On Jul. 16, 2024, Colorado Parks and Wildlife officials announced the first finding of ‘rustrela virus’ in a mountain lion in North America. The study, published in the journal “Emerging Infectious Diseases,” reported that officials had to euthanize a sick mountain lion in Douglas County in May 2023 that was unable to use its hind legs.

An analysis of tissues from the mountain lion revealed the presence of the rustrela virus, which was identified as the cause of “staggering disease,” a usually fatal neurologic syndrome recognized in domestic cats. Scientists do not know how widespread the virus is in either domestic cats or wildlife populations. In Europe, rustrela virus causes staggering disease in cats, but also has been found in a wide range of other species, including rodents, a donkey and marsupials.