Yellowstone zombie killer

Deer fall prey to deadly brain disease, raising ecological fears

- Todd Wilkinson

When the mule deer buck died in October, it perished in a place most humans would W consider the middle of nowhere, miles from the nearest road. But its last breaths were not taken in an isolated corner of American geography. It succumbed to a long-dreaded disease in the backcountry of Yellowstone National Park, northwest Wyoming - the first confirmed case of chronic wasting disease (CWD) in the country's most famous nature reserve.

For years, CWD, caused by prions- abnormal, transmissible pathogenic agents - has been spreading stealthily across North America, with concerns voiced primarily by hunters after spotting deer behaving strangely.

The prions cause changes in the hosts' brains and nervous systems, leaving animals drooling, lethargic, emaciated, stumbling and with a telltale "blank stare" that led some to call it "zombie deer disease". It spreads through the cervid family: deer, elk, moose, caribou and when the mule deer buck died in October, it perished in a place most humans would reindeer. It is fatal, with no known treatments or vaccines.

Its discovery in Yellowstone, whose ecosystem supports the greatest and most diverse array of large wild mammals in the continental US, represents an important public wake-up call, says Dr Thomas Roffe, a vet and former chief of animal health for the fish and wildlife service, a US federal agency.

"This case puts CWD on the radar of widespread attention in ways it wasn't before - and that's, ironically, a good thing," he said. "It's a disease that has huge ecological implications."

Roffe had been predicting CWD would reach Yellowstone for decades, warning that both the federal government and the state of Wyoming needed to take aggressive measures to help slow its spread. Those warnings went largely unheeded, he said, and now the consequence will play out before the park's millions of annual visitors.