denmark
4. 4Danish Veterinary Institute, DK-1790 Copenhagen V, Denmark