Bighorn Sheep Respiratory Disease and Nasal Tumors

Since the late 19th century, respiratory disease has been identified as a leading cause of population declines in bighorn sheep in the western United States.  This disease in bighorn sheep is characterized by sporadic outbreaks of bronchopneumonia in all ages of bighorn sheep.  Disease is commonly followed by multiple years of poor lamb survival.  The cause of disease is most likely multifactorial, including bacterial, viral, parasitic, and environmental (stress, nutrition) factors.  The interactions between these causes aren't completely understood nor are any predisposing conditions. 

In the winter of 1990/1991 the Whiskey Mountain herd suffered an all-age die-off caused by pneumonia, resulting in an estimated 30% decline in the number of sheep.  The herd continues to stay below the desired population size primarily because lamb survival is very low likely due to the persistence of lamb pneumonia.  At one time, there were an estimated 2,500 sheep in this population; today there are about 750.
Since 2012, the Wyoming Game and Fish Deaprtment has been conducting statewide bighorn sheep herd health surveillance.  Currently we have sampled 966 bighorn sheep and 59 mountain goats.  The purpose of this surveillance is the determine 'herd health' status/baseline for each herd (e.g. trace minerals, parasites, pregnancy rate, etc.).  In addition we document all respiratory pathogens and potentially correlate pathogen presence to heard health.  Respiratory disease in bighorn sheep is polymicrobial, with the common pathogens found in most Wyoming herds being Mannheimia haemolytica, Bibersteinia trehalosi (Lkt+), Pasteurella multocida, and Mycoplasma ovipneumoniae.

Signs exhibited by animals suffering from respiratory disease include, but are not limited to: coughing, head shaking, nasal discharge, respiratory distress, exercise intolerance, and general depression.  Animals are often just found dead.


                                                                                    coughing bighorn sheep


Bighorn sheep project in Jackson, WY

Nasal Tumors in Bighorn Sheep

Nasal tumors in bighorn sheep were first characterized in Colorado in 2009.  Non nasal tumors have been described in bighorn sheep since the early 1990's.  Although a specific etiologic agent has not been identified, research has shown the agent to be infectious.  Nasal tumors have been identified in eleven of Wyoming's bighorn sheep herds, and is suspected in two.  Nasal tumors in bighorn sheep are fatal as there is currently no treatment. 



Suspected nasal tumors erupting from bighorn sheep skull - courtesy of Dr. Kevin Montieth - University of Wyoming

Captive Research

Since 2013, the Wyoming Game and Fish Department has also conducted bighorn sheep respiratory pathogen research at Thorne-Wiliams Wildlife Research Center.  Research projects have been conducted independantly as well as in collaboration with Colorado Parks and Wildlife and Washington State University. 


If you observe a bighorn sheep in the wild exhibiting signs of respiratory disease, i.e coughing, head shaking, nasal discharge, respiratory distress, exercise intolerance, or general depression; or if you find a carcass please notify the closest Wyoming Game and Fish Department Regional office, or area biologist/game warden. 

If harvesting a bighorn sheep, consider donating unusable portion of skull to the Wyoming Game and Fish Department for nasal tumor research.


Wyoming Bighorn Sheep Surviellance 2016-2018 Report
Wyoming Bighorn/Domestic Sheep Ineraction Working Group
Wyoming Cooperative Fish and Wildlife Research Unit Collaborative Research
National Bighorn Sheep Center - Dubois Wyoming
Whiskey Mountain Bighorn Sheep Plan


Lowrey, Blake, Carson J. Butler, William H. Edwards, Mary E. Wood, Sarah R. Dewey, Gary L. Fralick, Jessica Jennings-Gaines et al. "A survey of bacterial respiratory pathogens in native and introduced mountain goats (Oreamnos americanus)." Journal of wildlife diseases 54, no. 4 (2018): 852-858.

Butler, C. J., Edwards, W. H., Paterson, J. T., Proffitt, K. M., Jennings-Gaines, J. E., Killion, H. J., ... & McWhirter, D. E. (2018). Respiratory pathogens and their association with population performance in Montana and Wyoming bighorn sheep populations. PloS one, 13(11), e0207780.

