[LINK] "Voyageurs' TB thrives among First Nations"

[rfmcdonald]

Emily Chung's extended CBC article in surprising in several ways, documenting (for instance) the long-standing ties between French Canadians--then, as commenters at CBC point out, simply Canadiens--and First Nations, the highly contingent nature of the transmission of pandemic diseases, and the extent to which these pandemics can remain below public attention for decades or even centuries. Parallels with the early pre-1981 spread of HIV seem entirely merited.

Remote First Nations communities in Ontario, Saskatchewan and Alberta share the same dominant strain of the infectious lung disease because they all got it from French Canadian fur traders in the 1700s — a century before any TB epidemics were reported in those communities, says a study published this week in Proceedings of the National Academy of Sciences.

The research shows that tuberculosis spread by a brief historical interaction can stay dormant in a community for 100 years or more before emerging as an epidemic, said Caitlin Pepperell, the Canadian researcher at Stanford University who led the study.

"It points out why it's so difficult to eradicate TB," she added in an interview Wednesday.

[. . .]

During an earlier study, she noticed that DNA fingerprints from remote Ontario and Saskatchewan communities were very similar to each other, "which I thought was odd, because they're very distant populations," she said.

It was also peculiar because TB has thousands of strains across Canada, said David Alexander, a molecular microbiologist with the Ontario Agency for Health Protection and Promotion and assistant professor at the University of Toronto. He was one of 12 Canadian and U.S. researchers who co-authored the study.

In urban areas like Toronto, every infection usually belongs to a different strain, Alexander said: "To have a single strain or a single variant that's so dominant is really unusual."

Pepperell suspected that the Ontario and Saskatchewan communities' location along historical fur trade routes was the common link between them.

With help from researchers in Ontario, Alberta and Quebec, Pepperell analyzed genes from the bacterium that causes tuberculosis, Mycobacterium tuberculosis or M. tb, from the French Canadian population of Quebec and aboriginal populations outside urban areas in Ontario, Manitoba, Saskatchewan and Alberta over the past 20 years. However, the data from Manitoba was too limited to do the type of analysis done for the other provinces. Pepperell then compared the genetic data to trade routes used by the voyageurs.

Only a few thousand French Canadian voyageurs were involved in trading furs with aboriginal populations between 1710 and 1870, resulting in close trade relationships and intermarriages. After that, French Canadians had almost no contact with those distant, isolated aboriginal communities.

In Canada, there are thousands of strains of the infectious lung disease tuberculosis. But one particular strain dominates in remote First Nations communities in Ontario, Saskatchewan and Alberta. In Canada, there are thousands of strains of the infectious lung disease tuberculosis. But one particular strain dominates in remote First Nations communities in Ontario, Saskatchewan and Alberta. (Associated Press)And yet, genetic data in Pepperell's study showed that the French Canadian population of Quebec was the source of the dominant tuberculosis strain found in aboriginal populations along former fur trade routes today. It also showed that the original transmission took place in the 1700s.

Pepperell suggests that tuberculosis became epidemic in Canadian First Nations communities only when living conditions deteriorated sharply from the late 19th century on, as traditional lands were confiscated, children sent to residential schools, and living conditions on reserve became--and remained--Third World.