1. Institute of Behavioural Physiology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany
2. Division of Infection and Immunity, University College London, Cruciform Building, Gower Street, London WC1 6BT, UK
3. Experimental Pediatrics, University Hospital, Otto-von-Guericke University Magdeburg, Leipziger Straße 44, 39120 Magdeburg, Germany