Killion, H. J., Edwards, W., Jennings-Gaines, J., Wood, M., Fox, K., & Sondgeroth, K. (2018). Development and validation of a real-time PCR specific for the leukotoxin gene of Bibersteinia trehalosi. Journal of Veterinary Diagnostic Investigation, 1040638717753497.

Grigg, J. L., Wolfe, L. L., Fox, K. A., Killion, H. J., Jennings-Gaines, J., Miller, M. W., & P. Dreher, B. (2017). Assessing Timing and Causes of Neonatal Lamb Losses in a Bighorn Sheep (Ovis canadensis canadensis) Herd via Use of Vaginal Implant Transmitters. Journal of wildlife diseases, 53(3), 596-601.
Butler CJ, Edwards WH, Jennings-Gaines JE, Killion HJ, Wood ME, McWhirter DE, Paterson JT, Proffitt KM, Almberg ES, White PJ, Rotella JJ. Assessing respiratory pathogen communities in bighorn sheep populations: Sampling realities, challenges, and improvements. PloS one. 2017 Jul 14;12(7):e0180689.
Wood ME, Fox KA, Jennings-Gaines J, Killion HJ, Amundson S, Miller MW, Edwards WH. How Respiratory Pathogens Contribute to Lamb Mortality in a Poorly Performing Bighorn Sheep (Ovis canadensis) Herd. Journal of Wildlife Diseases. 2017 Jan;53(1):126-30.

Jennings-Gaines J, Edwards WH, Wood MA, Fox KA, Wolfe LL, Miller MW, Killion HJ. An improved method for culturing Mycoplasma ovipneumoniae from field samples. In Biennial Symposium of the Northern Wild Sheep and Goat Council 2016 (Vol. 20, pp. 83-88). Cody, Wyo, USA: Northern Wild Sheep and Goat Council.

Walsh DP, Cassirer EF, Bonds MD, Brown DR, Edwards WH, Weiser GC, Drew ML, Briggs RE, Fox KA, Miller MW, Shanthalingam S. Concordance in diagnostic testing for respiratory pathogens of bighorn sheep. Wildlife Society Bulletin. 2016 Dec 1;40(4):634-42.

Fox KA, Rouse NM, Huyvaert KP, Griffin KA, Killion HJ, Jennings-Gaines J, Edwards WH, Quackenbush SL, Miller MW. Bighorn sheep (Ovis canadensis) sinus tumors are associated with coinfections by potentially pathogenic bacteria in the upper respiratory tract. Journal of wildlife diseases. 2015 Jan;51(1):19-27.

Kardos M, Luikart G, Bunch R, Dewey S, Edwards W, McWilliam S, Stephenson J, Allendorf FW, Hogg JT, Kijas J. Wholeā€genome resequencing uncovers molecular signatures of natural and sexual selection in wild bighorn sheep. Molecular ecology. 2015 Nov 1;24(22):5616-32.

Shanthalingam S, Goldy A, Bavananthasivam J, Subramaniam R, Batra SA, Kugadas A, Raghavan B, Dassanayake RP, Jennings-Gaines JE, Killion HJ, Edwards WH. PCR assay detects Mannheimia haemolytica in culture-negative pneumonic lung tissues of bighorn sheep (Ovis canadensis) from outbreaks in the western USA, 2009–2010. Journal of wildlife diseases. 2014 Jan;50(1):1-0.

Miller MW, Hause BM, Killion HJ, Fox KA, Edwards WH, Wolfe LL. Phylogenetic and epidemiologic relationships among Pasteurellaceae from Colorado bighorn sheep herds. Journal of wildlife diseases. 2013 Jul;49(3):653-60.

Email Newsletter

Email Newsletter Sign Up

Stay up to date on all Wyoming Game and Fish news either by email or text message. Click the link below to get started.

Sign Up Today


Conserving Wildlife - Serving People