Chronic Wasting Disease (CWD) is a deadly illness that affects deer in some rural parts of the U.S. and Canada. There isn’t any strong evidence that CWD infects people, but if you hunt or have contact with deer, there are precautions you can take to keep yourself safe regardless.
What is CWD?
Chronic Wasting Disease (CWD) is a fatal brain disease caused by infectious prions (we’ll talk more about those in a moment). It affects cervids, which is the scientific term for the deer family, and includes deer, elk, moose, and reindeer.
CWD was first discovered in the 1960s and is now considered an established wildlife disease across North America. Although there are no known cases of CWD infecting humans, health agencies recommend that people avoid eating meat from animals that test positive for the disease.
Wait, what exactly are prions?
Prions are misfolded versions of normal proteins, which, when they happen in the brain, can cause serious disease. On rare occasions, regular proteins can stop folding in the way they normally do, which causes these tiny proteins to clump together and become prions. They’re unusual in the world of infectious agents because, unlike viruses and bacteria, prions contain no genetic material (no DNA or RNA). They are also incredibly small, even smaller than viruses, which makes them really difficult to spot.
💡Did you know? The term “prion” is a mash-up of the words “Proteinaceous infectious particle.”
So what about prion disease?
Prion diseases are also called “transmissible spongiform encephalopathies” – TSE for short. They are a group of rare and deadly diseases that affect the brain and spinal cord (aka the central nervous system) and can occur in mammals – and they are caused by the misfolding of prions we described above.
Prion disease causes brain damage, which is why common symptoms include involuntary movements, vision problems, difficulty with coordination and balance, and rapidly progressing dementia. It has a long incubation period (this means it can take years between someone getting infected and starting to show symptoms), and unlike many other infections, it does not cause any inflammation, making it even harder to detect. Sadly, prion disease always worsens over time and is always fatal.
💀Prion diseases in animals include:
🐄The most “infamous” prion disease in animals is “mad cow disease” or bovine spongiform encephalopathy (BSE) by its scientific name. You might remember there was an outbreak of mad cow disease in the UK in the 1990s
🐑Scrapie, which occurs in sheep and goats
🦌Chronic Wasting Disease in cervids – deer, elk, moose and wild reindeer
I’m a human – are there prion diseases that might affect me?
Sadly, yes. It is important to remember that these are extremely rare and can’t be transmitted through the air, through touching or casual contact, but human versions of prion disease include:
🫥Kuru – This was discovered in the 1950s in Papua New Guinea and was considered the first human prion disease. When the source was found (ritual cannibalism), and the practice was stopped, the disease went away!
🫥CJD or Creutzfeldt-Jakob Disease – there are three types of this disease:
- “Sporadic”: this is when the misfolding happens spontaneously without a known cause.
- “Hereditary” or familial, which means it has been passed on from a parent.
- “Acquired”, which means a person gets this through being exposed to infected brain or spinal cord tissue.
🫥 vCJD or “variant Creutzfeldt-Jakob disease (vCJD) – This is the human form of mad cow disease and is transmitted from eating meat from an animal with “mad cow disease”. During the mad cow disease outbreak in the UK in the 1990s, prions from infected beef entered the human food chain before the disease was detected. 178 people were infected and died. Worldwide, more than 220 people have been infected with vCJD and have died. As a result, the UK and other countries introduced strict guidelines for screening and control to reduce any risk of this happening again.
And what about the transmission of Chronic Wasting Disease (CWD)?
🙌 Firstly, the good news: so far, there are no reported cases of humans developing prion disease that have been linked to a deer with CWD.
Transmission between animals happens in several ways: saliva, blood, urine, feces, brain matter, and antler velvet are among the main routes. It’s important to know that the number of prions increases as the disease gets worse, so the sicker an animal is, the more prions are around, increasing the risk of transmitting the disease to other animals.
Are there ways I can protect myself?
If you come across a deer, elk, or moose that appears very thin and sickly, or that behaves oddly (e.g., it staggers, shows a lack of awareness, or salivates a lot):
✅ Report the location to your nearest Park Service, Ranger or wildlife agency.
If you are someone who hunts:
❌ Do not shoot, handle, or eat meat from cervids that look sick, are acting strangely, or are found dead (roadkill).
‼️ It is strongly recommended that you have your harvested animal tested for CWD before eating the meat.
‼️ If your animal tests positive for CWD, do not eat the meat and always dispose of it so it can’t pose a risk to others (e.g., double-bag in strong garbage bags and dispose of at a landfill with an approved dead animal disposal area).
✅ Check your state wildlife and public health guidance for testing recommendations and requirements. These may vary by state, but most state wildlife agencies provide information on testing.
If you are also someone who field-dresses (removes the internal organs while still “in the field”):
✅ Wear latex or rubber gloves when you dress the animal or handle the meat, and thoroughly wash your hands after
✅ Minimize the handling of any organs, but particularly the brain and spinal cord tissues.
✅ Thoroughly clean your tools after any harvesting of an animal – the Chronic Wasting Disease Alliance recommends soaking your tools for 5 minutes in a 40% solution of household bleach to inactivate prions
❌ Do not use household knives or other kitchen utensils for field dressing.
You can find more information for hunters here.
The U.S.Geological Survey’s (USGS) National Wildlife Center has a map providing the best available information on CWD locations:
(source: USGS National Wildlife Center)
A word about surveillance
By monitoring which areas have infected deer, wildlife agencies can alert hunters to take extra precautions, recommend testing in high-risk zones, and work to slow the spread of the disease.
Regular surveillance also helps scientists and researchers watch for any changes in how the disease behaves—this is a crucial part of public health that not only keeps tabs on CWD but also keeps people informed and safe.
Bottom line: Although CWD is out there infecting deer, and prion diseases are really scary, there are no reports of transmission of CWD to humans or any human cases, and there are ways you can protect yourself by following some simple strategies.
Stay safe, stay well.
Love,
Those Nerdy Girls
Useful resources:
CDC – About Chronic Wasting Disease
CIDRAP – CWD Frequently Asked Questions
CWD Alliance – Recommendations for hunters
Colorado Parks and Wildlife – Chronic Wasting Disease
Nerd References:
