A wild animal was found struggling to stand and walk in a Colorado yard last summer — and biologists now know why, according to a new study.
The mountain lion was suffering from rustrela virus, which causes “ ‘staggering disease,’ a usually fatal neurologic syndrome recognized in domestic cats,” Colorado Parks and Wildlife said in a July 16 news release.
It’s the first case of the disease found in a mountain lion in North America, the agency said.
The virus has been commonly found in domestic cats in Europe since the 1970s, according to a study published this week in the Centers for Disease Control and Prevention journal Emerging Infectious Diseases.
The sick mountain lion was spotted in someone’s yard in Douglas County in May 2023, officials said. The young animal was unable to use her hind legs, and wildlife officials euthanized her.
“The animal was reluctant to rise and had markedly decreased capacity to move or bear weight on the hind end,” the study says. “The animal moved by pulling itself forward with the front legs, while minimally propelling itself forward with the hind legs.”
Video shows the mountain lion hobbling forward with her front legs as she struggled to use her back legs to stand and walk.
“Other features of the animal’s gait include swaying of the hips, slight head tremors, and repeated collapse,” the study says under the video. “The animal appeared depressed but was still responsive to stimuli.”
Wildlife officers tranquilized the mountain lion and killed her with a gunshot to the chest “to prevent destruction of neurologic tissues” so scientists could study those tissues, the study said.
The sick mountain lion was in pretty poor physical condition, and her brain and spinal cord tissue revealed the presence of a variation of the rustrela virus distinct from the strain found in Europe, the study said.
The lead author on the paper, former CPW wildlife pathologist Dr. Karen Fox, said the team collaborated with German researchers to determine the variant still caused staggering disease in the mountain lion, officials said.
Fox said diagnosing staggering disease in the mountain lion was “challenging, and final confirmation was only possible through collaboration with researchers at the Friedrich-Leoffler-Institut in Germany,” officials said.
Fox is now a research scientist with Colorado State University. She “emphasized that scientists don’t yet know how widespread the virus is in either domestic cats or wildlife populations.”
Rustrela virus causes staggering disease in cats in Europe and has also been found in several other species, “including rodents, a donkey and marsupials,” officials said. But the variant found in the mountain lion was new.
“Now that we know what we’re looking for, it should be easier to find new cases if they are out there,” Fox said.
Researchers will continue collaborating with their colleagues in Europe while looking for new cases of staggering disease in Colorado, officials said.
