How do goats get infected?
Johne’s disease typically enters a herd when an infected, but healthy-looking, goat is purchased. This infected goat 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 kids swallow the organism along with grass or water. Perhaps they are bottle-fed with MAP-contaminated milk collected from the infected but healthy-appearing new arrival. (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 doe is infected. Thus the infection spreads, often without the owner’s being aware of it.
