Pneumonia hits bighorn sheep in Hells Canyon; die-offs likely

Hells Canyon bighorn sheep pneumonia

Wildlife officials in Oregon, Washington and Idaho are monitoring a pneumonia outbreak affecting bighorn sheep in Hells Canyon along the Snake River and tributaries. Exposure to the bacteria responsible is known to lead to die-offs in bighorn sheep populations.

The Oregon Department of Fish and Wildlife (ODFW) said the outbreak was detected in mid-December and is ongoing.

“The bacterium responsible for the pneumonia outbreak is Mycoplasma ovipneumoniae, commonly referred to as ‘Movi,'” ODFW said. “Exposure of bighorn sheep populations to Movi is usually followed by a die-off. The severity of these die-offs can vary, with population declines ranging from 5 to 100 percent. On average, about 50 percent of the population survives the initial die-off. More information is being gathered to understand the severity of the die-off.”

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ODFW said this is one of several pneumonia outbreaks in bighorn sheep that have occurred over the past century in Hells Canyon, which spans 652,000 acres in northeastern Oregon and western Idaho.

“Unfortunately, there is no way to treat animals to slow the spread of disease or reduce deaths,” said Frances Cassirer, Senior Wildlife Research Biologist with the Idaho Department of Fish and Game. “Our best option is to let the disease run its course over the next several months and then reassess the situation. At that point our objectives are to restore the health of those populations that are affected and prevent further spread among the interconnected populations throughout Hells Canyon and the surrounding area.”


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