The bacteria Mycobacterium avium paratuberculosis (MAP) causes a chronic intestinal infection in cattle and other ruminants commonly known as Johne’s Disease. MAP 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 this subclinical time. It is very possible that cattle leaving your herd as ‘poor-doers’ were infected with MAP.
Perhaps it has been awhile since you last thought about Johne’s Disease as a threat to your beef herd; but Johne’s is still the silent thief it has always been. Older data estimated that 8% of U.S. beef herds and 68% of dairy herds contain at least one animal infected with MAP (National Animal Health Monitoring Survey, Johne’s study from 2008). Although we do not have current prevalence estimates, prevalence has likely increased because of ongoing movement of animals with unknown status into herds.
You can determine your herd prevalence by working with your veterinarian to complete the Risk Assessment Management Program (RAMP). Information about RAMP is available from the Wisconsin Department of Agriculture Trade and Consumer Protection, https://datcp.wi.gov/Pages/Programs_Services/JohnesDisease.aspx and https://datcp.wi.gov/Documents/PreventionControlBeef.pdf . DATCP recommendations follow those instituted by USDA Voluntary Johne’s Disease Control Program. View the national uniform program standards at https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/nvap/NVAP-Reference-Guide/Control-and-Eradication/Johnes-Disease.
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. Ideally, purchased herd additions (including bulls) should 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 your 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 the test results; otherwise testing is of limited value.
Work with your veterinarian to determine the best testing options for your herd. The testing protocol designed for seedstock raisers is different than the protocol used those managing a cow-calf herd. The testing used also depends upon the purpose for the test. For example, the testing protocol used to eradicate this disease from the herd is different from 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.
Written by Sandy Stuttgen, DVM, UW Extension Agriculture Educator, Taylor County and recently appeared in Wisconsin Agriculturist magazine.