B.C. First Nations launch drug trial to combat mange in declining bighorn sheep population

CBC

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Residents of the South Okanagan in B.C. have noticed an increase in psoroptic mange, a parasitic skin disease, among the area's bighorn sheep.
A decline in their population is prompting a new study.
Research for the study, led by the Okanagan Nation Alliance (ONA), a First Nations tribal council, began in February and will continue until July 2026.
The alliance says big horn sheep are woven into the history of the Syilx people, with their presence reflecting the health of the land and the balance between people and nature. The Syilx are indigenous to the Okanagan, and their territory reaches into the United States.
The Wild Sheep Society of British Columbia is helping fund the research, which also involves a number of provincial and regional biologists. It says B.C. is home to some of the largest and most diverse populations of wild sheep in North America.
Mackenzie Clarke, ONA Wildlife Program lead, says that all bighorns from Penticton down to the United States have the skin disease.
"There's a little mite that eats away at that top surface layer. it causes weeping sores, scabs and build-up of really itchy skin, so the sheep can't stop itching … they have a lot of hair loss," she told CBC's Daybreak South.
Hair loss and hearing loss, because mites build up crust inside of sheep's ears, can have fatal outcomes, she says.
Some sheep die due to exposure during the winter when they lose their hair, and hearing loss makes the sheep vulnerable to predators and vehicles on the road.
Clarke says that researchers believe psoroptic mange here originated from a domestic rabbit farm in B.C.
During a previous trial, genetic testing was done on the sheep, and researchers say they are certain the disease came from a domestic rabbit farm that was in close proximity to the sheep.
She says that no wild rabbits in the area have the disease and that the domestic rabbit farm doesn't exist anymore.
"It can switch between hosts, so that's why we're wanting to kick off this drug trial now, if we can, to try to get a treatment for it, before it does potentially host switch again," she said.
Mange medication trial
Bighorn sheep were captured, and two different drugs are being tested to see which is more effective in mitigating mange and which lasts longer.
Fluralaner and moxidectin are the drugs, sourced from Australia. The Penticton Indian Band, a partner in the project, is holding the sheep.
A previous mange mitigation trial from 2016 that also happened within the Penticton Indian Band was an inspiration for this study, says Clarke. She says that fluralaner was used in the previous mange trial and worked, and that moxidectin is used in the UK on domestic sheep.
She says if the drugs work, all bighorn sheep in the South Okanagan will get it.
Decline in bighorn sheep
Psoroptic mange is limited to the South Okanagan area west of Penticton and was first detected there in 2011.
Clarke says that since then, 60 per cent of bighorn sheep populations have declined. She hopes the study helps rejuvenate those numbers. Lia McKinnon shares those sentiments.
McKinnon is a stewardship biologist with Okanagan Similkameen Stewardship Society, an organization that focuses on wildlife restoration and has lived in the Okanagan for over 30 years.
She told CBC News that the study "is amazing, there are so many threats to the bighorn sheep."
Another threat to the sheep is pneumonia, which Clarke says the bighorn sheep in the South Okanagan also have.
McKinnon remembers 90 per cent of the bighorn population "dying off" during the 90s because of a spike in pneumonia — the study hopes to address that issue as well, she says.
"One really cool thing about the work being done is that it is being done by the Penticton Indian band in conjunction with the Okanagan Nation Alliance, and the province is involved.