1. Petvett Ekeberg Small Animal Clinic, Ekebergveien 177, 1177 Oslo, Norway
2. Sørlandets Animal Clinic, branch office Farsund, Gamle Mosvoldvei 1, 4550 Farsund, Norway
3. Department of Food Safety and Infection Biology
4. Centre for Epidemiology and Biostatistics
5. Department of Companion Animal Clinical Sciences, Norwegian School of Veterinary Science, Postboks 8146 Dep, 0033 Oslo, Norway