CAST Weighs in on Bighorn Sheep Disease

Bighorn sheep populations are at the center of high profile and controversial issues across the Western United States between federal land management agencies, state game agencies and domestic sheep ranchers. As a game species, bighorn sheep are prized by many game departments; however, health issues are a concern in a number of the herds. Too frequently, the producers of domestic sheep find their ranches and grazing allotments brought into the discussions of protecting the wild sheep at the expense of domestic sheep grazing.

The Council for Agricultural Science and Technology (CAST) released this week in its peer-reviewed commentary, Pasteurellosis Transmission Risks between Domestic and Wild Sheep, findings that state that native sheep are particularly susceptible to pneumonia. Interactions between wild and domestic species seem to carry some risk for disease spread, yet not all contemporary pasteurellosis epidemics in bighorn sheep can be attributed to contact with domestic populations.

"Even though there's been considerable scientific effort directed toward this topic, precisely quantifying the risk of interspecies disease transmission between wild sheep and domestic sheep in a natural setting is problematic," says Task Force Chair Michael W. Miller, National Wildlife Research Center, Fort Collins, Colo. "Consequently, a broad approach to population health management seems to be the most practical way to decrease the overall likelihood of epidemics in wild sheep populations."

Such an approach includes, but does not rely solely on, practices that prevent interactions between wild and domestic sheep that could result in respiratory pathogen transmission. Preventing contact between wild and domestic sheep, better monitoring of exchanges and interactions between separate wild sheep populations, and managing population and habitat quality all have some value in improving and maintaining the overall health of wild sheep populations and preventing pneumonia epidemics.

Ongoing and planned research also is likely to provide a better understanding and new tools that may further improve approaches for wild and domestic sheep health management on native ranges.

American Sheep Industry Association Resource Management Council co-chairs, Clint Krebs (Ore.) and Bill Taliaferro (Wyo.), are actively engaged in the industries efforts in regard to bighorn sheep given the vast share of domestic sheep production in the states most involved with the bighorn sheep.

"This report is appreciated for the balance of recommendations offered," stated Krebs.

The full text of the commentary is available at www.cast-science.org/displayProductDetails.asp?idProduct=156.

CAST is an international consortium of 37 scientific and professional societies. It assembles, interprets and communicates credible, science-based information regionally, nationally and internationally to legislators, regulators, policymakers, the media, the private sector and the public.

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