In recent years, a mysterious symptom complex has occasionally appeared in young black bears in the Tahoe Basin. In the past five weeks, these two serious one-year-old larvae have been found in Northern California and have now appeared.
A sick young man who was euthanized and found to have brain inflammation or encephalitis was found about 15 miles between eastern Humboldt County and the county line across Trinity County in late February and early March.
Monte Merrick, director of the Humboldt Wildlife Care Center, who received the first two bears, said that a third bear was observed in the same area on Wednesday, possibly a sibling. Although it was not captured, it showed similar symptoms.
Officials said these animals are the first known cases of common symptoms outside the Tahoe area, mainly encephalitis, which has been recorded since 201
Experts say that since then, fewer than 20 cases have been inspected from both sides of the state boundary, most of which are from the Tahoe Basin. The Tahoe Basin has a large number of black bears, and there are enough opportunities for people to meet.
But the pace of discovery has increased over the past 1.5 years, partly because “we have been looking for it,” said Brandon Munch, a senior wildlife veterinarian at the Wildlife Investigation Laboratory of the California Department of Wildlife. Since 2016
“Once you start looking, start looking,” Munch said. “To make a long story short, we really don’t have a benchmark to say how common this is.”
Most sick bears are about half or one-third the size of their one-year-olds-although none are smaller than those passing through Humboldt County. Many people have strange gait or head tilt, tremors or other neurological symptoms, as well as sluggishness, unresponsive behavior, or fearless “dog-like” behavior.
Researchers increasingly concerned about this issue have discovered five previously unknown and unidentifiable viruses in tissue samples from some of these bears and other bears obtained for various reasons. Two of the five viruses are common.
Meng Ke said that the type of inflammation suggests a virus, although scientists are still a long way from linking symptoms to any particular source, and other causes have not been ruled out. It is not yet known whether these bears have suppressed their immune system for other reasons and then died of viruses or diseases that would not otherwise be fatal, or whether their situation is only now emerging due to increased human interaction with wildlife.
Sanchez of the Nevada Department of Wildlife said: “This may be related to urbanization, but at the same time, it may have happened in the wild, and we just didn’t see them.”
Denise Upton, director of animal care at the South Lake Tahoe Wildlife Conservation Organization in Lake Tahoe, said that animals with this syndrome are still rare, but it is sometimes difficult to tell because humans are attracted to discarding trash and other temptations. Animals even feed the bears directly and become accustomed to people carelessly.
During this period, her organization increasingly treated and released severely overweight cubs. These cubs were still young enough to be with their mothers, but for some reason they did not. Upton said those animals, including the four at the beginning of last year, have apparently spent the entire winter alone, but have not shown neurological defects or other major problems.
“We don’t know what will happen in the forest,” Upton said. But cubs who see a person starving to death “will not show fear, because hunger will overwhelm their fear.”
“My question is’what happened to all their mothers?'” she said.
Merrick said the two bears taken by the Humboldt County Wildlife Center roamed the areas near Willow Creek and Salyer, which are about 260 miles north of Santa Rosa.
Munch said that in the case of acute skin diseases, their weight is approximately one-quarter and one-eighth of their age (approximately one year old) expected weight.
Merrick said the female was arrested on February 27, weighing only 10 pounds (this cub usually reaches this size before weaning), and was originally taken by the Sonoma County Wildlife Rescue. Accepting rehabilitation, the state is one of three wildlife rehabilitation centers authorized by the state. Then Munch looked at her picture.
“I said,’Eeeeeee. I know what it is, and the prognosis is very poor,” he recalled.
Munch said that although the observation of her before she was put down did not reveal any external signs of neurological disease, the animal had been transferred to a research laboratory and was later found to have mild encephalitis.