Range conditions need to be monitored. It is a disease-ecology issue and is not simplistic. In addition, there are other less common diseases involved such as contagious ecthyma or sore mouth in Missouri Breaks 622 and pinkeye or conjunctivitis in the Yellowstone Park herd. Other agents are muscle worm, psoroptic mange and coccidiosis. There was a decline evident in the Mickey-Brandon Buttes area of 622.
Treatment has to be done judiciously.
Congestion of animals needs to be minimized and it all has to be monitored. This is being done with success in the Highlands and Upper Rock Creek. You don't want to pre-treat herds as you can select for drug resistant lungworm. You treat only if you are sure of the disease. The integrity of the herd needs to be preserved and nature has to be able to do some culling for individuals with strong natural immunity.