1. Fitzpatrick Referrals Ltd.; Godalming Surrey GU7 2QQ UK
2. Veterinary Clinical Sciences, College of Veterinary Medicine; Washington State University; Pullman WA 99164 UK
3. School of Veterinary Medicine; University of Surrey; Guildford Surrey GU2 7XH UK
4. Department of Veterinary Medicine, Disease Dynamics Unit; University of Cambridge; Cambridge CB3 0ES UK