1. Faculty of Medicine, University of Khartoum, Khartoum, Sudan;
2. Brucella Department, Veterinary Research Institute, Khartoum, Sudan;
3. Institute of Tropical Medicine, Antwerp, Belgium;
4. Department of Microbiology and Immunology, KU Leuven, University of Leuven, Leuven, Belgium;
5. Division of Tropical and Humanitarian Medicine, Geneva University Hospitals, Geneva, Switzerland