Johne's disease, or Paratuberculosis, is a chronic (years) mycobacterial infection affecting primarily the lower small intestine of many ruminants. Infections have been found in cattle, sheep, goats, llamas and some species of non-domestic ruminants (deer, bison). Johne's disease usually refers to the clinical condition associated with infection from the organism Mycobacterium paratuberculosis.

Clinical signs in cattle, include profuse watery diarrhea, weight loss, and lowered milk production. Appetite will stay the same or increase. Some animals may have a low-grade fever, and develop edema under the jaw (bottle jaw).

What causes Johne's Disease?

The causative agent of Johne's disease M. paratuberculosis is an acid-fast bacterium related to other tuberculosis organisms. Mycobacterium paratuberculosis was first isolated in 1895 by Dr. Heinrich Albert Johne. The name "Johne's" disease (pronounced "yo-knees") resulted. Like other mycobacteria, this is a slow-growing organism requiring 12-16 weeks to grow in the laboratory under "ideal" conditions.

How does Johne's Disease occur?

The animals in a herd most likely to become infected are new born calves. Animals usually ingest the bacteria through feed or water contaminated with infected feces, or from bacteria on the teat or udder of the cow. Calves can also become infected while in the uterus of a positive cow, or they can ingest bacteria which can be passed in the colostrum or milk. The risk of any of these three routes of infection is higher as the cow enters more advanced stages of the disease.

After infection, the bacteria grow slowly in the intestinal cells and cause a gradual thickening of the intestinal wall. These changes keep the cells from doing their job, resulting in weight loss and diarrhea.

Who is Susceptible to Johne's infection?

Newborn calves, or young animals are the most susceptible animals in a herd. While animals develop some resistance with age, individual animals of any age can be infected if there are enough bacteria in the environment. All ruminants can become infected with the disease.

When does clinical Johne's Disease develop?

Even though animals are infected at a very young age, clinical disease rarely occurs before 2 years of age. Typically, clinical symptoms occur after the first or second lactation. Animals exposed between 18 and 24 months of age, or animals exposed to a very small amount of the organism, likely will not develop clinical disease until they are older. This may even be 8 - 10 years of age.Prior to clinical signs, these animals may be shedding the organism into the environment. The 2 most important factors determining when clinical disease develops are: a) an animal's age when first infected and b) the dose of amount of the organism ingested. It has been observed that animals living under better husbandry conditions tolerate the infection better. It would appear that some stress factor is involved in causing the cow to become clinical.

The Four Stages of Johne's Disease in Cattle

Stage I - Silent, subclinical, non-detectable infection - typically this stage occurs in calves, and heifers less than two years of age or animals exposed to a small dose of bacteria. There are currently no tests on the market to detect or identify these animals. Eventually, these animals progress to Stage II.

Stage II - Subclinical shedders typically involving older heifers or adults. These animals may appear healthy, but are shedding enough M. paratuberculosis organisms in their manure to be detected on fecal culture. By shedding organisms, these animals are contaminating the environment. Blood testing may or may not be reliable in detecting these animals.

Stage III - Clinical Johne's disease - any animal with advanced infection, which may have been brought on by a period of stress. These cattle have acute or intermittent, watery , fetid manure. A loss of weight and a drop in milk production are also common signs. Many of these animals continue to eat, and are positive on serologic tests. Signs may last from a few days to a few weeks before these animals progress on to Stage IV.

Stage IV - Advanced Clinical Johne's Disease - This is the end stage of this disease. Most animals are very thin with fluid diarrhea. Some animals can progress from Stage II to Stage IV in a few weeks.

"The Iceberg Phenomenon"

For every Stage IV cow in your herd expect:

Stage III.    Clinically diseased    1 - 2 cows

Stage II.    Inapparent carrier adults    6 - 8 cows

Stage I.    Calves - youngstock    10 -15 calves

For every animal obviously infected, there are 15 - 25 other animals that are very likely infected.

If the infection remains unchecked, the rate and number of infected animals in the herd increases over time. Early diagnosis and prevention of spread, before multiple clinical cases surface, can avoid Johne's developing into a significant herd problem in five to ten years.

