Newly discovered deadly disease affecting cats of all sizes found in the U.S.

As of August, Colorado Parks and Wildlife isn’t receiving an increase in reports of sick or dead mountain lions, nor are they seeing an increase in dead collared mountain lions. The state will continue its existing surveillance programs, which could turn up sick cougars for more testing, if they exist.

Elizabeth Buckles, a wildlife pathologist at Cornell University who wasn’t involved in the diagnosis, notes that „almost anything“ can happen to wildlife dealing with a new disease. „Do [the animals] have some level of immunity to it?“ she said. „Or is it all new? If it’s all new, like we saw with white nose syndrome or we’re seeing with avian influenza virus, it’s going to take a while for immunity to develop.“ How a population responds to a new disease can be influenced by a variety of factors, including how often animals reproduce, and if they gather in groups or travel long distances to new areas.

Now that the virus is officially confirmed in the U.S., Fox hopes to work with veterinarians who’ve saved samples from undiagnosable past cases to retroactively test the domestic cat population. This could help identify if the disease already exists in our pets. Another big question that Fox and her German colleagues want to tackle is how the disease spreads.

How does staggering disease spread?

The same 2023 study that found the rustrela virus link also identified rodents, including wood mice and yellow-necked field mice, as the virus’ European hosts. Any number of small mammals, including deer mice, squirrels or chipmunks, could be carrying the disease in Colorado with no side effects to their health — similar to the way mice transmit hantavirus but aren’t sickened by it. Fox would like to trap these creatures and test their brain and spinal matter to find out more.

Eating mice is the most obvious way cats (and cougars) could pick up the virus. But the exact transmission mechanics, like how the virus might go from the stomach to the brain, are unclear. Researchers think cougars and other larger mammals with the disease are „dead end hosts,“ meaning they don’t further spread the disease. The virus from the Colorado cougar is genetically different from several European strains of the virus, suggesting it may be a distinct version of the virus that’s been in the U.S. for a while, undetected — not something that was recently introduced to the continent. 

In conclusion, the investigation into the disease affecting mountain lions in Colorado is ongoing, with researchers and wildlife experts working to understand the transmission and impact of the virus on both wildlife and domestic animals. By studying the behavior and biology of the virus, scientists hope to develop strategies to mitigate its spread and protect vulnerable populations. As more information becomes available, it will be crucial for conservation efforts to adapt and respond to this emerging threat to wildlife health.