Idaho just received its second domestic case of Chronic Wasting Disease: What is it and what does that mean?

Chronic Wasting Disease, or CWD, is a deadly and incurable neurological illness. Idaho just received its second confirmed case in domestic elk.

What is Chronic Wasting Disease

CWD is a prion disease, a type of illness not caused by viruses or bacteria, but instead by misfolded proteins called prions. When enough prions enter the body, they can create a chain reaction of damaging normal proteins in the body which leads to cell destruction and neurological damage, and inevitably, death of the organism.

Prion diseases are currently incurable and the only known ones occur in mammals. CWD affects animals in the deer family (cervids) such as but not limited to: moose, caribou, mule deer, reindeer, red deer, and elk. CWD was first found in Colorado in 1967, but through the years has been detected across the globe.

“It’s in Asia, Europe and North America,” said Professor Mark Zabel with the Prion Research Center at Colorado State University

How is it spread?

Zabel said that the disease can be transferred directly–for instance from a sick moose to a healthy moose–as well as transferred indirectly due to the prions’ infectious properties,

“…unlike many most other pathogens, it’s very stable in the environment. So it can remain infectious in the environment, in soil and landscapes. For years to decades.”

Prions get into the environment (soil, water, plants, etc) through excretion by infected animals, such as through their urine, feces, saliva, and decomposing bodies. Then, due to the prion’s very stable protein structure, they’re able to stay infectious for up to 20 years. This means other animals can pass through the environment, and pick up the prions laid decades past, and still get infected.

CWD is difficult to detect because animals may be infected for long periods of time without showing signs due to the disease’s incubation period. On average, the time between initial infection and first signs of it is 18 to 24 months long.

Concerns of the Disease

Not only is CWD an ecological concern due to the difficulty of combating it, but it is also a severe economic issue regarding wildlife and agriculture governmental agencies. The most recent data shows the government as spent $280 million dollars on CWD from 2000-2021. A majority amount of that was spent by the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.

Idaho first saw CWD in wild mule deer in 2021. Within the past two months, there have been two confirmed cases of domestic elks that were from different elk farms, meaning, they couldn’t have infected one another. In Idaho’s 2021-2022 fiscal year, wildlife agencies spent close to $225,000 trying to combat CWD.

Zabel told me his main concern as a scientist is “…this disease could spread to humans, you know. So it has some zoonotic potential, similar to another prion disease that people might be aware of called bovine spongiform encephalopathy or BSE. Probably more commonly known as mad cow disease.”

When someone eats beef contaminated with Mad Cow disease, a variant of the prion disease from the cow can be made to infect a human. For now, CWD does not have the ability to change to infect humans, but since it is a prion disease, it is possible that it could develop one.

What you can do to stay safe and help

Zabel encourages hunters to follow state practices to reduce the possible spread of CWD and to test their harvest before eating. There’s no evidence yet that CWD can transfer from cervid to human but Zabel told me,

“I would definitely not want to be the reference case. I don’t want to be patient zero.”

This past year, Idaho Fish and Game released hunting guidelines to reduce the spread of CWD . The agency also offers free testing kits for hunters to help track the disease by sending in samples of their game.