Ag Notes, Dec. 19

Published 8:39 am Tuesday, December 19, 2017

Early detection is key to keep Johne’s disease from taking over your beef herd

Johne’s, pronounced Yo-knees, disease is a chronic disease of severe, watery diarrhea and weight loss in adult cattle caused by a bacterium. These bacteria are very hardy due to a protective cell wall that can withstand harsh conditions and allows survival for long periods in the environment. Once the bacteria gain entry into an animal, the organism lives permanently within the cells of the large intestine where it multiplies and is then “shed” in the feces in large numbers. Johne’s is a slow, progressive disease that calves pick up around the time they are born but the clinical signs of weight loss and diarrhea do not show up until much later, generally at two to five years of age or even older.

As cow/calf producers, it is easy to buy and sell breeding-age animals, especially bulls, with no obvious problems even though they are already infected with the disease. The problem is difficult to detect early, but infected animals often shed high numbers of the MAP organism on the farm. In ideal conditions with moisture and limited sunlight, bacteria can live eight months in dry feces, nine to 12 months in a manure pit/lagoon, 18 months in a water trough,  nine to 12 months in freezing temperatures and one or more years on pasture. This is important because the major route of transmission to newborn calves is nursing teats covered in Johne’s-infected manure. A small number of calves may get the disease while still in the uterus of an infected cow or may ingest the organism from infected colostrum or milk. Once infected, there is a long incubation period, sometimes two to seven years, then the disease begins to progress from a silent stage to an advanced disease stage. No effective treatment is available.

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In a typical herd, for every animal in the advanced or clinical stage of disease, often there are many other cattle in earlier stages of the disease. Control measures center upon preventing exposure of susceptible animals to the infectious agent, identifying and eliminating infected animals from the herd and preventing entry of infected animals into the herd. With early diagnosis and prevention of spread, Johne’s disease will not develop into a significant herd problem five to ten years in the future.

Buyers of breeding livestock should make every effort to purchase animals that are not MAP infected. Similarly, seedstock producers should anticipate this request and establish a routine of testing and culling any cattle that test positive for the organism. Seedstock herd owners are commonly reluctant to test for Johne’s disease for fear that a positive diagnosis will ruin their reputation. However, a herd’s reputation may be damaged much more severely by selling an infected animal to a customer and introducing this contagious, incurable disease into the buyer’s herd. The U.S. Voluntary Bovine Johne’s Disease Control Program specifies the testing requirements to officially classify a herd from Test Negative Level 1 (lowest) up to Level 6 (best). The more years of testing following this consistent regimen will yield greater confidence and knowledge of the true Johne’s status of the herd.

So how do you begin? A screening test of all animals at least two years of age, such as the Johne’s ELISA test for antibodies in blood, is rapid and low cost but not 100 percent accurate. Any positive animals on ELISA should be confirmed by detection of the Johne’s bacterium in the feces by polymerase chain reaction. Both of these tests are available at the UK Veterinary Diagnostic Laboratory. For more information, visit their website Animals found positive should be removed from the herd promptly. Testing and culling over multiple years along with good herd management will lead to zero or low MAP test prevalence in your herd. Contact your local veterinarian to find out more about the control and prevention of Johne’s disease.

For more information on livestock diseases and management, contact the Boyle County Cooperative Extension Service.

Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of economic or social status and will not discriminate on the basis of race, color, ethnic origin, national origin, creed, religion, political belief, sex, sexual orientation, gender identity, gender expression, pregnancy, marital status, genetic information, age, veteran status, or physical or mental disability.

Jerry Little, County Extension Agent for Agriculture/Natural Resources