Pneumonia in Bighorn Sheep: Background

Pneumonia is a bacterial respiratory disease observed in bighorn sheep. It is thought that bighorn sheep can contract the disease through direct contact with domestic livestock. There are two bacterial agents responsible for pneumonia in Arizona’s bighorn sheep, Manheimia hemolytica and Mycoplasma ovipneumoniae.

The amount of infection can vary within a herd and cause mortality in more than 90% of the infected animals. Animals that do not die may become carriers, putting naïve lambs at risk. In these cases, the number of lambs that reach adulthood is reduced such that the overall herd size declines for several years. Several states have reported severe losses in bighorn sheep populations with the disease.