What Is Chronic Wasting Disease? Could Mysterious 'Zombie Deer' Illness Kill People?

It may take up to 16 months for a deer to show signs that it's been infected with chronic wasting disease, a deadly prion-based illness that makes the animals act like "zombies." While there hasn't been a documented case of a human getting the disease, new research suggests it has the potential to evolve and jump to humans who interact with deer and eat their meat.

Researchers at the Canadian Food Inspection Agency studied macaques, monkeys that are known to be susceptible to the same prion diseases as humans. They fed the macaques venison, or deer meat, infected with chronic wasting disease. After three years of eating a total of 5 kilograms of infected venison each, three out of the five macaques were found to be infected with CWD. The human equivalent would be eating one 7-ounce steak per month.

"Macaques are susceptible to human prions, and that's why they're a good model for a species barrier jump," Mark Zabel of Colorado State University's Prion Research Center told Newsweek. "We know that they will develop a prion disease from human prions." Zabel was not involved in the macaque study.

Prions are contagious, misfolded proteins that cause other proteins in the brain to behave abnormally and misfold. The agents are also very versatile, as they have historically adapted to their respective hosts. Sheep with scrapie transferred their disease to cattle, where it became "mad cow disease," and people eating the infected beef became infected with variant Creutzfeldt-Jakob disease.

The fear that people could become infected with chronic wasting disease led the Canadian government to issue a warning to those eating deer meat. You can test meat for CWD, and once it's infected, there's nothing to do but destroy it.

"Prions are very stable, and they survive the temperatures that would be involved in cooking the meat," Zabel said. "Freezing does absolutely nothing."

This trans-species infection scare harkens back to the 1980s and '90s, when people in the U.K. who ate beef from cattle infected with a prion disease also found themselves infected with a prion disease. However, deer meat consumption in the U.S. is primarily localized to hunters and their friends and family. If an infected deer is slain and then shared among a small group of people, their risk could be high, since they're likely to eat more of the infected animal.

"Consider a hunter who harvests an infected deer," Zabel explained. "He and a few of his friends and family will eat that meat. That means that the dose of prions that they might receive might be hundreds of times higher than those unfortunate individuals that ate the contaminated beef in the U.K."

Symptoms include strange behavior, drooling, a vacant gaze and difficulty walking and eating, which can lead to starvation and death.