From this press release from the USGS website:
Certain lichens can break down the infectious proteins responsible for chronic wasting disease (CWD), a troubling neurological disease fatal to wild deer and elk and spreading throughout the United States and Canada, according to U.S. Geological Survey research published today in the journal PLoS ONE. Like other "prion" diseases, CWD is caused by unusual, infectious proteins called prions. One of the best-known of these diseases is "mad cow" disease, a cattle disease that has infected humans. However, there is no evidence that CWD has infected humans. Disease-causing prions, responsible for some incurable neurological diseases of people and other diseases in animals, are notoriously difficult to decontaminate or kill. Prions are not killed by most detergents, cooking, freezing or by autoclaving, a method used to sterilize medical instruments.
"When prions are released into the environment by infected sheep or deer, they can stay infectious for many years, even decades," said Christopher Johnson, Ph.D., a scientist at the USGS National Wildlife Health Center and the lead author of the study. "To help limit the spread of these diseases in animals, we need to be able to remove prions from the environment." The researchers found that lichens have great potential for safely reducing the number of prions because some lichen species contain a protease enzyme (a naturally produced chemical) capable of significantly breaking down prions in the lab.