This article written by Dr. Reynold Bergen, BCRC Science Director, originally appeared in the February 2019 issue of Canadian Cattlemen magazine and is reprinted on the BCRC Blog with permission of the publisher.
Johne’s disease is caused by a bacterium (Mycobacterium avium paratuberculosis, or MAP) that was discovered in 1895 by a heavily bearded, bespectacled bacteriologist from Dresden named Henrich Albert Johne. When a cow develops persistent, watery, smelly hosepipe diarrhea, and progressively loses weight and body condition even though her appetite is normal and she isn’t running a temperature, she may have Johne’s disease. But it can be hard to know for sure.
Young calves, which are more susceptible to infection than older animals, are often infected with MAP through colostrum, milk or manure. The animal will look perfectly normal, while silently shedding MAP in its own colostrum, milk or manure for a few years before full-blown signs of disease appear. As a result, Johne’s disease is often compared to an iceberg – by the time you see an obviously sick animal, there will be a much larger hidden population of MAP-infected cattle that haven’t become sick yet. Continue reading