Johne’s disease is a centuries-old ailment in dairy cattle that
infects about 21 percent of the U.S. herd and causes losses of
about $200 million per year. It is a chronic enteritis that causes
diarrhea, weight loss, decreased milk production, and death. T h e
major concern is the ease with which it spreads throughout a
herd via contact with feces or milk from even one infected animal
to calves.