1 National Reference Centre for Infectious Bovine Rhinotracheitis (IBR), Istituto Zooprofilattico Sperimentale Umbria-Marche, Via Gaetano Salvemini 1, 06126 Perugia, Italy.
2 Division of Clinical Neuroscience, Section of Clinical Neurology, University of Nottingham, Nottingham NG7 2UH, UK.
3 Department of Neurology, Nottingham University Hospitals NHS Trust, Nottingham NG7 2UH, UK.