What are the implications for dairy cattle?
Johne’s disease occurs worldwide. In the U.S. it is estimated that 7.8% of the beef herds and 22% of the dairy herds are infected with M. paratuberculosis. Johne’s disease typically enters a herd or flock of animals when an infected, but healthy-looking, animal is purchased. The infection then spreads to other animals, often without the owner’s being aware of it. Individual animals get infected by close contact with other infected animals that shed the bacterium in their manure. Most often, the infection is acquired by eating material contaminated with M. paratuberculosis when animals are very young. Young animals are far more susceptible to infection than are adults. Ingestion of the bacterium occurs when the newborn’s environment is contaminated with manure from an infected adult animal, or by drinking milk from an infected animal. The milk may become contaminated from the environment (manure-stained teats) or, in the advanced stages of the infection, the bacterium is shed directly i
