Brock team discovers insect in Ontario that can transmit devastating livestock disease

Ontario’s livestock industry was rocked in September 2015 when a farm animal in Chatham-Kent tested positive for the bluetongue virus, a discovery that ultimately cost farmers millions of dollars.

Now, Brock University researchers have confirmed that an insect able to transmit the devastating virus has made its way to southern Ontario.

Graduate student Adam Jewiss-Gaines found hundreds of Culicoides sonorensis, known as the biting midge, when he examined traps in a dozen locations from Niagara to Chatham-Kent.

“This is a species that we didn’t expect to find here,” says Jewiss-Gaines, lead author of the team’s paper, which is published in the Journal of Medical Entomology. “It was mainly located in British Columbia, Alberta and parts of the U.S.”

He said biting midges are tiny and therefore not strong fliers, but wind currents from the U.S. may have brought the insect to the area. Another possibility is they arrived with a shipment of farm materials or livestock, hitching a ride with the animals they feed upon.

The biting midge can carry the bluetongue virus, which causes immense suffering and death, primarily in sheep and deer. Symptoms include fever, swelling of the lips, difficulty swallowing and a swollen, purple-coloured tongue. Some animals bleed at the feet, causing them to walk on their knees.

This is a species that we didn’t expect to find here

The Brock team’s investigation started in 2012, when Jewiss-Gaines found biting midges caught in a trap in Thorold. He and his supervisor, medical entomologist Fiona Hunter, launched a project to see if the insect was present within southern Ontario. Graduate student Larissa Barelli was also involved in the research, lending a hand with molecular work.

In 2013, Jewiss-Gaines discovered Culicoides sonorensis in five traps between Niagara and Sarnia. In 2014, further traps in southwestern Ontario caught more biting midges. Finding the insect in consecutive years concerned researchers, as it was previously thought biting midges could not survive Canadian winters.

Then, in September 2015, the Canadian Food Inspection Agency reported the Chatham-Kent farm animal had tested positive for bluetongue.

“This created chaos in the livestock industry because international exports of live ruminants, and even exports of bull sperm, were immediately halted,” says Hunter. “It cost our livestock producers millions of dollars, I’d estimate.”

Cattle, goats and elk can be infected, but show few symptoms. They act as “reservoirs” that the biting midge can tap into and spread to other livestock.

“There are a lot of livestock farmers here in Ontario,” says Jewiss-Gaines. “Bluetongue could be a real issue if it gets into flocks of sheep because the sheep here aren’t used to it. They don’t have the antibodies; if it gets into those flocks, it could be potentially decimating.”

Getting rid of biting midges is tricky, explains Jewiss-Gaines.

“The larval forms exist in muddy, semi-aquatic environments. If we get a lot of precipitation, they might have a lot of areas to develop in. Biting midges are hard to control. You can’t just go out there and get rid of all the mud.”

Jewiss-Gaines encourages farmers to keep their livestock in barns at dusk and dawn, when the midges are most active, and to put screens on barn windows.

The paper, “First Records of Culicoides sonorensis (Diptera: Ceratopogonidae), a Known Vector of Bluetongue Virus, in Southern Ontario,” can be seen online.

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