Johne's disease (paratuberculosis) is a chronic, progressive intestinal disease of cattle caused by Mycobacterium avium subspecies paratuberculosis, causing wasting and death after years of subclinical infection.
Johne's disease causes a prolonged welfare deterioration. The clinical phase — profuse diarrhea, protein loss causing bottle jaw edema, and progressive emaciation — represents months of suffering before animals deteriorate to the point where culling is considered. The insidious nature of the disease means that moderately affected animals continue in reduced welfare for extended periods before clinical signs are recognized. Control programs that reduce calf exposure — through hygienic calving environments and colostrum management — represent the most effective welfare intervention. Timely identification of clinically affected animals and prompt culling rather than prolonged management is the most direct welfare improvement available once disease is established.