The Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, South Parks Road Oxford OX1 3PS, UK. Vitali.Proutski@zoology.oxford.ac.uk|The Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, South Parks Road Oxford OX1 3PS, UK. Vitali.Proutski@zoology.oxford.ac.uk