1. Department of Small Animal Medicine and Surgery, The Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Herts, AL9 7TA. U.K.
2. Abbey Veterinary Services, 5 Hopkins Lane, Newton Abbot, Devon, TQ12 2EL. U.K.
3. Facultad de Veterinaria, Universidad Autonoma, E 08193, Barcelona, Spain
4. Faculty of Veterinary Medicine, Sokoine University of Agriculture, PO Box 1387, Morogoro, Tanzania