Yellowknife (July 17/06) - An anthrax outbreak among bison in the Slave River Lowlands is believed to be over.

As of July 13, 28 bison carcasses had been found in the isolated north prairie area of the lowlands, about 80 km southeast of Fort Resolution.

A disposal team from the Department of Environment and Natural Resources prepares to burn the anthrax-stricken carcass of dead bison in the Slave River Lowlands. - photo courtesy of the Department of Environment and Natural Resources

"We're not anticipating any new cases," Department of Environment and Natural Resources (ENR) spokesperson Judy McLinton said late last week.

McLinton said, based on the decomposition of the carcasses, all the bison died about two to three weeks ago.

"They all died about the same time."

The area has recently had cooler temperatures and rain, which makes it less conducive for the anthrax spores to come out of the ground, she noted. Anthrax is a naturally occurring disease caused by the bacteria Bacillus anthracis.

Under certain conditions, such as high water followed by hot and dry weather, spores concentrate in low-lying areas.

Bison contract the disease by inhaling contaminated soil while wallowing in dust baths.

A bison usually dies within 72 hours of contracting anthrax and can't travel very far.

The last carcass was discovered July 12, although surveillance flights are still searching the area, McLinton said.

"They're still looking for other ones," she said.

As of last Thursday, 19 carcasses had been burned and ENR teams in protective gear are continuing the disposal work.

All the dead bison have been found in an eight-kilometre radius from where the first two were discovered June 26.

An Alberta laboratory of the Canadian Food Inspection Agency confirmed anthrax was the cause of death on July 10.

"It seems pretty typical," she said, noting 12 bison died from anthrax in 2001 and 1978, 33 in 1971 and 44 in 1964.

The area remains closed to the public, until the disposal of all carcasses is finished.

McLinton said the work is expected to be completed early this week.

Humans can contract anthrax from contact with infected animals or carcasses.

Infections in humans can be fatal, but can be controlled if promptly treated with antibiotics.

The dead bison were originally spotted by an ENR anthrax surveillance flight. Such flights happen every year and will continue this summer until mid-August.