Respiratory Disease threats for Bighorn and Thinhorn Sheep

The age of science on a continuum will continue to define wildlife health, risk and reward. Science evolves, and with every new advancement comes new insight into conservation of the wildlife species we have come to admire and respect. 

One defining mountain monarch rises above all the rest for this sheep hunter at heart, the Dall Sheep.

Wrangell Mountain 40in Dall Ram

As hunters, we are only as successful as our efforts to sustain and improve the populations we pursue. As science evolves, our task must too evolve. 

There is a new threat on the horizon for the prized Dall Sheep from Alaska through the Yukon and Northwest Territories. Severe and often fatal respiratory disease, encouraged by a microscopic pathogen called Mycoplasma ovipneumoniae (M. ovi). 

The Alaska Wild Sheep Foundation and the Yukon Government are leading the charge in raising awareness about this deadly exotic pathogen. Everyone that has an interest in the long term security of our wild sheep populations should listen up, learn more and get involved. 

Where does it come from? Innocuous cute and fuzzy domestic sheep and goats unfortunately. 

A little background on the topic for those unaware of the toxic effect M. ovi can have on wild sheep ~

OSU bighorn sheep research sheds light on path of killer disease

April 6, 2017

CORVALLIS, Ore. – With their ability to climb steep rocky mountain areas, California bighorn sheep live in some of the most rugged environments Oregon has to offer.

No matter how high they go, the wild sheep can’t elude Mycoplasma ovipneumoniae – the bacteria now widely thought to be primarily responsible for fatal infectious pneumonia in bighorns. Respiratory disease has killed numerous wild sheep in Oregon and other Western states over the past few decades and is considered the largest risk to wild sheep populations, according to the Oregon Department of Fish and Wildlife.

Once a herd is infected, an all-age die-off can occur, and the disease remains chronic in the population.

Now, Oregon State University researchers are studying several aspects of the California bighorn sheep herd in the state – including movement, habitat use and survival – to gain insight into the animal’s risk for contracting the killer strain known as M. ovi (pronounced m-ovee). The disease spreads through contact between domestic sheep flocks and bighorn sheep, or from bighorn to bighorn.

Oregon is home to about 3,700 California bighorn sheep in 32 different herds in central and southeast Oregon. ODFW traditionally captures and relocates California bighorn sheep around the state each year to improve genetic diversity and restore this rare species to its historic range in Oregon. But these relocation efforts are on hold this year while wildlife managers learn more about M. ovi, partly through the work being done at OSU.

Often, the first contact with a particular strain of pneumonia kills bighorn of all ages, according to OSU wildlife biologist Clint Epps. Some adults survive, but then as the infection persists their lambs die every year. A bighorn herd might not recover for decades.

Wildlife managers strive to keep wild and domestic sheep and goats separate to avoid transmission of the disease.

“There is a high-stakes need to understand where the pathogen is likely to enter a bighorn population and where it’s likely move after that,” Epps said. “In the past few years, wildlife agencies in the West have made decisions to remove certain individual animals, or all individuals in the herd, to prevent the spread of disease.”

A die-off of the bighorn sheep herd in the Lower Owhyee River Canyon in 2015-16 raised concerns about how M. ovi is impacting Oregon’s wild sheep populations. Also, that year the Nevada Department of Wildlife made the difficult choice to euthanize an entire herd of sick bighorn sheep just south of Oregon’s border to stop the spread of M. ovi to neighboring populations.

In 2011, ODFW had to kill five of the 20 bighorn sheep reintroduced to the John Day Fossil Beds after they wandered into an area where they could have been exposed to a domestic sheep farm.

“There’s been a tremendous amount of effort to increase these bighorn populations, and our goal is to provide better information when they make those decisions,” Epps said.

ODFW wildlife biologists and veterinarians have sampled and collared more than 120 California bighorn sheep in the past two years. Recent samples from those captured bighorn sheep, some of which were tested at OSU’s Veterinary Diagnostic Laboratory, will provide extensive information on diseases and animal health, including determining whether the strain that eliminated the Nevada herd has spread to Oregon’s bighorn sheep.

Robert Spaan, an OSU doctoral student, travels to southeastern Oregon from April to August to study the California bighorn sheep herds, which each typically number between 30 and 150 individuals. He tracks the bighorn sheep that have been fitted with GPS collars by ODFW and records birth and death data.

