Amendment to the June 20, 2013 “Risk Analysis of 

Disease Transmission between Domestic Sheep and 

Goats and Rocky Mountain Bighorn Sheep”, Shoshone 

National Forest

February 13, 2015

James M. Wilder, Shoshone NF Forest Biologist

This amendment to the June 20, 2013 Risk Analysis of Disease Transmission between Domestic Sheep 

and Goats and Rocky Mountain Bighorn Sheep was prepared as a result of direction from the Forest 

Service Chief’s Office to review any further literature that has come out since the June 2013 document 

was prepared. This direction was received in response to an objection to the Final Environmental Impact 

Statement (FEIS) and draft land management plan filed by the North American Pack Goat Association. 

The literature reviewed is listed in the Literature section of this amendment. The results of the literature 

review follow.

We reviewed 9 additional papers (listed below) on disease transmission from domestic sheep and goats 

to wild sheep.

• The central role of domestic sheep and goats in bighorn sheep exposure to pathogens is well 

documented; pathogen transmission from domestic to bighorn sheep is the only supported 

hypothesis in experimental trials. 

• Recent findings indicate that domestic goats also can carry other disease organisms with serious 

consequences for bighorn sheep. 

• Bighorn sheep (BHS) are more susceptible to developing fatal pneumonia than the related 

species Ovis aries (domestic sheep [DS]). 

• Outbreaks of bronchopneumonia in previously healthy populations of BHS often result in high 

death rates among all age groups initially, followed by years of impaired recruitment due to 

pneumonia in lambs. 

• Mannheimia haemolytica consistently causes fatal bronchopneumonia in bighorn sheep under 

natural and experimental conditions. 

• Odds of a pneumonia epizootic were >3.3 times greater if domestic sheep or goats are used for 

weed control in a BHS herd’s area of high risk (the area of each herd distribution plus a 14.5-km 

buffer from that boundary). 

• Contact with feral goats appears to result in BHS exposure to pathogens. 
• Risk of pneumonia epizootics is positively associated with greater amount of private land, weed 

control with domestic sheep and goats, history of a pneumonia epizootic in a herd or a nearby 

herd, and higher density. 

• Although the majority of bighorns in one study (Drew et al. 2014) were males, documented BHS 

contact with domestic sheep or goats did not correlate with either the bighorn breeding season 

or estrus in the domestic species.

• Management implications include the need for species separation and rapid responses to 

contact situations because 28% of the bighorns died with evidence of respiratory disease 

following domestic ruminant contact (Drew et al. 2014).

After review of these additional papers, the decisions made in the Forest Plan to restrict domestic 

sheep and goats, including pack goats, on the SNF remain unchanged. 
We reviewed the following additional papers to reach this determination.

Fox, K. A., Rouse, N. M., Huyvaert, K. P., Griffin, K. A., Killion, H. J., Jennings-Gaines, J., . . . Miller, M. W. 

(2015). Bighorn sheep (ovis canadensis) sinus tumors are associated with coinfections by potentially 

pathogenic bacteria in the upper respiratory tract. Journal of Wildlife Diseases, 51(1), 19-27. 

doi:http://dx.doi.org/10.7589/2014-05-130 

Sells, S. N., Mitchell, M. S., Nowak, J. J., Lukacs, P. M., Anderson, N. J., Ramsey, J. M., Gude, J. A. and 

Krausman, P. R. (2015), Modeling risk of pneumonia epizootics in bighorn sheep. The Journal of Wildlife 

Management, 79: 195–210. doi: 10.1002/jwmg.824 

Besser, T. E., Cassirer, E. F., Potter, K. A., Lahmers, K., Oaks, J. L., Shanthalingam, S., ... & Foreyt, W. J. 

(2014). Epizootic Pneumonia of Bighorn Sheep following Experimental Exposure to Mycoplasma 

ovipneumoniae. PloS one, 9(10), e110039. 

Drew, M. L., Rudolph, K. M., Ward, A., & Weiser, G. C. (2014). Health status and microbial 

(Pasteurellaceae) flora of free-ranging bighorn sheep following contact with domestic 

ruminants. Wildlife Society Bulletin, 38(2), 332-340.

O'brien, J. M., O'brien, C. S., MCcarthy, C., & Carpenter, T. E. (2014). Incorporating foray behavior into 

models estimating contact risk between bighorn sheep and areas occupied by domestic sheep. Wildlife 

Society Bulletin,38(2), 321-331. 

Shannon, J. M., Whiting, J. C., Larsen, R. T., Olson, D. D., Flinders, J. T., Smith, T. S., & Bowyer, R. T. 

(2014). Population response of reintroduced bighorn sheep after observed commingling with domestic 

sheep. European Journal of Wildlife Research, 60(5), 737-748.

Herndon, Caroline N., Sudarvili Shanthalingam, Donald P. Knowles, Douglas R. Call, and Subramaniam 

Srikumaran. 2011. Comparison of passively transferred antibodies in bighorn and domestic lambs 

reveals one factor in differential susceptibility of these species to Mannheimia haemolytica-induced 

pneumonia. Clinical and Vaccine Immunology 18, no. 7 (July): 1133-1138.

Miller, D. S., Weiser, G. C., Aune, K., Roeder, B., Atkinson, M., Anderson, N., ... & Clarke, P. R. (2011). 

Shared bacterial and viral respiratory agents in bighorn sheep (Ovis canadensis), domestic sheep (Ovis 

aries), and goats (Capra hircus) in Montana. Veterinary medicine international, 2011.

Wehausen, J. D., Kelley, S. T., & Ramey, R. R. (2011). Domestic sheep, bighorn sheep, and respiratory 

disease: a review of the experimental evidence. California Fish and Game, 97(1), 7-24.