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Johne's Disease (Paratuberculosis)

Johne's disease, or Paratuberculosis, is a chronic infection of the intestinal tract of ruminants. Infections have been found in cattle, sheep, goats and some species of wild ruminants. Johne's disease is caused by a species of bacteria known as Mycobacterium Paratuberculosis.

How is this infection spread?

The major known method of spread is fecal-oral; this means the animal usually ingests the bacteria through feed or water contaminated with infected feces. In calves, this may occur when they first nurse their dam. Apparently, there is an age-related resistance to Johne's Disease. Calves under one year old are most susceptible. Older heifers are less susceptible and adult cows are resistant to infection. Other possible, though less common, routes of infection include semen (via natural service) and pregnant dam to fetus (in utero).

How widespread is Johne's Disease?

The exact answer to this question is unknown. For example, separate slaughter surveys have indicated that as few as 2 percent to as many as 17 percent of culled Ohio cattle may be infected with Mycobacterium Paratuberculosis. While many individual herds are undoubtedly free of infection, some herds may harbor the infectious agent in 50 percent of the adult animals.

What are the signs of Johne's Disease?

Following exposure, some animals apparently "clear" the bacteria and remain totally free of infection. Others may become infected and periodically shed bacteria in their feces but never develop clinical signs of the disease. Some herds, however, may lose 5-10 percent of their adult cattle annually to clinical Johne's.

For those cattle that are exposed and eventually develop clinical signs, Johne's Disease is different than many other diseases. The time from exposure to development of signs is long and may range from 1-13 years. It is common for heifers to develop Johne's signs following the stress of the first or second freshening.

The initial clinical sign is the development of diarrhea. The diarrhea may be either continuous or of an intermittent nature. In addition to diarrhea, there is extreme weight loss and, eventually, death. Some animals may have a low-grade fever and develop edema under the jaw as diarrhea progresses. There is some evidence which indicates that animals with subclinical Johne's (i.e. without diarrhea) may experience reduced milk production and suboptimal fertility.

How do I know if Johne's Disease is in my herd?

Obtaining a rapid, reliable diagnosis is possibly the major problem in controlling Johne's Disease. Basing the diagnosis of a herd entirely on clinical signs could be misleading. Other disease agents can cause a similar type of diarrhea. Furthermore, an animal could be shedding Johne's bacteria (Mycobacterium Paratuberculosis) in its feces, contaminating the environment, yet be visibly normal.

Currently, the most reliable diagnostic test is the bacteriologic culture of feces. A drawback to the fecal culture is that is doesn't allow detection of infected animals that are not shedding bacteria. Another drawback is the time it takes to determine the results, 12-18 weeks.

Two serum tests, AGID and ELISA are available; currently, both have serious shortcomings. The AGID test is very accurate when an animal has clinical Johne's, and many veterinarians use AGID to obtain an early diagnosis on a suspect diarrheic animal. This test has a 48 hour turnaround; an advantage over the 12-18 week time-lag with fecal cultures. For use in herd control programs, AGID is not sensitive when an animal is infected but visibly normal: AGID is likely to misclassify a shedding or non-shedding animal that is still clinically normal as negative.

The ELISA tests currently available falsely classify some noninfected animals as infected and some infected animals as noninfected. Hopefully, improvements in test methods and standardization will enhance the usefulness of the ELISA.

In the future, other improved tests may be developed for practical use in diagnosis. For example, DNA probes for detection of Mycobacterium Paratuberculosis in feces have been developed and used experimentally. At this time (September 1988), work is being completed to determine how applicable DNA probes will be for diagnostic use and in herd control programs.

How resistant is Mycobacterium Paratuberculosis to treatment?

The Johne's bacteria is very resistant to antibiotics. Treatment of animals with Johne's is not advisable. Generally, the most economically sound decision is to market clinically affected cattle as soon as possible. Johne's infected cattle will usually pass slaughter if they are not severely thin or debilitated.

