Bighorn sheep

Baker County is home to two bighorn sheep herds. The photo above shows the California subspecies of bighorns in the Burnt River Canyon. The county’s biggest herd, numbering more than 300 animals, is in the Lookout Mountain unit. Those bighorns are the Rocky Mountain subspecies, and state biologists have determined that a strain of bacteria has infected some of the Lookout Mountain sheep, causing potentially fatal pneumonia.

Brian Ratliff is investigating a medical mystery that threatens the future of Baker County’s biggest herd of bighorn sheep.

Ratliff is the district wildlife biologist at the Oregon Department of Fish and Wildlife’s (ODFW) Baker City office.

His sleuthing has turned up some facts about the more than 300 Rocky Mountain bighorn sheep that roam the Lookout Mountain unit, which makes up of much of Baker County east and north of Interstate 84, extending to the Idaho border.

At least a handful of sheep have died over the past month or so from pneumonia caused by a strain of bacteria that had not previously been found in bighorns anywhere in Oregon, Ratliff said.

What’s not yet clear, he said, is how dangerous this strain is.

Of the more than 50 identified strains of Mycoplasma ovipneumoniae, some can eliminate an entire herd relatively rapidly, while others are comparatively mild and kill few animals, Ratliff said.

“I don’t know how bad it’s going to be,” he said Thursday.

The threat is serious enough, however, that ODFW this week canceled the two bighorn sheep hunts scheduled this summer and fall in the Lookout Mountain unit.

Those hunts included 3 tags — 2 for Oregon hunters and 1 for a non-resident.

“I’m always going to err on the side of caution,” Ratliff said.

Ratliff said he and other ODFW employees are regularly monitoring bighorns in the Lookout Mountain unit to try to gauge the lethality of the bacteria strain.

This is relatively easy to do because the bighorns, and in particular the ewes, lambs and young rams, tend to congregate in early spring along the Snake River Road between Huntington and Richland, where they graze on new grass.

“It’s a great viewing opportunity for the public, as these sheep are highly visible,” Ratliff said.

The investigation starts

The mystery dates to Feb. 13, when ODFW received a report of a dead bighorn ram on the Snake River Road near Connor Creek, about 18 miles north of Huntington.

Ratliff said samples from the sheep were tested, and the results showed the novel strain of bacteria.

There is no vaccine for the bacteria, nor any other type of effective treatment for such a large herd of wild animals, Ratliff said.

Biologists later euthanized a sick ewe, and a Washington lab confirmed the earlier diagnosis.

Because the bacteria strain is new to Oregon, the Lookout Mountain bighorns couldn’t have contracted the disease from other bighorns in the state, Ratliff said.

These types of bacteria are typically found in domestic sheep and goats, and Ratliff said he hopes to test animals that might have interacted with Lookout Mountain bighorns, although the source of the infection could be something else.

He can’t require livestock owners to comply, but he said he’s talked with some who seem willing to have their animals tested.

“It would be good to gain that information,” Ratliff said.

A factor that could complicate how ODFW deals with the pneumonia outbreak is that some bighorns will shed the bacteria constantly or intermittently — meaning they can infect others — while some sheep won’t shed.

Ratliff said he would like to be able to test as many bighorns as possible to determine which animals are constant or intermittent shedders. Depending on how many sheep die, it might be necessary in the future to euthanize shedders to preserve a herd that can be supplemented by bringing in bighorns from elsewhere.

That’s how the Lookout Mountain herd was established in the early 1990s, and the animals have thrived in the steep canyons on the breaks of the Snake River.

“It’s been the healthiest herd in Oregon,” Ratliff said.

The only previous concern among Lookout Mountain bighorns was a minor rash of pneumonia that lasted a couple months in 2012, he said. Those illnesses were caused by a virus rather bacteria, but it was a mild type that killed few bighorns, Ratliff said.

Previous outbreaks

Pneumonia outbreaks in other herds have been much more dire.

One of those eventually eliminated the Sheep Mountain bighorn herd that lived north of the Lookout Mountain herd.

The Sheep Mountain herd, which ODFW started with transplants in 1988, grew to nearly 100 sheep by the late 1990s, Ratliff said.

But then a ram from the herd crossed into Idaho, contracted viral pneumonia, returned to Oregon and infected the herd here.

By 2007 the Sheep Mountain herd was down to 10 animals — all ewes.

Because those sheep seemed immune, ODFW trapped a single ram in Wallowa County and released it on Sheep Mountain, hoping to start rebuilding the herd.

But that ram quickly died from pneumonia, proving that the ewes, though not ill, were still shedding the virus, Ratliff said.

In 2015, with just 3 ewes left, ODFW euthanized the remaining animals, he said.

The main concern was that the nearby Lookout Mountain herd, which was healthy and growing, would expand its territory and contract the illness from the Sheep Mountain animals.

Ratliff said he harbors a similar concern now.

The Lookout Mountain herd is close enough to represent a potential threat to Baker County’s other bighorn herd, which roams in the Burnt River Canyon southeast of Baker City, between Durkee and Bridgeport.

Although those bighorns are a different subspecies — California — they’re just as susceptible to viruses and bacteria that cause pneumonia, Ratliff said.

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