Päivi Rajala-Schultz1, Karin Persson Waller2, Tariq Halasa3, Ane Nødtvedt4. 1. University of Helsinki, Paroninkuja 20, 00014, Finland. 2. National Veterinary Institute, Uppsala SE-751 89, Sweden and Swedish University of Agricultural Sciences, Uppsala SE-750 07, Sweden. 3. University of Copenhagen, Grønnegårdsvej 15, 1870 Frederiksberg C, Denmark. 4. Norwegian University of Life Sciences, Bygning 11, 303, Adamstuen, Norway.