Mad Elk Dirt

Hunters in many states have been warned not to eat deer or elk meat, since it can be contaminated with chronic wasting disease (CWD), a version of Mad Cow Disease, which can be transferred to humans who eat the meat. Mad Cow was spread by farmers grinding up cow bones and feeding them to cattle, but how does CWD spread in wild animals? The answer may be that prions stay alive in the dirt.

Prions are the infectious proteins that spread the disease and researchers have found that they’re more likely to live some types of soil than in others, which may be why some areas of the country are affected, while others aren’t. CWD was first detected in deer and elk in Colorado and Wyoming in the 1980s, and in Wisconsin in 2002.

“The route by which CWD is transmitted from animal to animal is not understood,” says environmental chemist Joel Pedersen. “Strong circumstantial evidence suggests an environmental reservoir exists. Soil is a candidate because grazing animals ingest it both inadvertently, as part of feeding, and on purpose, as part of certain deer behaviors.”

Sand and clay are both commonly found in soil, but soil with a lot of clay is more likely to harbor prions. In sandy soil, they either wash away or travel deep into the ground, but in clay, they stay on the surface. Pedersen plans to test various types of soils. He says, “What we’ll be getting at is if prions are more likely to persist in some environments.”

Bigfoot has survived, so maybe our elk and deer will make it too.

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