How do deer/elk get infected?
Johne’s disease typically enters a herd when an infected, but healthy-looking, deer is purchased. This infected deer then sheds the organism onto the premises – perhaps onto pasture or into water shared by its new herdmates. Young animals are far more susceptible to infection than are adults: these calves swallow the organism along with grass, milk or water. (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.) Animals may even have been infected before they are born (in utero transmission) if the dam is infected. Thus the infection spreads, often without the owner’s being aware of it.
