Every year we test the 5 year old sheep for CL (Caseous lymphadenitis), OPP (Ovine Progressive Pneumonia), and Johnnes Disease. This year it was Iris (commercial Katahdin ewe) and Dazzle (Registered St Croix ewe)
Many years ago we had several problems in the flock and began testing. First for OPP, as it was cheaper, and culled all positives. Then the remaining sheep were tested for CL, also culling all positives. We continued testing until we came up with 3 all clear tests in a row. Now we test roughly 10-20% of the flock every year (and added Johnnes Disease testing) to keep ourselves on a clean status. Also tested are newcomers and any sheep having troubles (like abscesses, not keeping weight, etc).