1. Introduction through contaminated feed or water sources 2. Introduction through infected animals brought into the herd or flock 3. Spread through direct contact between animals 4. Spread through contact with contaminated equipment or facilities 5. Spread through airborne transmission 6. Spread through vectors such as insects or rodents 7. Spread through contaminated bedding or manure 8. Spread through contaminated clothing or footwear of farm workers 9. Spread through contaminated vehicles or machinery 10. Spread through contact with wildlife carrying the disease.