Affiliation: | aInstitute for Animal Health, Compton, Berkshire, RG20 7BH, UK;bInternational Livestock Research Institute, P.O. Box 30705, Nairobi, Kenya;cDivision of Infection and Immunity, The Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK |