1. a Department of Veterinary Pathology, Microbiology and Parasitology, Faculty of Veterinary Medicine , University of Nairobi , P.O. Box 29053, Nairobi , Kenya
2. b Administrations , The Open University of Tanzania , P.O. Box 23409, Dar Es Salaam , Tanzania
3. c Plant Breeding Station , Kenya Agricultural Research Institute , P.O. Njoro, Kenya
4. d Department of Veterinary Pathobiology, Faculty of Life Sciences , University of Copenhagen , Stigbøjlen 4, DK-1870 , Frederiksberg C , Denmark