Johne’s Disease

Guernsey cow with weight loss typical of  clinical Johne’s disease.

Pronounced “Yo-knees”, Johne’s disease is also known as paratuberculosis.  This bacterial disease primarily affects the small intestines of cattle and other ruminants.  There is no vaccination and no treatment for Johne’s.

The bacterium, mycobacterium avium subspecies paratuberculosis, is primarily spread between animals through feces.  In cool, wet environments the bacterium can survive up to a year in feces in and around a barnyard.  It can also be passed by an infected cow through colostrum, milk and can transmit in utero.  Animals less than 6 months of age are the most susceptible to being infected by the bacterium.  Unfortunately, the clinical symptoms may not be seen until two or more years after the initial infection.  This is especially concerning for seedstock producers raising animals to sell for breeding.  An infected animal can also shed the bacterium without showing clinical symptoms.  Clinical signs of the disease include diarrhea and weight loss despite a normal appetite.  The bacterium  causes the intestinal walls to thicken, reducing the absorption of nutrients.

There are several preventative measures that can be taken to help reduce the spread of Johne’s.  Directly from the Montana Department of Livestock: “1. Implement a biosecurity plan that identifies sources of disease risk and strategies to avoid disease introduction.  2. Inquire about the Johne’s status of a herd when purchasing new animals; important consideration must be given to bulls because they are with cows at a time that calves are highly susceptible.  3. Raise newborns in a clean environment.  4. Avoid manure contamination of feed and water sources.  5. Identify and remove infected animals.  6. Maximize disease resistance through good nutrition and parasite control.  7. Pasteurize pooled milk fed to calves.”

Diagnosis of Johne’s according to the Montana Department of Livestock: “1. Herd screening tests and diagnostic individual animal tests are available. 2. Blood, feces, and/or tissues can be tested.  3. Testing programs should address both clinically ill animals as well as sub clinically infected animals (asymptomatic carriers of bacteria.)”

To help mitigate the spread of Johne’s, the Department of Livestock has developed a program to: “Minimize the spread of Johne’s disease through animal sales and movement.  Identify positive animals/herds and implement management practices to eliminate the disease.  Support non-infected herds by identifying biosecurity practices to prevent the introduction of the disease into their herds.  Create a market opportunity for participating herds to advertise their involvement in the program.”

For more information, please contact the MSU Extension office, your local veterinarian, or the Montana Department of Livestock at