1. Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Denmark, Department of Natural Sciences, Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871, Denmark, and Department of Veterinary Diagnostics and Research, Danish Institute for Food and Veterinary Research (DFVF), Bülowsvej 27, DK-1790, Denmark