Lindsay Renda and Riley Strang are second year Recreation, Fish and Wildlife students at Castlegar’s Selkirk College. Photo: Submitted

Lindsay Renda and Riley Strang are second year Recreation, Fish and Wildlife students at Castlegar’s Selkirk College. Photo: Submitted

ECOLOGICAL COMMENT: Midge-borne disease devastates bighorn sheep population in Grand Forks

Hot weather and drought have created ideal temperatures for the transmission of the Bluetongue virus

Submitted by Riley Strang and Lindsay Renda

Hot weather and drought conditions in interior British Columbia have created ideal temperatures for the transmission of the Bluetongue virus. Bluetongue is usually fatal in bighorn sheep and can also affect other ruminants (large, hoofed mammals) says Dr. Caelet Thacker, B.C.s provincial wildlife veterinarian.

Bighorn sheep are a blue-listed species in BC which means they are a species that is not immediately threatened but they are of concern due to their sensitivity to human activity and natural events. This herd was one of the few in the province that was doing extremely well prior to the event, says Bear Brandrow, a local hunting guide in Grand Forks.

Bluetongue is carried by an insect, a biting midge. In bighorn sheep common symptoms of bluetongue virus are swollen lips and a high fever. In a 10-day span the population of bighorn sheep in Grand Forks was reduced drastically and unfortunately there was nothing that could be done for the sheep that were already infected. Lab tests confirmed that the sheep in Grand Forks died from this disease in summer 2021.

Morbidity for bighorn sheep can be up to 100 per cent. The results of infection can be devastating to any herd but even more so to one as small and isolated like the one in Grand Forks.

Although they carry and transmit diseases that are fatal among certain animal populations, midges play an important role in our fragile ecosystem. Midges are an important food source for aquatic insects, fish, amphibians, birds and bats. The larvae clean the aquatic environment by consuming decomposed organic matter and recycling it. These tiny insects thrive in virtually every freshwater habitat. There are more than 4,000 species of midges globally and more than 600 of these occur in North America. Midges are found on every continent but Antarctica. In Canada alone, there are over one thousand named species of midges. They are found across the country and live in a variety of habitats.

They are also great indicators of pollution. The presence of midges in tidal pools, indicates healthy oxygen levels in water. The absence of midges can indicate pollution or poor water quality. In sewage treatment plants, water authorities use midge counts to help monitor contamination levels. Some midges are predators that feed on bacteria, algae, water fleas and other larvae, organisms that can contaminate water supplies. Additionally, midges are natural pollinators, which is beneficial to agriculture.

While midges have an impact on wildlife, they do not transmit diseases to humans. Hopefully there can be a solution to protecting sheep and deer from the midge-borne disease, bluetongue, without destroying an abundant food source to aquatic animals and other wildlife.

Riley Strang and Lindsay Renda are second year Recreation, Fish and Wildlife students at Castlegar’s Selkirk College.

Environment