“We’re able to respond to mortalities, and we are able to determine cause of death in most cases,” Spaan said. “We managed to detect a die-off of lambs in one population last year, the only one where we saw active M. ovi infection.”

Disease was one of the factors when bighorn sheep died off in Oregon in 1940s, along with unregulated hunting. But sport hunters have since been instrumental in restoring bighorn sheep in Oregon. Oregon Department of Fish and Wildlife’s annual auction and raffle of special bighorn sheep tags have generated thousands of dollars for their management and for research.

Among the funders of the study are the Oregon Department of Fish and Wildlife and the Oregon Foundation for North American Wild Sheep.
Author: Chris Branam
Source: Clint Epps

If this isn't convincing enough as to the potential threat M. ovi poses to our white mountain monarchs of the north, here's a recent update from the Yukon that should bring it closer to home ~

Experts say risk of sheep transmitting disease ‘very real’

May 19, 2017

Rabbitfoot Canyon — that craggy split that divides downtown Whitehorse from Porter Creek — is the last place you would think to look for a wild sheep. But that’s exactly where Philip Merchant said they have turned up in the past.

“They were just standing there, watching the cars go past,” he said.

Merchant was the animal health coordinator with Environment Yukon for 10 years, a position from which he retired in 2011. He is, by his own admission, not a biologist or a veterinarian.
During his career, he said, it wasn’t just Rabbitfoot Canyon where wild sheep turned up unexpectedly but also in the Takhini River area near the sod farm, at Vista Road Tower, and even at the Grey Mountain rifle range, near the sheep silhouette targets.

This could have severe health implications for the species if they were to come in contact with domestic sheep, Merchant said.

“We have as good an idea of where wild sheep are as any jurisdiction, but we don’t know where they want to be,” he said.

As the News recently reported, there have been rising concerns among the conservationists, outfitters, environmentalists and farmers that domestic sheep and goats can spread pathogens to wild sheep. Those pathogens can cause severe — and often fatal — pneumonia.
This has occurred in southern populations of bighorn sheep, to which thinhorn sheep — a group comprised of three species and to which the Yukon’s famous all-white Dall sheep belong — are “very closely genetically related,” according to Environment Yukon ungulate biologist Troy Hegel.

An analogy might be grizzly bears and black bears, or mule deer and whitetails, Hegel said, referring to separate but closely-related species, which are often susceptible to the same infections.

Whereas domestic sheep can carry the bacteria with few or no health consequences, wild sheep have extremely limited resistance because they have never been exposed, said Hegel. Infected sheep either die, or, if they recover, have lingering health issues. Those that recover become “shedders” Hegel said, continuing to harbour the pathogen and infecting healthy members of the herd.

Although cross-species infection is well documented in bighorn sheep, there have been no documented cases of thinhorn sheep becoming infected from contact with domestic sheep. Merchant said there are “reams of data” that this is possible, and that infection has occurred in laboratory settings.

“The guy who was doing the experiment (on thinhorns) stopped his work because he said he was sick of killing sheep,” said Merchant. “You should never confuse the absence of evidence with evidence of absence.”

Hegel agrees the risk of infection to thinhorns is real.

“It’s a real risk — the probable outcome of the disease entering the wild population … there’s no doubt it would have a drastic effect on a population that’s been exposed,” he said.
People have been bringing sheep and goats into the Yukon for much longer than Environment Yukon has been around to do public awareness campaigns, however. This begs the question: If the disease is so contagious and dangerous, why haven’t there been infections — and die-offs — documented before?

“We don’t know this hasn’t occurred (already),” said Hegel. “If it happened 150 years ago, we might not even know.”

Thinhorn sheep have “high fidelity to range,” said Merchant, meaning that they often use the same grazing areas year after year, but we only understand their range “as we define it,” he said.

Animals may come down from the mountain in search of mineral licks, said Hegel, although these are usually routes which are well known to the animals. Small numbers of animals, particularly younger ones, may go “on a walkabout,” he said, where they wander off from their herd and either wind up back with their original population or assimilate into a new one.
These movements are a “key transmission risk,” said Hegel. If one of these wanderers were to come in contact with a domestic sheep carrying pneumonia-causing pathogens and become infected, it could spread the disease into the wild population when it returns to its range, Hegel said.

