Like humans, animals risk developing many diseases, ranging from mild to fatal ones. Deer aren’t an exception, unfortunately. Chronic Wasting Disease is one of the most disastrous illnesses deer can get, and it’s always fatal. Infected animals show a wide range of symptoms and are in great pain. Keep reading to learn what symptoms they show, whether the disease can be spread to humans and if there’s a human version of CWD.
What Is Chronic Wasting Disease?
Chronic wasting disease is also called zombie deer disease. It’s an illness that affects deer only, and it’s a transmissible spongiform encephalopathy. This means CWD is a disease that affects the deer’s brain and nervous system.
Most hypotheses state this kind of disease is transmitted by a prion (misfolded protein), although other studies show that Spiroplasma bacteria may be involved in the transmission, too.
Other diseases in the transmissible spongiform encephalopathy (TSE) group are Creutzfeldt-Jakob disease in humans, mad cow disease in cattle, and scrapie in sheep. Although chronic wasting disease is primarily found in deer, experimental transmission to squirrel monkeys and genetically modified mice was successful. Other animals that came into direct or indirect contact with infected deer were cattle, goats, and sheep. They showed no signs of transmission.
The first CWD case was found in 1967 in the United States. However, only in 1978 had specialists officially named it the “Chronic Wasting Disease.” Until then, they thought it was a clinical “wasting” syndrome, also called cachexia, which causes muscle loss. The first case in Canada was identified in 1996.
Over the years, this disease was identified in deer in four Canadian provinces, 30 US states, Finland, Sweden, and South Korea. Most cases are in North America, though, and the ones found in South Korea were identified in deer imported from Canada.
Between 2007 and 2018, the MFFP ministry in Quebec did 9,500 tests, and a seropositive case appeared in September 2018. More than 3,000 animals were slaughtered, and 9.8 inches of soil over the 990-acre territory were decontaminated. Before being released into the market, each animal was tested for CWD.
Chronic wasting disease was found in red deer, white-tailed deer, moose, caribou, sika deer, elk, and mule deer – and that’s only in the United States.
How Does Chronic Wasting Disease Affect Deer?
The first Chronic Wasting Disease symptoms occur 18 to 24 months after initial exposure. This means most deer are already adults when they show symptoms.
The first symptoms are difficulties in movement and weight loss over time. Some deer may also show changes in behavior, which means they’ll interact less with other animals, show tremors and nervousness, lower their heads, and perform repetitive walking in set patterns.
Other deer can also exhibit teeth grinding, excessive salivation, increased drinking, and urination. Another alarming sign is if the deer looks confused and isn’t afraid of people.
Unfortunately, this illness is progressive and always fatal.
How Do Deer Get CWD?
Chronic wasting disease is caused by a prion, a misfolded protein found in the central and peripheral nervous systems. This misfolded protein form can change the form of the normally folded prion protein. This, in turn, causes a chain reaction.
It still needs to be discovered how these prions are spread among animals. However, recent studies show that deer and elk may excrete prions, which eventually grow and develop in the soil and are spread by eating grass. Prions can survive many years in the environment. That’s why they’re dangerous, and severe decontamination must be performed.
Moreover, other studies show that an infected deer’s saliva can transmit these prions to other deer.
Can Humans Get CWD?
There haven’t yet been any confirmed chronic wasting disease cases in humans. However, some scientists believe that, since this disease may be spread to other animals, such as mice or monkeys, it may still be a risk to humans. Therefore, the deer introduced into the market are thoroughly screened and tested for CWD.
Chronic Wasting Disease Spread Prevention
Nowadays, many states have established that hunters who harvest deer must have the deer tested for chronic wasting disease. For example, Texas hunters who harvest red deer, elk, mule deer, white-tailed deer, or other deer species prone to getting CWD must bring the animals to a Texas Parks and Wildlife Department check station within 48 hours.
Moreover, the CDC highly recommends checking the state’s wildlife and public health guidance beforehand to see if there have been any CWD cases in the area and if testing is required.
What Is the Human Version of CWD?
The human version of deer chronic wasting disease is called Creutzfeldt-Jakob disease (CJD), sometimes called neurocognitive disorder due to prion disease or subacute spongiform encephalopathy.
It is a fatal degenerative brain disorder that causes symptoms such as behavioral changes, visual disturbances, poor coordination, memory loss, weakness, dementia, and coma.
This disease is transmitted by contaminated harvested human brain products, implants, and human growth hormones, as well as by corneal or dural grafts. Some scientists believe humans can also get this disease from bovine spongiform encephalopathy (the cattle version of CWD), although this isn’t confirmed.
Is CWD the Same as Mad Cow Disease?
Mad cow disease is the cattle version of deer chronic wasting disease. This disease is also called bovine spongiform encephalopathy. Like in deer, this illness causes cattle to exhibit abnormal behavior, weight loss, and trouble walking. Additionally, cows may produce less milk and develop ear infections and teeth grinding associated with pain.
Unlike chronic wasting disease, which is believed not to be transmissible to humans (although this is still debatable), some scientists consider that mad cow disease can be spread to humans who eat contaminated food, especially the brain, digestive tract, and spinal cord.
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- Wikipedia, Available here: https://en.wikipedia.org/wiki/Transmissible_spongiform_encephalopathy
- CDC, Available here: https://www.cdc.gov/prions/cwd/index.html#:~:text=To%20date%2C%20there%20have%20been,from%20infected%20deer%20or%20elk.
- Texas Parks and Wildlife Department, Available here: https://tpwd.texas.gov/huntwild/wild/diseases/cwd/
- CDC, Available here: https://www.cdc.gov/prions/cwd/prevention.html