How is Johne's Disease determined?

While the fecal culture remains the best test on a live animal, it requires 12 - 16 weeks of culture time (and is expensive). Serologic tests are more rapid, probably best used on a whole herd basis, but may be less accurate. A more rapid test may be important in some situations. For further information regarding tests, please contact your local veterinarian, or call the Ohio Department of Agriculture at 614-728-6220.

Economic losses attributed to Johne's

The economic impact of Johne's disease in a herd may include some or all of the following effects:

Surveys have indicated that Johne's disease is also prevalent in many other states that have looked including Wisconsin, New York, Maryland, Pennsylvania, Virginia, Illinois, Texas, Florida, Connecticut and California. Johne's is a reportable disease in 33 states.

How is Johne's disease controlled on the farm?

THERE IS NO TREATMENT FOR JOHNE'S

The key to controlling this disease is prevention. The key to prevention is MANAGEMENT. Testing needs to be one part of a total commitment to eliminating the disease from the herd. Testing will provide the following information:

Once the extent of the problem is identified, appropriate management and sanitation procedures will need to be put in place to accomplish the following goals:

Specific recommendations: The specifics and intensity of a Johne's disease control strategy in cattle will vary with the individual farm situation. To be relevant and effective it must be designed to fit the immediate and future goals of the farm, and available resources. Although many specific methods can be used, they must involve some or all of the following:

Management of newborn calves and young animals is critical and is the most effective place to put the effort.

Calves should be born in an area that is dry, clean of manure, and well bedded. Clean teats and udders are a must. The calving area needs to be restricted and used strictly for maternity. It is best if you can remove newborn calves from the dam immediately, eliminating the chance to ingest manure in attempts to find the udder and nurse.

Feed newborns colostrum, ideally within one to two hours, from only healthy appearing dams, who are less likely to pass M. paratuberculosis into the udder and milk.

Milk replacer eliminates the risk of possible infection from feeding whole or pooled milk to calves. Replacer should be seriously considered especially in herds with significant infection.

Young calves and heifers should be housed separate from adults and should have no direct contact with manure from adult cattle. Separate facilities are ideal but sections protected by partitions, dry alleyways or buffer zones, or low traffic zones are effective.

DO NOT contaminate feed or feed mangers with manure from feet or equipment.

Management to prevent low levels of exposure in all older animals is important:

Prevent manure contamination of feed and waterers. DO NOT use the same loader or equipment to clean manure and to load feed. DO NOT walk in the feed bunks. Eliminate or fence animals out of natural water sources that they drink, that are also slow moving or stagnant, and collect run-off containing manure that animals stand in.

SANITATION has no substitute. Remove manure as thoroughly and often as possible. Always strive for more often. Spread manure on cropland, not on pasture to be harvested or grazed the same season.

Identifying and removing infected animals and their manure is necessary to reduce the risk of continued exposure for ALL animals.

Test the herd to identify infected animals that are, or probably will be shedding the bacteria. Based on the evaluation of results, infected animals should be culled as heavily as economics permit. The most severe should be culled first.

Manage all animals as if they are infected, and all manure as if guilty. This management attitude works all the time, and is especially important if testing and early culling is not practical.

Reduce the risk of introducing infected animals into the herd, especially when elimination of the infection is the goal.

Be cautious and investigate animals to be purchased. Purchase animals from test negative herds, or, in discussions with the owner, confirm the herd has no history of Johne's. Reduce risk by prior testing with serology or by fecal culture immediately when animals arrive.

Goals of a Johne's Disease control program.

In herds with low to moderate infection (one percent or fewer clinical cases per year) wise use of a combination of testing, culling and MANAGEMENT can be expected to reduce the clinical disease to zero within 1 to 3 years and most infection in 5 to 7 years. Thus, as the herd turns over, each succeeding generation will have fewer infected animals, eventually all of which will be non-shedders. Complete elimination of infected cattle is likely to take many years after Johne's disease becomes invisible in the herd. PREVENTIVE MANAGEMENT should remain in place otherwise Johne's disease is likely to recur.

Herds with more severe widespread infection will require aggressive control programs and many years to eliminate Johne's disease.