Rustrela virus variant identified in Colorado

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A recent study published in the August issue of the Emerging Infectious Diseases journal shared that researchers identified a rustrela virus (RusV) variant in a wild mountain lion in Colorado. These findings mark the first documented case of rustrela virus associated “staggering disease” in North America. According to the American Veterinary Medical Association (AVMA),¹ staggering disease is an often-fatal neurologic condition that has posed a threat to domestic felines in Europe for several decades, especially in Austria and Sweden. Staggering disease has also bee recently linked by scientists to RusV, a relative of the rubella virus that causes German measles in people.

The researchers in the study reported that in May 2023, a 1-year-old, free range female mountain lion was euthanized by the Colorado Parks and Wildlife (CPW) officials in Douglas County after it received a report that she was presenting with severe hind leg ataxia and paresis.² When the officials arrived, the mountain lion appeared to be depressed and was reluctant to rise and had markedly decreased capacity to move or bear weight on the hind end. After the euthanasia, a subsequent tissue analysis revealed the presence of RusV.¹

When it comes to staggering disease, the most common clinic sign is hind-limb ataxia with generally increased muscle tone, which causes a stagger in the animal’s gait. There is also a range of other clinic signs that can occur, including the inability to retract claws, hyperesthesia, and occasionally tremors and seizures. Infected animals can also present with behavioral changes such as depression, increased affection, and enhanced vocalization, and in rare cases, aggression. The disease can usually last a few days to weeks but could continue for a year and it generally results in deterioration that requires euthanize for welfare reasons.

At this time, scientists do not know how widespread RusV is in domestic cats or wildlife. RusV causes staggering disease in cats, but also other species such as rodents, a donkey, and marsupials in Europe. Surveillance for the virus in small rodents could potentially identify a local reservoir host because rodents of the genus Apodemus were identified as likely viral reservoir hosts. However, Apodemus rodents are not indigenous to North America but there are multiple genera of small rodents within Colorado that could serve as candidates for further screening. Future studies should also consider that the zoonotic potential of RusV is not determined at this time.

“Given the wide host range of the virus in Europe, RusV should be considered as a possible cause for neurologic diseases in all mammal species in North America,” the article’s authors concluded.²

References

1. Staggering disease’ discovered in Colorado mountain lion. News release. American Veterinary Medical Association. August 15, 2024. Accessed August 21, 2024. https://www.avma.org/news/staggering-disease-discovered-colorado-mountain-lion?utm_source=delivra&utm_medium=email&utm_campaign=todays-headlines-news
2. Fox KA, Breithaupt A, Beer M, et al. Rustrela Virus in Wild Mountain Lion (Puma concolor) with Staggering Disease, Colorado, USA. Emerging Infectious Diseases. 2024;30(8):1664-1667. doi:10.3201/eid3008.240411.