“They aren’t stuck on a mountain top their entire lives — there’s animals that are moving around,” he said. “These are the ones we are concerned with.”

This wandering behaviour explains the recent and much-talked-about incident of a young thinhorn ram who hopped a fence in Dawson City to visit some domestic sheep.

The ram paid for this casual encounter with its life.

“If a wild sheep comes in contact with a domestic sheep, the policy is to destroy it so that it can’t return to its native population,” said Hegel.

“All the reports have come in, and they’ve all said the same thing — do not let these animals mix in any way,” Merchant said. “That (ram is) the canary in the coal mine.”

“All the pieces of disease outbreak are here, they just haven’t come together yet. But they always do, given enough time.”

These concerns for wild populations have lead to discussions between agricultural and environmental officials and farmers, some of who feel unfairly pressured to meet recommendations to prevent interactions. These recommendations include double fencing, or adding electric fencing, a process which is expensive and labour-intensive.
There have been some calls to ban sheep and goats from the Yukon entirely, which is the way the Northwest Territories is going, said Merchant.

Hegel said that would be a “pretty significant, non-trivial” step for the Yukon.
Merchant said most people who own sheep and goats do not make their living from them, and that the number of sheep and goats in the Yukon is relatively small.

A 2015 flyer from the Animal Health Program entitled Preventing Pneumonia in Wild Sheep, recommends farmers “consider livestock other than sheep to raise fiber, milk and meat.”
“It’s a hobby — does somebody’s hobby have the right to threaten the public interest in conservation?” Merchant said. “Without the sheep, the mountains are just mountains — so I think that anything that could threaten them needs to be looked at.”

Shelia Alexandrovich of Wheaton River Garden said the idea that the eight sheep she raises are “just a hobby” is not a true. Alexandrovich has sheep for meat and milk, as well as for fibre, which she uses to make art and sells as part of her income.

“If I took away my ‘hobby,’ I would starve,” she said. “It provides 80 per cent of my food and 50 per cent of my income.”

“(Merchant) may see me as a hobby farm, but it’s what I do full time — I’m paid in food.”
Alexandrovich has lived in the Annie Lake area — thought to be some of the best wild sheep territory in the Yukon — for 37 years and has never once seen a wild sheep on her property, she said.

Hegel said this was possible, as there might might be other factors in the environment which discourage or prohibit the movement of the sheep onto the farm.

Merchant said the farm is “within one kilometre of where I would expect to see wild sheep.”
“If I thought I’d infect wild sheep, I’d double-fence in a minute — but I’ve never seen a wild sheep here,” Alexandrovich said. “If (the government) wants their concerns addressed — and it’s a legitimate concern — consult with farmers and give them the money to do (what’s been recommended).”

Alexandrovich said she didn’t feel the recommendations took into account the importance of small-scale farming and local food security.

“How on earth do you start (a farming industry) up here?” she said. “The little fellows trying to make inroads into local food … it isn’t easy.”

All in all, Hegel likens the recommendations to seatbelts.

“You can say ‘I never wear a seatbelt, I’ve been driving for 30 years, and I’ve never been in an accident,’” he said. “And then, suddenly, you’re in an accident and you really wish you’d been wearing a seatbelt.”

Author: Lori Garrison
Source: Yukon News

So where do we go from here? The first step is recognition of the problem and addressing the prevalence of M. ovi in local wild and domestic populations. To date, no M. ovi has been found in any thinhorn sheep population from northern British Columbia to the Brooks Range in Alaska. More animals need to be sampled, but so far, so good. 

In Alaska the Alaska WSF has worked with domestic producers and owners to encourage voluntary testing of their animals for M. ovi. Over the summer and fall of 2017, a significant number of domestic sheep and goats have been sampled, with more to go. Unfortunately M. ovi has been found in some of these samples, so now we move into the next stage - how to deal with the problem.

I respect the reference Troy Hegel made to the inevitability of pathogen transmission. Just because we have avoided any catastrophe thus far, doesn't mean we are immune from future transmission. It's this possible outcome we need to guard against in our pristine northern regions. Fully aware of the sensitivity of this issue given the disease vectors being cuddly little pets in some cases, there's a fine line between being pushy and responsible. Complacency is not an option. Let's solve this together, and keep our white mountain monarchs free of respiratory disease so that we may enjoy them for years to come.