1. School of Biological Sciences, Cruickshank Building, St. Machar Drive, University of Aberdeen, Aberdeen AB24 3UU, United Kingdom
2. Section of Immunology and Infection, School of Medicine and Dentistry, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
3. Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3SY, United Kingdom
4. Gastrointestinal, Emerging and Zoonotic Infections, Health Protection Agency's Centre for Infections, 61 Colindale Avenue, London NW9 5EQ, United Kingdom