Mysterious brain disease makes bears friendly, then kills them

An unknown neurological disease is smelly and often kills young black bears in California and Nevada. The disease also appears to make bears not afraid of people. While the condition does not appear to seriously harm the bear population as a whole, scientists and wildlife officials are still trying to understand its cause.

According to the California Department of Fisheries and Wildlife, the first reports of the condition date back to 2014, when Nevada officials caught wind of sick bears near Lake Tahoe. There have been sporadic reports since, but in the past 12 months alone, at least four cases have been documented in California.

Symptoms of the disease include lethargy, low weight, head tremors and a slight tilt of the head, as well as a sense of fearlessness around humans that wildlife officials have described as “dog-like.” In one video-documented case in 2019, a cub later found out it had the condition approach a snowboarder without hesitation, seeming to snuggle up next to him. In another report from last fall, a young bear that had been fed by people climbed into an open car trunk without incentive.

Upon closer examination, it was discovered that these bears and others had encephalitis or swelling of the brain. Unfortunately, most bears with this disease have died or been euthanized due to deteriorating health, and some that have survived are unable to return to the wild.

“Anytime a wild animal comes into our care, the best possible outcome is a release back into the wild,” said Brandon Munk, CDFW veterinarian. declaration Last week. “It’s just not possible for these bears with neurological conditions. At this point, we don’t know what causes encephalitis, so we don’t know what, if any, health risks these bears might pose to other animals.

Encephalitis can be caused by many different things, including viral infections. But although scientists have found five previously undocumented virus species in these bears, it is not yet clear whether any of them are linked to the disease. It is also not known whether this condition or its cause could also pose a danger to humans or other animals.

Despite these tragic cases, the black bear population in the areas where these cases were found still appear to be healthy. But for now, the mystery remains unsolved. Officials Carry on to warn that people should not encourage bears to hang around, however friendly they may appear. This is mainly for the benefit of bears, as these encounters are often more dangerous for them than for us.