Interaction with domestic sheep and goats maybe linked to bighorn sheep populations developing pneumonia. Pneumonia in bighorn sheep is often fatal and can affect all age groups within a herd.
Preliminary disease mortality estimates range from 50-80% of individuals within affected herds. The potential exists for surviving bighorn sheep to serve as carriers, and populations that experience outbreaks subsequently have low recruitment of lambs, as reported by South Dakota’s Custer State Park. A variety of bacterial pathogens have previously been identified in the pneumoniacomplex, including Mycoplasma spp., Pasturella multocida, Pasturella trehalosi, and Mannheimia haemolytica, in addition to respiratory viruses and lungworm infections. Pneumonia is a challenging issue for bighorn sheep managers because of the difficulty associated with identifying the disease agent, remote locations, and limited management options.
--National Wildlife Health Center Newsletter