The most common pathogens in bighorn sheep are respiratory bacteria Pasteurella haemolytica or Pasteurella multocida, and Mycoplasma ovipneumonia but respiratory viruses like Infectious Bovine Rhinovirus, Parainfluenza virus, Bovine Respiratory Syncytial Virus, or parasites like lungworms can contribute to pneumonia in bighorns and other ruminants. There is evidence in captive and free-ranging bighorn sheep that transmission can occur after contact with domestic sheep or goats. Other ruminants can develop pneumonia from these and other bacteria including Arcanobacter spp., Corynebacterium pseudotuberculosis, and Trueprella pyogenes as well as a variety of respiratory viruses.
Signs Of Disease
Clinical signs of pneumonia in ruminants include coughing, shortness of breath, and a weakened condition. Generally, animals with pneumonia will have discolored lungs possibly with adhesions to the rib cage or abscesses. In trials of captive bighorn sheep that are inoculated with Pasteurellaceae bacteria, survival is generally less than 2-3 days. Depending on the bacterial pathogen present, the nutritional and immune status of the individual, and other factors, affects range from chronic pneumonia in adult females, summer lamb mortality events and ill thrift to rapid whole herd mortality events . Often the mortality events are found by hunters or during herd surveys when carcasses or skeletons are found. Similar signs of disease occur in other ruminants affected by pneumonia but pneumonia in other species of ruminants tends to occur in single individuals rather than on a herd basis.
Where is Disease Found?
Generally, pneumonia is a problem in bighorn sheep and to a lesser extent in deer and elk. Pneumonia in bighorn sheep has been found throughout North America. In Idaho, pneumonia in bighorns has been found in all areas where bighorn sheep exist. Isolated cases of pneumonia have been documented in mule deer, white-tailed deer, elk, moose, pronghorn and mountain goats in Idaho.
How Can I Protect Myself?
The bacteria that cause pneumonia in ruminants is not considered a human health hazard. Domestic sheep and goats can carry some of the respiratory pathogens that result in illness or death of bighorn sheep; therefore, appropriate management to maintain temporal and spatial separation of domestic sheep and goats from bighorn sheep is important. Contact between domestic sheep and goats and bighorn sheep will trigger a response by IDFG to remove the bighorn sheep from the interaction site. Wear rubber or latex gloves when handling animals that have been harvested especially if signs of pneumonia are present.
Samples to Collect
Take photographs of the lungs of sick or dead ruminants. If possible, nasal and oral swabs, and a piece of lung tissue about the size of a golf ball could be collected, placed in a plastic bag and kept cold or refrigerated until delivered to a conservation officer or an Idaho Department of Fish and Game Regional Office. Dry nasal swabs for Mycoplasma spp. can be collected and frozen for submission to an appropriate diagnostic laboratory. Nasal and oropharyngeal swabs can be placed in specific bacterial transport media, refrigerated and shipped to an appropriate diagnostic laboratory within 48-72 hours after collection. In dead ruminants, pieces of lung tissue the size of a dice can be collected, placed in a plastic bag, and refrigerated or frozen until submission to an appropriate diagnostic laboratory. Carcasses can be frozen until delivered to an appropriate diagnostic laboratory.
Can I Eat The Meat?
The meat animals that have pneumonia can be consumed by humans. If the animal has active disease with purulent material in the lungs (abscesses) or is unthrifty, the meat should not be consumed by humans.
What is IDFG doing to help manage this disease?:

Idaho Department of Fish and Game conducts surveillance of bighorn sheep populations for the pathogens associated with pneumonia whenever bighorn sheep are captured or handled. Herd performance is monitored for evidence of lamb mortality events. Interactions between domestic sheep and goats and bighorn sheep trigger a response by Idaho Department of Fish and Game to remove the bighorn sheep from the interaction site. The Idaho Department of Fish and Game is conducting or collaborating on research on bighorn sheep disease with numerous academic and research institutions.

Pneumonia in other ruminant species is sporadic and does not appear to affect populations.