[1] Univ Copenhagen, Dept Vet & Anim Sci, Copenhagen, Denmark
[2] Aarhus Univ, Dept Anim Sci, Blichers Alle 20, DK-8830 Tjele, Denmark
[3] Natl Vet Inst, Dept Dis Control & Epidemiol, S-75189 Uppsala 7, Sweden
[4] Danish Vet Assoc, Peter Bangs Vej 30, DK-2000 Frederiksberg, Denmark
[5] VIER PFOTEN, Stiftung Tierschutz, Linke Wienzeile 236, A-1150 Vienna, Austria