1. Department of Animal Medicine and Surgery; School of Veterinary Medicine, Universidad Complutense de Madrid; Avda. Puerta de Hierro s/n 28040-Madrid Spain
2. Centre for Equine Studies; Animal Health Trust; Kentford Newmarket Suffolk CB8 7UU UK
3. Centre for Small Animal Studies; Animal Health Trust; Kentford Newmarket Suffolk CB8 7UU UK
4. Department of Clinical Sciences; Cummings School of Veterinary Medicine, Tufts University; 200 Westboro Road North Grafton MA 01536 USA