1. Veterinary Medicine Department University of Bari Aldo Moro Valenzano Bari 70010 Italy
2. Department of Microbiology and Immunology National Research Centre Cairo Egypt
3. Department of Veterinary Medicine and Animal Productions University of Napoli Federico II Napoli Italy
4. Istituto Zooprofilattico Sperimentale del Mezzogiorno Portici Italy
5. Department of Population Health and Reproduction, School of Veterinary Medicine University of California Davis CA 95616 USA