Article by  By: Dr. Melanie Hemenway, DVM NYSCHAP Coordinator

What is Johne's Disease?

Johne's disease is a chronic, incurable bacterial infection that primarily affects the lower small intestine of ruminants.  Infection most commonly occurs when young animals ingest the bacteria Mycobacterium avium paratuberculosis (MAP).  After infection, the bacteria grow slowly inside the animal's intestinal cells.  Over time, the animal's immune cells multiply in response to the bacteria's presence, eventually leading to thickening of the intestine, impairing the ability to absorb nutrients, and leading to the clinical signs of Johne's disease in some animals.  The disease progression in the small intestine may take up to two to six years or more before late stage clinical signs are seen.  These signs include weight loss, intermittent or continuous unresponsive diarrhea, but a normal appetite.  Some animals develop "bottle jaw" - fluid under the jaw caused by protein loss.  Late stage animals continue to deteriorate and can die in a few days or a few months.

There are no good estimates of prevalence in beef herds in the United States.  A NAHMS survey in 1997 showed less than 10% of beef cow/calf operations positive for Johnes, however, this is considered a very conservative number based on the survey design and the lack of registered operations being a part of the survey.  Johne's disease is a herd problem that worsens with time, reducing production and profit.  

Johne's disease has the largest impact on seedstock and purebred producers since they are selling animals that will be kept long enough for an animal to break with the disease.  These are the operations that should be more motivated to do something about the disease especially when it is perhaps at a more lower, manageable level in their herd.  The operations who do implement Johne's control will have a distinct advantage in marketing their breeding stock.

Johne's is primarily transmitted through the fecal-oral route and that is where management needs to focus.  Also, young animals less than 6 months of age especially the newborns are the most susceptible to infection so they are the ones to protect against exposure.  It may be difficult but not complex to prevent new infections.  We are not going to tell beef producers to take calves away from their mothers like we recommend in the dairy industry.  However, we can institute management that takes new cow-calf pairs and puts them in a clean environment to minimize spread.  Also, we encourage producers to get feed off the ground and use bunks or racks to minimize manure contamination as well as fence off surface water sources and use water tanks which are cleaned regularly.  Also, beef operations can utilize Johne's testing to identify late stage infected animals for culling and more intense management to control the exposure of the manure from these animals to young stock.

Critical management points for Johne's disease control: Reduce infections by manure management (all manure is suspect) - Avoid manure build up in pastures, corrals and barns.  Have a clean calving area and move new cow/calf pairs to a clean pasture as soon as possible.  Avoid keeping high risk or sick cows in the calving area and avoid overcrowding.  Provide clean feed for all cattle and avoid manure contamination by using feed bunks and/or hay racks.  Use separate equipment to hand manure and feed.  Provide clean water, not contaminated by potentially infected animals.  Keep adult cow manure away from young stock by housing in separate facilities or pastures not recently used by adult cattle.  Prevent transporting bacteria to young stock by people, runoff and equipment. Reduce infections by colostrum management - Feed "low risk" colostrum from test negative cows.  If colostrum supplementation is needed use clean harvesting procedures or consider using a quality commercial colostrum supplement product. Reduce infections by managing infected animals - Identify and remove clinical and late state animals immediately.  Consider Johne's testing to identify subclinical animals and define herd status.  Johne's testing can also help identify infected animals that are shedding Johne's in their manure.  These animals can be culled or segregated away from the herd and especially the young animals to help minimize spread in the environment.   Purchased animals - Do not buy from herds with unknown Johne's infection status.  Obtain herd health information from source herds ask about their Johne's disease monitoring and management.  Pretesting purchases will not detect Johne's infections in the early stages of the disease so additional follow up tests are recommended two or three times at six to twelve month intervals.  

Johne's Disease Control Program New York State offers cattle producers a free program - the New York State Cattle Health Assurance Program (NYSCHAP).  This is a voluntary disease management program that helps farms identify disease risks, create obtainable goals and implement strategic herd planning that works within the farm's resources to meet their goals.  The program uses a team approach bringing together the farmer, the herd veterinarian and a NYSCHAP herd planner who is either a NYS veterinarian or a NYSCHAP certified private veterinarian.  The program pays the herd veterinarian for their participation so there is no cost to the producer.  Also, enrollment in NYSCHAP allows farms to receive subsidized pricing for Johne's testing.  This program can tailor an effective plan for Johne's identification, control and testing for the farm.  More information on the program and how to enroll can be found on the NYSCHAP website:  www.nyschap.vet.cornell.edu. 

Guernsey cow with clinical Johne's disease (paratuberculosis), showing significant weight loss. Photo by Dr. Michael T. Collins. Click to enlarge.