Chris Pecora

Pestilence, Again

Another normal disaster.

By Kevin Van Tighem

Sometime in  2019 a tiny little virus called COVID-19 discovered a new host species and began to multiply. That would have been merely an interesting phenomenon were it not for the fact that we are the new host. Human immune systems weren’t ready for that little coronavirus, and with so many of us living crowded, interconnected lives around the globe, a pandemic resulted.

The rest is history. Or will be, once the dust settles.

But this is actually nothing new. It’s just that the remarkable advances our species made in the 20th century, both in public health practice and the science of medicine, means we’ve forgotten what pestilence is like. Even the oldest of us have only the faintest of memories of outbreaks of scarlet fever, mumps and other such diseases.

No surprise that we thought we were exempt. But we aren’t; we’re just out of practice. Disease outbreaks are part of nature, and so are we.

We don’t need to look too far back down the trail to start seeing past epidemics. It’s hard to be objective about our own situation, so it might be better to look at other species.

When fur trader David Thompson crossed the Rockies into the upper Columbia River valley in 1807, he and his men nearly starved. There was plenty of habitat but no big game. Several years later James Hector, naturalist with the Palliser expedition, heard from the Stoney people about a mysterious plague that had swept through the Rockies, killing most of the large ungulates. Whatever caused that plague remains unknown, but it likely originated in Europe and was transferred here in domestic livestock. North America’s deer, elk, moose and caribou hadn’t built up immunity to tuberculosis and other domestic animal diseases. Those diseases would have migrated across the continent easily, arriving in the Rockies well before the people who first brought them to the far Atlantic shore.

Eventually Europeans got here too. It didn’t take long before bighorn sheep—which had been isolated from foreign relatives until settlers brought domestic sheep and goats—started dying off as well. At least three times in Alberta’s history, plagues of pneumonia-causing pathogens have almost wiped out our wild bighorn herds. That’s why, in the late twentieth century, the Alberta government declared the forest reserves along the Eastern Slopes of the Rockies out of bounds for domestic sheep. That physical isolation worked; our bighorn populations are thriving again now that they no longer have any risk of touching noses with the wrong animal.

The remarkable advances in health and science in the 20th century made us forget what pestilence is like.

A recent example of a wildlife epidemic has an eerie parallel to our own COVID-19 in that it arose when a pathogen jumped from one species to another. Chronic wasting disease (CWD) first appeared in a Colorado research herd of elk and mule deer in 1967. The facility had previously held domestic sheep. CWD appears to be a variant of scrapie, a brain-wasting disease found in sheep and caused by a rogue protein that attacks the nervous system. When that disease mutated and jumped into deer and elk, it became CWD. Like mad cow disease, to which it is also closely related, it has the potential to be lethal to humans who eat the meat or use antler velvet from infected animals. So far there’s no evidence of that—fortunately, because CWD has now spread across the continent. In eastern Alberta it’s now an epidemic, spreading inexorably west towards the foothills and mountain national parks.

Epidemics are often triggered by a new pathogen finding hosts where endemic populations haven’t experienced it before. It spreads through the group, killing the most vulnerable and sparing those fortunate enough to have strong immune systems or the right gene combinations to resist it. The diseases sometimes miss parts of the population because of isolation or because local conditions don’t favour the microbe in question. The survivors reproduce, the group builds resistance and eventually the outbreak ends. The disease doesn’t necessarily go away, but the species it attacks ceases to be quite so vulnerable. What doesn’t kill you makes you stronger.

Where plagues are concerned, we’ve had plenty. Smallpox, tuberculosis and other pathogens to which Europeans had built up varying levels of immunity were utterly unknown to the Indigenous peoples of North America. Entire Indigenous communities were wiped out by the new diseases, often before their members had even seen their first European. An unfamiliar microbe can be deadly.

Even so, elk, deer, moose and bighorn sheep populations are thriving today. Smallpox and tuberculosis have been mostly relegated to history. CWD hasn’t run its course yet, but science is running to intercept it. Devastating at the time, epidemics pass, and usually nature comes out stronger than before. And we continue the journey together, because that’s how nature works. 

Kevin Van Tighem’s latest book, Our Place: Changing the Nature of Alberta, was released in spring 2017 by RMB.


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