Introduction
Livestock contribute signifi cantly to the livelihoods of hundreds of millions of people worldwide. Many countries count receipts from trade in livestock and animal products as signifi cant contributions to their gross national product. Moreover, global demand for foods of animal origin is steadily growing and it is apparent that the livestock sector will continue to expand accordingly (FAO 2009b). In recent years, there have been notable increases in the occurrence of emerging and reemerging infectious diseases, many of them diseases of livestock with zoonotic potential.