How do animals get Johnes disease?
Johne’s disease typically enters a herd of animals when an infected, but healthy-looking, animal is bought. The infection then spreads to other animals without the owner’s knowledge. Eventually, often after several years, the owner recognizes signs of the disease in a number of animals. Individual animals get infected most often when they are calves less than 6 months old. They get infected by consuming milk, water, or feed contaminated with M. paratuberculosis. Young calves 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 animal, or by drinking milk from an infected animal. Feeding waste milk to calves is most responsible for spread of Johne’s disease in dairy herds. After infection, many months or years go by until the infected animals shows signs of Johne’s disease.
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. Eventually, perhaps after several years, the owner recognizes signs of the disease in a number of animals. 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 into the milk. This has been shown to occur in da
