1. Department of Clinical Sciences of Companion Animals; Faculty of Veternary Medicine; University of Utrecht; PO Box 80154 3508 TD Utrecht The Netherlands
2. Department of Pathology; Faculty of Veternary Medicine; University of Utrecht; PO Box 80154 3508 TD Utrecht The Netherlands
3. Department of Herd Health and Reproduction; Faculty of Veternary Medicine; University of Utrecht; PO Box 80154 3508 TD Utrecht The Netherlands