Affiliation: | (1) Institute for Animal Health, Compton, Newbury, Berkshire, RG20 7NN, UK;(2) Present address: Nuffield Department of Obstetrics and Gynaecology, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, UK;(3) Present address: Academic Unit of Pathology, School of Medicine and Biomedical Sciences, University of Sheffield, Beech Hill Rd, Sheffield, S10 2RX, UK |