Colorado Parks and Wildlife/Courtesy Photo
When Colorado Parks and Wildlife euthanized a cougar in Douglas County last year, there was no explanation for what had left the predator so crippled and disoriented that it could barely move.
Video captured by a homeowner on May 12, 2023, showed the cougar dragging itself on the ground on its front legs, struggling to stand as it staggered forward. A postmortem examination of the cougar reportedly found no skeletal abnormalities that could explain its lameness.
Now, just over a year after the 1-year-old lioness was reported to Colorado Parks and Wildlife, scientists say they’ve discovered the cause of her ailment: a baffling disease, a usually fatal neurological syndrome found in domestic cats in Europe.
It’s the first time scientists have found the rustrela virus, recently identified as the cause of a baffling illness, in a North American mountain lion, according to a study published this week in the journal “Emerging Infectious Diseases.”
The paper’s lead author, Dr. Karen Fox, said in a press release that diagnosing this baffling disease was challenging and that definitive confirmation was only possible through collaboration with researchers at the Friedrich-Loeffler-Institut in Germany.
Fox, a researcher in the Colorado State University Department of Veterinary Medicine and Biomedical Sciences in Fort Collins, was also previously a pathologist with Colorado Parks and Wildlife.
Scientists do not yet know how widespread the virus is among domestic cats or wildlife in Colorado. In Europe, rustrela virus causes a staggering illness in cats, but it has reportedly been found in a variety of other species, including rodents, a donkey and marsupials.
The “remarkably broad range” of other mammals that can host rustrelavirus, or RusV, raises concerns that the virus could spread between people and animals, although that has not yet been studied, the study said.
“Given the wide host range of the virus in Europe, RusV should be considered a potential cause of neurological disease in all mammalian species in North America,” the study said.
The study suggests that research should be conducted on small rodents in Colorado to determine whether these rodents could be reservoir hosts, or carriers of the virus that do not suffer adverse effects.
Veterinarians from Colorado State University and Colorado Parks and Wildlife will also be closely monitoring for new cases, according to a news release from the agency. If members of the public see cougars staggering, having difficulty walking or acting abnormally, they should contact their local Colorado Parks and Wildlife office to report the behavior, the news release said.
“Now that we know what we’re looking for, it should be easier to find new cases when they occur,” Fox said in a statement. “With continued collaboration, we plan to learn what we can from our colleagues in Europe as we continue to search for new cases of vertigo here in Colorado.”