Johne's disease (pronounced "yo-knees") is a contagious, chronic and usually fatal infection that affects primarily the small intestine of ruminants. All ruminants are susceptible to Johne's disease. Johne's disease is caused by Mycobacterium avium subspecies paratuberculosis, a hardy bacteria related to the agents of leprosy and tuberculosis. The disease is worldwide in distribution.
A national study of US dairies, Dairy NAHMS 96, found that approximately 22 percent of US dairy farms have at least 10% of the herd infected with Johne's disease. The study determined that infected herds experience an average loss of $40 per cow in herds with a low Johne's disease clinical cull rate while herds with a high Johne's disease clinical cull rate lost on average of $227. This loss was due to reduced milk production, early culling, and poor conditioning at culling. The cost of Johne's disease in beef herds still need to be determined.
Signs of Johne's disease include weight loss and diarrhea with a normal appetite. Several weeks after the onset of diarrhea, a soft swelling may occur under the jaw (bottle jaw). Bottle jaw or intermandibular edema is due to protein loss from the bloodstream into the digestive tract. Animals at this stage of the disease will not live very long, perhaps a few weeks at most.
Signs are rarely evident in cattle until two or more years after the initial infection, which usually occurs shortly after birth. Animals are most susceptible to the infection in the first year of life. Newborns most often become infected by swallowing small amounts of infected manure from the birthing environment or udder of the mother. In addition, newborns may become infected while in the uterus or by swallowing bacteria passed in milk and colostrum. Animals exposed at an older age, or exposed to a very small dose of bacteria at a young age, are not likely to develop clinical disease until they are much older than two years.
Farm specific plans can be implemented to reduce economic losses and cleanup Johne's disease from the farm. For more information on Johne's disease, diagnosis, prevention, and control, contact your herd veterinarian or your State's extension office. Work with your veterinarian to develop a strategic plan for Johne's prevention and control for your farm.
Some basic prevention strategies are:
Consult with your veterinarian about which Johne's test is best for your situation and use an APHIS approved diagnostic laboratory.
Click here for a list of laboratories which have passed the Johne's serology and/or organism detection check testing.