New CAST Commentary Addresses Respiratory Disease in Sheep

August 12, 2008

For Immediate Release

August 12, 2008…Ames, Iowa. Disease has contributed significantly to the decline of bighorn sheep populations throughout much of western North America, decreasing many native herds to less than 10% of their historical size. Although native sheep are particularly susceptible to pneumonia, and interactions between wild and domestic species seem to carry some risk for disease spread, not all contemporary pasteurellosis epidemics in bighorn sheep can be attributed to contact with domestic populations. To evaluate current knowledge on this issue and highlight needs for further research, the Council for Agricultural Science and Technology (CAST) is releasing a new CAST Commentary, Pasteurellosis Transmission Risks between Domestic and Wild Sheep.

Specific topics discussed in the new Commentary include:

“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, Wildlife Research Center, Fort Collins. “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.”

CAST Executive Vice President John M. Bonner concludes, “CAST’s latest Commentary reflects the combined experience and insight of the Task Force of eight scientists. CAST is pleased to present this document as a contribution to the body of scientific knowledge on this important subject. Other recent CAST publications have addressed the international risks of infectious animal diseases, such as avian influenza, as they relate to humans. And we are considering future papers on the interactions among diseases and domestic animals, wild animals, caged wild animals, and human health.”

The full text of Pasteurellosis Transmission Risks between Domestic and Wild Sheep (CAST Commentary QTA 2008-1) will be available online without charge beginning August 12, 2008 at the CAST website (, along with many of CAST’s other scientific publications. 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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Dr. Michael W. Miller: Phone: 970-472-4348; E-mail:
Dr. John M. Bonner—Phone: 515-292-2125, ext. 25; E-mail:

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