1. Unit of Medical Statistics and Molecular Epidemiology, Università Campus Bio-Medico di Roma, Rome, Italy
2. Department of Biomedical Sciences, University of Sassari, Sassari, Italy
3. Department of Veterinary Medicine, University of Sassari, Sassari, Italy
4. Department of Public Health and Infectious Diseases, University Hospital Policlinico Umberto I, Sapienza University of Rome, Rome, Italy