First Nations Launch Comparative Drug Trial to Combat Psoroptic Mange in Declining Bighorn Sheep Population
Key Insights
The Okanagan Nation Alliance (search) is leading a drug trial testing fluralaner and moxidectin to treat psoroptic mange (search) in bighorn sheep, with research running from February 2025 to July 2026.
Psoroptic mange (search) has caused a 60% decline in bighorn sheep populations in South Okanagan since 2011, with the parasitic disease causing fatal hair loss and hearing impairment.
Researchers traced the mange outbreak to a domestic rabbit farm through genetic testing, highlighting the risk of cross-species transmission.
The Okanagan Nation Alliance (search) (ONA) has launched a comprehensive drug trial to combat psoroptic mange (search), a devastating parasitic skin disease that has decimated bighorn sheep populations in southeastern British Columbia. The research, which began in February 2025 and will continue until July 2026, represents a critical intervention to address a 60% population decline since the disease was first detected in 2011.
Comparative Drug Testing Approach
The trial is testing two antiparasitic drugs—fluralaner and moxidectin, both sourced from Australia—to determine which is more effective in mitigating mange and provides longer-lasting protection. Captured bighorn sheep are being held by the Penticton Indian Band (search), a key partner in the research initiative.
"Fluralaner was used in the previous mange trial and worked, and moxidectin is used in the UK on domestic sheep," explained Mackenzie Clarke, ONA Wildlife Program lead. The current study builds on successful 2016 research conducted within the Penticton Indian Band (search) that demonstrated fluralaner's efficacy against the parasitic infection.
Disease Pathology and Impact
Psoroptic mange (search) is caused by microscopic mites that create severe clinical manifestations in affected animals. "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," Clarke told CBC's Daybreak South.
The disease progression leads to potentially fatal complications. Hair loss leaves sheep vulnerable to exposure during winter months, while mites building up crust inside sheep's ears causes hearing loss, making animals susceptible to predators and vehicle strikes. All bighorn sheep from Penticton down to the United States border are currently affected by the condition.
Zoonotic Origin and Transmission Risk
Genetic testing conducted during previous research definitively traced the mange outbreak to a domestic rabbit farm that was previously located in close proximity to the sheep population. Notably, no wild rabbits in the area carry the disease, and the original rabbit farm no longer exists.
"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," Clarke emphasized, highlighting the urgency of intervention to prevent further cross-species transmission.
Population Decline and Conservation Significance
The mange outbreak is geographically limited to the South Okanagan area west of Penticton, but its impact has been severe. The 60% population decline since 2011 represents a significant conservation crisis for a species already facing multiple threats, including pneumonia (search), which also affects the regional bighorn sheep population.
Lia McKinnon, a stewardship biologist with Okanagan Similkameen Stewardship Society (search) who has lived in the Okanagan for over 30 years, recalled that 90% of the bighorn population died during the 1990s due to a pneumonia (search) outbreak. The current research aims to address both mange and pneumonia threats simultaneously.
Collaborative Research Framework
The study represents a unique collaboration between Indigenous leadership, provincial authorities, and conservation organizations. The Wild Sheep Society of British Columbia (search) is providing funding support, while provincial and regional biologists are contributing expertise to the research effort.
"One really cool thing about the work being done is that it is being done by the Penticton Indian band (search) in conjunction with the Okanagan Nation Alliance (search), and the province is involved," McKinnon noted. "It is really nice having that Indigenous component because the big horn sheep are, of course, super important to our local First Nations population."
For the Syilx people, Indigenous to the Okanagan region with territory extending into the United States, bighorn sheep hold deep cultural significance as indicators of land health and the balance between people and nature.
Treatment Implementation Strategy
If the comparative trial demonstrates efficacy, researchers plan to implement treatment across all bighorn sheep in the South Okanagan region. This population-wide intervention approach reflects the comprehensive strategy needed to address the widespread nature of the mange outbreak and prevent further population decline.
The research timeline extends through July 2026, allowing for thorough evaluation of both drugs' effectiveness and duration of protection, critical factors for determining the optimal treatment protocol for this vulnerable wildlife population.