Jarynowski, Andrzej, Interdisciplinary Research Institute, Oriona 15/8, 67-200 Głogów, Poland System Modeling Group, Institute of Veterinary Epidemiology and Biostatistics, Freie Universität Berlin, Königsweg 67, 14163 Berlin, Germany. Polish Hygienic Association, Lower Silesia District, Marii Curie-Skłodowskiej 73/77, 50-950 Wrocław, Poland, Germany