Coccidiosis caused by Eimeria parasites is one of the most welfare-significant diseases in poultry, causing intestinal damage, bloody diarrhea, and high mortality.
Clinical coccidiosis causes intense suffering - intestinal hemorrhage, severe pain, and rapid deterioration. Even subclinical infection reduces growth, feed conversion, and immunity. The welfare significance is amplified by the scale of modern poultry production where millions of birds can be simultaneously affected. Prevention through vaccination is preferable to treating mass outbreaks.