However, they do not produce as much milk and may be more susceptible to other problems, such as infertility. Johne s Disease is spread by feed and water that is contaminated with the bacteria. Infected animals shed the bacteria in their manure. Feed troughs, water tanks, maternity pens and other group pens can become contaminated by an infected animal or by equipment that has been used to feed animals or spread manure. Newborn animals and young animals can ingest the bacteria on manure covered teats, or in colostum or milk from infected cows.
Infected cows can infect their unborn calves.
Newborn animals are most susceptible to infection. All breeds of dairy and beef cattle can be infected. Infection rates in cattle herds may be 7 percent or higher. Several years ago, a survey indicated that 12 to 15 percent of cattle herds in North Carolina may have at least one animal with Johne s Disease. For every animal showing clinical signs, there may be 10 to 15 or more animals of different ages that are infected.