1. Section of Epidemiology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
2. Department of Medicine, Swiss Tropical and Public Health Institute and University of Basel, Basel, Switzerland
3. School of Veterinary Science, Massey University, Private Bag 11222, Palmerston North, 4412, New Zealand
4. Preventive Veterinary Medicine Institute, Austral University of Chile, Valdivia, Chile