In the environment, Mycobacterium Paratuberculoses is extremely hardy. It can survive in soil, manure and water for more than a year. It is resistant to many common disinfectants. On clean surfaces, however, it is quickly destroyed by direct sunlight. As with most other infectious diseases, there is no substitute for cleanliness when considering Johne's control.

Is there a vaccine available?

A vaccine is available. In Ohio, it must be administered by an accredited veterinarian. Permission and guidelines for its use on a farm must be obtained from the State Veterinarian. The vaccine helps reduce shedding of bacteria and clinical signs when coupled with good management. The vaccine will not totally prevent infection, however. As with many other diseases, vaccination may be a portion of a disease control or reduction program but not the total answer.

Does Ohio have an eradication or control program?

No official federal or Ohio programs exist at the present time. Several other states do have programs in place. Most programs, in addition to stressing hygiene and management, rely upon periodic fecal culturing to identify shedding animals and subsequent culling of these animals from the herd. Some states allow vaccination; others do not. It is too early to tell how effective these programs will be.

What if Johne's Disease is diagnosed in my herd?

First assess the probability or extent of additional infected animals present in your herd. For example, was the affected cow purchased as a springing heifer or raised as a natural addition to your herd? If she was home-raised, given the fact that infection occurs early in life, there is a likelihood that additional herd mates have been exposed. If she was purchased as a springer and not exposed to your farm's young stock it is possible that spread may not have occurred. Your veterinarian may or may not recommend additional herd testing at the time of the initial diagnosis depending on the circumstances.

Total eradication of Johne's, given currently available diagnostic tests and knowledge, may not be economically feasible in commercial herds. However, a more intensive intervention program may be warranted in herds that merchandise breeding stock. Herds that can demonstrate test-negative status may command premiums on animals offered for sale or export. Regardless of your herd's present infection status, institution of a control or prevention program does make economic sense in all dairy herds.

Reduce exposure of susceptible animals. In any Johne's control or eradication program, complete commitment and cooperation between herd owners, managers, caretakers and veterinarians is vital.

Management Recommendations for Control of Johne's Disease in a Dairy Herd.

  1. To reduce environmental contamination, identify and remove from the herd those adults that are shedding Mycobacterium Paratuberculosis. Fecal culture, although not perfect, is the diagnostic test favored at this time as it is the only test that identifies shedders. The extent and pattern of culturing in a herd is best determined by consultation with your veterinarian.
  2. Freshen in a sanitary area—outside is best, weather permitting. Remove the calf from its dam as soon as possible. Don't let the calf nurse. Hand feed colostrum obtained from a thoroughly cleaned udder. Using milk replacer may lower the exposure of young calves in infected herds. Alternatively, some large herds have installed pasteurizers to use on discard milk for feeding calves.
  3. Raise young stock away from adults. Remember that adults are possible carriers of infective bacteria and that animals less than 12 months old are susceptible. Have a separate person care for the calves or feed them before handling the adult animals. Break the habit of feeding calves after the morning milking.
  4. The bacteria that causes Johne's is hardy and is spread through manure from adult cattle. Do not spread manure on pastures or graze heifers on pastures previously used by adults. Watch drainage from adult barnyards to heifer lots or heifer water supplies. Fence off ponds that have become contaminated by barnyard drainage.
  5. Isolate unthrifty animals or animals showing diarrhea. Work closely with your veterinarian to obtain an accurate diagnosis of all diseases.
  6. High risk animals. Progeny from infected cows should be regarded at greater risk of being infected themselves and considered for potential culling or at least for greater surveillance. Exposure during the birth process is likely and the possibility of intrauterine infection of the fetus exists. The consequences of fetal infection are not yet known.
  7. If you don't have Johne's Disease in your herd DON'T BUY IT. For the prevention of Johne's and other contagious diseases it makes good sense to use Artificial Insemination. If you do purchase bulls or replacement females, know as much about the source as possible. At least two national breed organizations have instituted programs designed to reduce the chances of purchasing an infected animal. In other cases, screen testing of the seller's herd prior to purchase has been advocated by some experts. However, if you do purchase stock, maintain these animals away from your own young stock and institute recommendations 1-5 above.

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This page was last updated on November 16, 2002