Johne's disease (pronounced “yo-neez”) typically affects domestic ruminants such as cattle, sheep and goats. It is a progressive, incurable, wasting disease caused by bacterial infection of the intestines and other tissues. It is transmitted from an infected animal to herdmates primarily via the fecal-oral route.

Johne's disease is predominantly subclinical, meaning infected animals do not show outward signs of illness. This makes identifying infected cattle and managing the disease difficult. However, with diligence and patience, a herd's level of infection can be reduced. Left undetected and uncontrolled Johne's disease can prove costly to dairy or beef herds or small ruminant flocks.