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Bison killed by anthrax: field test
128 carcasses found 30 km northwest of Fort Providence

Roxanna Thompson
Northern News Services
Published Saturday, July 7, 2012

DEH GAH GOT'IE KOE/FORT PROVIDENCE
Anthrax is the suspected cause for the deaths of a large number of bison in the Mills Lake area.

NNSL photo/graphic

Bison that die from anthrax typically lie on their side in a sawhorse position and are severely bloated. Anthrax is the suspected cause of the death of 128 bison found in an area near Mills Lake, 30 km northwest of Fort Providence. - photo courtesy of the Department of Environment and Natural Resources

On July 3, 128 bison carcasses were found within approximately five square kilometers during an anthrax surveillance flight in the Mackenzie Bison Range.

Field tests were positive for anthrax, said Judy McLinton, the manager of public affairs and communications for the Department of Environment and Natural Resources.

Further samples have been sent to the Canadian Food Inspection Agency lab in Lethbridge, Alta., for testing. While the tests are being done, the department is treating this as a potential anthrax outbreak, said McLinton.

The department has activated its anthrax emergency response plan and stationed an incident command team in Fort Providence. The team includes a trained burn crew.

The crew will be treating each of the carcasses with a chemical sterilent, covering them with tarps to keep scavengers away and then burning each of the carcasses in place using coal and locally sourced wood.

"They found this is the best way to do it," McLinton said.

The process could take up to six weeks, she said.

The location where the carcasses were found is only accessible by boat at this time of the year. There are cabins in the area and the department is closing the area to the public until the carcasses are dealt with, said McLinton.

"It's for public health and safety reasons," she said.

Anthrax is a disease cause by the bacterial bacillus anthracis. Once introduced to an area, anthrax spores can remain viable in the soil for many years. Anthrax outbreaks have occurred in the Mackenzie Bison Range before. In 1993, 172 animals were killed and in 2010 nine were found dead.

There are approximately 2,000 bison in the range.

Anthrax outbreaks have also taken place in the Slave River Lowlands and Wood Buffalo National Park in the territory.

The prevailing scientific explanation for anthrax outbreaks in bison is that during a wet spring followed by hot, dry weather, anthrax spores become concentrated in low-lying areas, said John Nishi, a wildlife and landscape biologist who's dealt with outbreaks in the Slave River Lowlands.

Bison come into the area to wallow and when they kick up the dust they are exposed to the spores by inhaling them or eating them while grazing. The anthrax activates inside the bison, replicates itself and then kills the animal through a combination of lethal and toxic factors. The increased number of spores then become dormant again.

The NWT's anthrax emergency response plan is designed to minimize contamination, said Nishi. Burning the carcasses destroys the spores in the animal and the nearby soil. If nothing is done, the concentration of anthrax in an outbreak area will increase.

Completely eliminating anthrax in the territory would be very difficult, Nishi said.

"The challenge is you are dealing with wild bison in a very large landscape," he said.

A diseased bison may appear indifferent to people, have frothy discharge from the nostrils and swelling in various part of the body.

Infected bison normally die within 72 hours.

Humans can contract anthrax from infected animals or carcasses, usually when spores get through cuts or other breaks in their skin. Anthrax infections can be fatal but can be controlled if promptly treated with antibiotics.

In the North the people at greatest risk of becoming infected with anthrax would be those handling the infected carcasses, which is why proper techniques and safety equipment are used, said Nishi.

"For the average person in the NWT, the risk is remote," he said.

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