Johne's Disease is a disease of the intestinal tract of cattle and other ruminants.
It is caused by the bacteria Mycobacterium paratuberculosis, an acid fast bacteria very similar to the organism that causes tuberculosis in man and animals.
The organism M. paratuberculosis, however, only causes intestinal disease in ruminants.
The greatest economic impact occurs in cattle, even though sheep, goats, llamas, and possibly other ruminants may also become infected and exhibit symptoms.
The organism is passed through the feces of infected animals. It will remain infective in contaminated feed, water, pasture, and equipment for extended times, as it is resistant to many disinfectants and environmental factors.
Occasionally, infection may occur in calves before birth or from the milk after birth. Infection occurs by swallowing contaminated material, most commonly fecal material on the teats of the young animal's dam. Even with initial infection occurring at a very early age, the incubation period is very long and symptoms occur at
about two years, with peak period of symptoms becoming obvious at three to six years of age or older.
The organism grows within the cells of the lining of the intestine and will be shed in the feces of both animals showing symptoms and those not showing symptoms. Because of the long incubation period and slow development of the disease, thereby making it difficult to identify carrier animals, the economic impact of
the disease is especially high to the cattle industry.
This article includes other clinical signs of the disease such as diarrhea, weight loss and others. It also includes diagnosis of the disease which the article say it more difficult due to the long incubation. However it suggest testing can be done through the CF test (Complement fixation) and the enzyme-linked immunoassay (ELISA) test for herd screening, with the limitations of each.
Another test recommended is the DNA probe, which tests feces and is requires expensive, highly specialised equipment.
The last part of the article features prevention and control measures as well as its increasing prevalence in cattle in the state of Oklahoma.
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Article made possible through the contribution of the Oklahoma State University, Oklahoma Cooperative Extension Service.