Anthrax Suspected in the Death of Canada's Bison

Jul 12, 2012 | Robyn Correll Carlyle |

Canadian news organizations reported Monday that another 23 bison carcasses were found in Canada’s Northwest Territories.

Last week the Northwest Territories Department of Environmental and National Resources (ENR) announced 128 bison carcasses were found near Mills Lake, an area northwest of Fort Providence, during a routine anthrax surveillance flight. That number jumped to over 150 when more carcasses were found near Caen Lake.  

Officials at the ENR said they believed the deaths were caused by anthrax.

"A field test on a couple of carcasses did turn out positive," said Judy McLinton, spokeswoman for the ENR. "Given the number of carcasses and the chance when they looked at them that it was probably or potentially anthrax, we activated our emergency response plan."

Samples from the animals were sent to the Canadian Food Inspection Agency to confirm the presence of anthrax. Lab results are expected back this week.

Anthrax is caused by the bacterium Bacillus anthracis, which survives by releasing spores that can remain in soil for years.  When wet periods are followed by hot, dry spells, the spores concentrate along the ground surface. Animals, such as bison, contract the disease by inhaling the spores when they roll in the mud to keep cool. Anthrax is not typically spread from animal to animal.

Humans are infected by coming into contact with or inhaling anthrax spores, sometimes found on animal products like wool, or by consuming undercooked meat of an infected animal.

Symptoms usually appear in humans within seven days of infection and range depending on how the bacterium was contracted.  The most common form of infection occurs when spores come in contact with a break in the skin, causing sores and dark ulcers. When humans eat the infected meat of an animal, severe gastrointestinal symptoms can appear, such as nausea and bloody diarrhea.

Pulmonary anthrax, caused by the inhalation of spores, is the rarest and most severe form of the disease. Initial symptoms mimic that of a cold or the flu, but can quickly escalate into severe respiratory problems and sometimes shock.

While anthrax can be fatal, it can be controlled with prompt antibiotic treatment.

The ENR reported warning people in the area not to come in contact with the carcasses. Protocol dictates that the deceased animals be burned, but McLinton said this process would take weeks. In the meantime, the carcasses will be treated with formaldehyde and shielded with canvas until they can be properly disposed of. 

An ENR command team is stationed in Fort Providence to deal with the potential outbreak, and routine aerial surveillance will continue through August.  

According to McLinton, the last large outbreak in the area took place in 1992, when 172 animals died from anthrax. Another outbreak in 2009 killed nine bison.

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