Near Grand Forks, B.C., a disease outbreak is killing wild bighorn sheep and white-tailed deer, and the death toll is projected to rise. According to members of the Wild Sheep Society, the bighorn sheep herd in this portion of the West Kootenay region is estimated to number roughly 230 animals, with at least 20 of them dead so far.
The disease responsible is bluetongue, which is spread by the Culicoides biting fly. After a number of animals collared for a conservation study stopped moving, Kyle Stelter, president of the Wild Sheep Society of British Columbia, said members realized something was wrong.
Other than a predation event, Stetler thinks it’s unusual to have something like this happen in the middle of summer. According to Dr. Caeley Thacker, B.C.’s provincial wildlife veterinarian, bluetongue is usually fatal in bighorn sheep, but it can also infect other ruminants like white-tailed deer.
Although it has afflicted herds south of the border, it is not a particularly frequent disease in British Columbia. She claims that the flies arrive as a result of a shift in environmental conditions or wind. According to Thacker, once an animal is afflicted, the sickness progresses and the animal would most certainly die.
The flies can only be stopped by a frost, which disrupts their life cycle and kills them. In British Columbia, bighorn sheep are a blue-listed species. This indicates they aren’t in danger right now, but they are a species “of concern” because they are especially vulnerable to human actions or natural catastrophes.
While there isn’t much that can be done for the afflicted bighorn sheep save wait for the flies to die off in the frost, Stelter hopes that more can be done to maintain the habitat for the survivors.