The bacteria mycobacterium avium paratuberculosis causes a chronic intestinal infection in cattle and other ruminants commonly known as Johne’s Disease. The bacteria grows slowly and it takes years after the initial infection before the animal develops clinical signs. The animal’s well-being and genetic potential are compromised during that subclinical time. It’s possible that cattle leaving the herd as “poor-doers” were infected with mycobacterium avium paratuberculosis.
Perhaps it has been awhile since Johne’s Disease was thought of as a threat to beef herds, but Johne’s is still the silent thief it has always been. According to the “National Animal Health Monitoring Survey in Johne’s” study from 2008, data estimated that 8 percent of U.S. beef herds and 68 percent of dairy herds contain at least one animal infected with the bacteria. Although there are not any current prevalence estimates, prevalence has likely increased because of ongoing movement of animals with unknown status into herds.
Determine herd prevalence by working with a veterinarian to complete the Risk Assessment Management Program. The Wisconsin Department of Agriculture, Trade and Consumer Protection recommendations follow those instituted by the U.S. Department of Agriculture’s Voluntary Johne’s Disease Control Program.
Control and prevention begins with assessing the management practices and conditions that promote the risk for spread of Johne’s Disease and other fecal-oral- and colostrum-milk-transmitted pathogens. The risk assessment scores these practices, with scores heavily weighted to calf management. Beef calves, with their close and long proximity to adults in the herd, make them especially vulnerable to infected individuals’ manure.
Biosecurity practices are also scored. Purchased herd additions, including bulls, should ideally come from status-documented herds. Sources with known testing history at the herd level that demonstrate a low risk for Johne’s disease are the next best option for herd additions. Do not purchase cattle from untested source herds.
Testing is the last aspect for managing this disease. Testing plans are developed in response to the identified risks and ultimate goals of the farm. First have a plan in place for how to use test results. Otherwise testing is of limited value.
Work with a veterinarian to determine the best testing options for a herd. The testing protocol designed for seed-stock raisers is different than the protocol used by those managing a cow-calf herd. The testing used also depends upon the test purpose. The testing protocol used to eradicate this disease from the herd is different than that used for confirming a clinical diagnosis. Testing protocols differ depending upon if the herd has or does not have prior confirmed cases.
Testing required for official herd classification is different from surveillance testing. Those working to control the disease in a herd with known infection and established prevalence may want to include environmental surveillance to estimate the biological burden on the farm.
Prevention and control involves planning and practicing the plan. Planning begins with learning. An easy free opportunity to aid learning is available at the University of Wisconsin School of Veterinary Medicine Johne’s Information Center. Visit johnes.org or datcp.wi.gov for more information.