1. College of Medical; Veterinary and Life Sciences; University of Glasgow; Glasgow G12 8QQ UK
2. Faculty of Veterinary Medicine; Sokoine University of Agriculture; P. O. Box 3015, Chuo Kikuu Morogoro Tanzania
3. Centre for International Health; Dunedin School of Medicine; University of Otago; PO Box 56 Dunedin 9054 New Zealand