Herd certification is loosely defined on this web page as any official program designed to classify flocks according to the probability that individual sheep in those herds are infected with Mycobacterium avium subspecies paratuberculosis (MAP).
The primary aim of certification programs is two-fold:
- Provide a simple system to communicate to sheep buyers the risk of buying a MAP-infected animal.
- Stop the spread of this infection to non-infected flocks. Flock certification is the foundation of paratuberculosis prevention.
Johne’s disease should be considered a flock health problem, not just an individual animal disease. Certification programs apply laboratory tests to classify flocks by levels of infection ranging from not infected at all to very likely MAP-infected. Often such programs have regulations that participating herd owners must follow regarding the sources for replacement animals. These rules are designed to help herd owners avoid bringing MAP-infected sheep into their herds without compromising their ability to do business.
The schematic diagram above illustrate these two basic concepts: 1) apply a herd test to sort the herds (flocks) and 2) prevent movement of infected sheep into the non-infected flocks. Of course, this works best if all flocks participate and is only achievable with one application of a test to all flocks if the test was perfect. Lacking perfect tests, we must repeat testing annually.
NOTE: In this graphic, the term “national herd” does not have to represent all the sheep flocks in a country. It can just as easily represent all of the flocks in a specific locale or of a specific breed. Breed associations can adopt these same principles to stop the ongoing spread of Johne’s disease among their elite breeders: it’s the right thing to do for the health and welfare of their animals and their organization.
Check out the Beef/Certification page of this site to see an examples of a sound certification / herd classification program designed for U.S. cattle.
Follow this link to see the extensive program designed for sheep in Australia.