1. a Department of Veterinary Anatomy , University of Nairobi , PO Box 30197, GPO, Nairobi, Kenya
2. b School of Physiology, Faculty of Medicine , University of the Witwatersrand , 7 York Road, Parktown, 2193, South Africa
3. c Faculty of Life Sciences, Department of Basic Animal and Veterinary Sciences , University of Copenhagen , Copenhagen, Denmark