Levin: Learning About CWD

Oct 2, 2018

Until recently, I could neither pronounce nor spell the word prion, an altered cellular protein that triggers a suite of infectious diseases, mostly fatal, in the brain and central nervous system of mammals, including humans.

They cause neighboring normal proteins to fold and attach to abnormal proteins, thus forming long chains, or polymers, an inter-cellular epidemic, like contagious conga lines.

Many prion diseases confine themselves to one particular group of mammals - like Scrapie, which affects sheep and goats. Others, like bovine spongiform encephalopathy, often called Mad Cow disease, can jump hosts and affect us if we eat tainted meat.

Chronic Wasting Disease, or CWD for short, affects deer, elk, moose, and reindeer - producing lesions in the brain, triggering disorientation, emaciation, and certain death. It’s now found in twenty-five states and four Canadian provinces – including a herd of captive deer in Quebec, just one hundred miles from the Vermont border.

Walt Cottrell, a Newbury veterinarian and wildlife biologist, says infected prions are durable and nearly indestructible. They require heating at eleven hundred degrees Fahrenheit for twelve hours to destroy every last one and are shed and spread through feces, urine, and saliva. It takes eleven months before an infected deer will exhibit symptoms, and prions can remain viable on the ground for up to sixteen years and available to hungry plants, which pass them on to browsing deer.

CWD has an incubation period of up to five years, and cannot be diagnosed in a live animal. So there’s no way to tell if a deer has CWD until it’s dead. Bringing the meat and body parts of an infected deer from elsewhere into Vermont is almost guaranteed to spread CWD. And hunters are now advised against using urine-based scents, since Cottrell says “there’s no way of knowing if the donor animal was infected.”

He adds that another way to slow down the spread of CWD is to “target young, antlerless males during the hunting season” since they disperse up to one hundred miles from their birthplace.

Surachai Supattapone, professor of biochemistry at Dartmouth’s Geisel School of Medicine, who specialized in prion diseases, adds “We only know a fraction of what there is to know about prions. We’re always catching up.”