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JACKSON — The first plague-infected cat was a kitten that turned up dead in the high country between Ditch Creek and the Gros Ventre River some 14 years ago.

Biologist Howard Quigley, who was then directing an upstart Teton Cougar Project, remembers that the flea-transmitted disease was not on the short list of suspected causes.

“We didn’t really think about plague at that time,” Quigley said. “In fact, it was in the middle of winter, and we thought maybe it starved to death or had some kind of winter stress.”

Today researchers realize that plague among Greater Yellowstone Ecosystem cats isn’t all that uncommon. In fact, nearly half of lions in the southern part of the region appear to have been exposed to the disease, and more than a third of dead cats tested carried it.

Those figures come from a close examination of mountain lions in east-central Jackson Hole over nine years that the Teton Cougar Project tested all dead cats for plague. Results of a study authored by Quigley, Mark Elbroch and veterinarian Winston Vickers were recently published in the academic journal Environmental Conservation.

“The overall prevalence of exposure we recorded was similar to that found along the western slope of Colorado, which is adjacent to the Four Corners region, a known plague hotspot in the [United States],” the researchers wrote.

Plague is a zoonotic, viral disease spread by a bacterium, Yersinia pestis. It’s the same disease responsible for the infamous “Black Death” in the 14th century that killed tens of millions of people in Europe and beyond.

Based on the Cougar Project’s research, there was a rash of plague around 2006 that rippled through the local population of felids. Three of the four lions killed by plague turned up dead that year, and the only other that died of the disease was in 2010. Cats with exposure and antibodies to plague were tested in 2007, 2008, 2010 and 2013.

The four cats that died of plague totaled 6.6% of the dead cats recovered during the study period. That’s not enough to have a “population-level effect” in itself, Quigley said, but it’s one cause of death among many — wolves, hunting, starvation, etc. — that have helped lion biologists understand the cumulative mortality pressures weighing on Jackson Hole’s cats.

“You start to get a clear picture of how hard it is to be a mountain lion in Jackson Hole,” Quiqley said. “If you get to be an adult mountain lion in Jackson Hole, you’re a survivor.”

Felids as a family of mammals are notorious carriers of plague, which is on rare occasion picked up by humans. An average of seven cases a year are confirmed in the United States. In Wyoming there have been six cases since 1978, according to the Wyoming Department of Health. The last was in 2008, when a teenage Boy Scout on a service trip in the Jackson Hole area was diagnosed, treated and fully recovered. He was with a group that camped on an elk feedground and had stayed in Grant Village at one point, according to the Jackson Hole Daily archives.

While the risk of most humans contracting plague from a cougar is almost zero, hunters and researchers should be aware that the disease has been present in the Greater Yellowstone Ecosystem cats in the past, and that interspecies transmission has happened before. Elbroch wrote in a recent blog post that his friend and mentor, Eric York, died from plague contracted from a Grand Canyon National Park lion in 2007.

“His terrible death reverberated through the research community, causing shock and mourning,” Elbroch wrote. “And it could have been avoided if people had considered the possibility that he had plague and administered appropriate antibiotics.”

After York’s death, Teton Cougar Project biologists and technicians started keeping a closer eye on each other after handling cats, Quigley recalled.

Quigley and Elbroch today work for the international large cat conservation organization Panthera. Quigley is the group’s conservation science executive director, and Elbroch is the lead scientist of its Puma Program.

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