In December 2023, wildlife officials detected pneumonia in bighorn sheep in the northern Hells Canyon. Now, over a month later, the outbreak is considered ongoing and has the potential to infect bighorn sheep populations along the Snake River and its tributaries, according to a news release.

“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 (IDFG).

IDFG is working with the Washington Department of Fish and Game and the Oregon Department of Fish and Wildlife to keep tabs on how widespread the outbreak is and do what they can to address the situation.

“Our best option is to let the disease run its course over the next several months and then reassess the situation,” said Cassirer. “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.”

This particular outbreak is linked to the Mycoplasma ovipneumoniae bacteria, which causes die-offs in infected sheep populations. Usually, only 50% of an infected herd survives this type of epidemic. This is one of several pneumonia outbreaks that have occurred in the Hells Canyon area over the past century, according to the news release.

Anyone who observes a dead or sick bighorn sheep should contact their local state fish and wildlife agency to report it.