A New Threat to North American Wildcats: The Unraveling Mystery of Rustrela Virus
The natural world, even in the heartland of the United States, holds hidden dangers. Recently, a chilling discovery has brought a new, and potentially devastating, threat to the forefront: rustrela virus, a previously unknown pathogen that has now been found in a mountain lion in Colorado. This discovery marks the first confirmed case of staggering disease, a debilitating and often fatal neurological illness in cats, in the United States.
The story begins in May 2023, when Colorado Parks and Wildlife officials received reports of a weakened mountain lion exhibiting unusual symptoms. The creature, found near a residential area in Douglas County, Colorado, had lost the use of its hind legs, dragging itself with its front limbs. After tranquilizing the animal, officials were forced to euthanize it to preserve its brain for further study.
Initial tests for common causes of neurological problems in cats, such as rabies virus and Toxoplasma gondii, yielded negative results. However, a meticulous genetic analysis of the mountain lion’s brain and spinal tissue revealed the presence of rustrela virus, formally known as Rubivirus strelense.
This virus is a relative newcomer to the scientific world, first identified in 2020 in animals at a German zoo experiencing neurological disorders. The discovery was published in the prestigious journal, Nature, in October 2020. Then, in February 2023, researchers from another study, also published in Nature, confirmed rustrela virus as the causative agent of staggering disease in European cats.
While rare, staggering disease has been known to affect both domestic and wild felines in Europe since the 1970s. The findings in the Colorado mountain lion, published in the journal Emerging Infectious Diseases, mark the first documented case of rustrela virus and staggering disease in North America.
This discovery raises alarming questions. Notably, the rustrela virus strain isolated from the mountain lion is genetically distinct from those found in Europe, suggesting the possibility of a North American endemic strain. Furthermore, the wide range of mammals that rustrela virus can infect remains unclear. While currently there is no evidence to suggest that it can infect humans, it is closely related to the rubella virus, which can cause rare neurological problems in humans. Notably, rubella, also known as German measles, was eliminated in the United States in 2004 thanks to successful vaccination programs.
Despite the unknowns, this discovery is crucial for understanding and potentially mitigating the potential threat posed by rustrela virus. "Considering its wide host range in Europe, rustrela virus should be considered as a cause for neurologic diseases among mammal species in North America," wrote the researchers.
The urgency of this situation is not lost on scientists. "Now that we know what we’re looking for, it should be easier to find new cases if they are out there," said lead report author Karen Fox, a former pathologist with Colorado Parks and Wildlife. "With continued collaboration, we plan to learn what we can from our colleagues in Europe while we continue to look for new cases of staggering disease here in Colorado."
While research continues, public awareness and vigilance are crucial. Residents in Colorado are being encouraged to report any sightings of similarly sick mountain lions to their local wildlife officers. This proactive approach, combined with the expertise of researchers, offers the best hope for understanding and addressing this emerging threat.
The discovery of rustrela virus in a North American wild cat serves as a stark reminder of the complex and interconnected nature of ecosystems and the potential for previously unknown pathogens to emerge. This is not just a story about a sick mountain lion; it is about the fragile balance of nature and the imperative for scientific research, public vigilance, and collaborative efforts to ensure the health of both wildlife and humans.
