What are the symptoms of Johnes disease and what causes them?
There really are only two clinical signs of Johne’s disease: rapid weight loss and diarrhea. In deer or elk, diarrhea may be less common than in cattle. The infection occurs in calves in the first months of life, but signs of disease usually do not appear until the animals are adults. Despite continuing to eat well, adult deer become emaciated and weak. Since the signs of Johne’s disease are similar to those for several other diseases, laboratory tests are needed to confirm a diagnosis. If a case of Johne’s disease occurs, it is very likely that other infected deer or elk (who may still appear healthy) are in the herd. No one yet understands what causes a clinically normal animal that has been infected by MAP for months or years to suddenly become sick from the infection. We do know that at some point the MAP that have been lying quiet within cells of the last section of the small intestine (called the ileum) start to replicate and take over more and more of the tissue. The animal’s im
