1. Unit of Medical Biology and Environment, Institut Pasteur, Dakar, Senegal.
2. Unit of Epidemiology, Institut Pasteur, Dakar, Senegal.
3. Department of Breeding, Ministry of Breeding, Dakar, Senegal.
4. Inter-States School of Veterinary Sciences and Medicine, Dakar, Senegal.
5. Research and Technological Exchange Group, Dakar, Senegal.
6. National Reference Centre for Listeria, Institut Pasteur, Paris, France.