1 MRC-University of Glasgow Centre for Virus Research, Henry Wellcome Building, Garscube Estate, Bearsden Road, Glasgow G61 1QH.
2 Institute of Biodiversity, Animal Health and Comparative Medicine, Graham Kerr Building, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow G12 8QQ.
3 Veterinary Diagnostic Services, School of Veterinary Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Bearsden Road, Glasgow G61 1QH.