HUMAN RISK REAL? ASSESSING THE POTENTIAL TRANSMISSION OF "ZOMBIE DEER DISEASE"

Medically Reviewed by Dr. Sony Sherpa (MBBS) - August 9, 2024

In recent years, a disease impacting deer, elk, and moose populations in North America has been steadily growing. This disease, known as Chronic Wasting Disease (CWD) or "Zombie Deer Disease," has been found in Yellowstone Park recently, making headlines due to its potential for animal to human spread.

The nickname comes from the unusual behavior infected deer can show, like stumbling, drooling, and appearing lethargic, resembling the fictional "zombies." Once infected, animals inevitably succumb. Sadly, there is no cure or vaccine for CWD. The possibility of a "slow-moving disaster" highlights the importance of understanding and preventing its spread.

This blog closely examines the facts about CWD and its potential health impact on humans.

What is Chronic Wasting Disease (CWD)?

CWD is a terminal condition that affects the nervous systems of deer, elk, and moose. It is progressive and fatal, affecting the nervous system of infected animals. The disease slowly damages the brain, leading to weight loss, abnormal behavior, and eventual death. These manifestations are not due to a zombie deer virus.

Zombie Deer Disease is caused by an infectious protein called a prion, similar to the prion that causes Mad Cow Disease in cattle^[1]. These illnesses belong to a group of diseases known as spongiform encephalopathies due to the way they create a sponge-like appearance in brain tissues.^[2]

Healthy prions reside throughout the nervous systems of animals and humans. Their functions remain undetermined, although some evidence suggests that they are responsible for binding to neuronal proteins to enable various functions, including nerve myelination. Prions may also cause some of the problems seen in Alzheimer's Disease and Parkinson's disease.

The first case of CWD was identified in captive mule deer in Colorado in the late 1960s. Since then, reports of infected wild deer, elk, and moose appeared in 26 states in the US and three Canadian provinces. It is most prevalent in the Midwest and Rocky Mountain regions but also leaves a trail in other areas such as Texas, New York, and even as far as South Korea.

CWD Transmission

CWD transmission occurs through contact with infected body fluids, such as saliva, blood, urine, and feces.

Contaminated soil, plants, and water can also transmit the disease. Prions can linger in soil and on plants for years, even after an infected animal dies. These silent danger zones can pass the disease to healthy animals who wander through.

Signs and Symptoms of "Zombie Deer"

Infected deer often show unusual behavior that indeed credits the condition's nickname 'Zombie Deer.'

Zombie Deer Symptoms include:

• Weight Loss
• Loss of coordination
• Excessive drooling
• Tremors
• Blank stares
• Aggression

Symptoms can take months or even years to show in infected animals. This prion “incubation period” makes CWD especially tricky to track and control. Other illnesses can also cause these symptoms. Testing is crucial to confirm CWD and avoid misdiagnoses.

While these symptoms may seem terrible, there is no evidence to prove that CWD is transmissible to humans. Nevertheless, CWD is an actual disease caused by an infectious protein called a prion. Even if it was contagious, it is unrelated to zombies or any supernatural phenomenon.

Diagnosis

Currently, the most reliable way to diagnose CWD is through post-mortem testing of the affected animal’s brain tissue^[3]. These tests scan for harmful prion proteins.

Scientists are developing live-animal testing. However, this is yet to be widely available.

CWD Control and Prevention

The CDC and other institutions are actively working to contain and prevent the spread of CWD^[4]. Some suggested preventive measures include:

• Monitoring and testing of wild and captive deer, elk, and moose populations
• Implementing regulations for the transportation of deer, elk, and moose carcasses
• Educating hunters and the public about the disease and how to prevent its spread
• Instituting hunting regulations and proper carcass disposal
• Researching potential treatments or vaccines for CWD

It is essential to rely on accurate news from trustworthy authorities, such as the Centers for Disease Control and Prevention (CDC) and wildlife agencies to understand the facts about CWD and its potential impact on humans.

Can CWD be Transmitted to Humans?

There is currently no evidence that CWD transmission affects humans, but there is also no evidence to show that it cannot. The Centers for Disease Control and Prevention (CDC) states that while the risk of CWD transmission to humans is low, it cannot be ruled out at the moment.

Scientists are studying this possibility cautiously. A preliminary study reveals that scientists can get CWD prions to infect human and mouse tissues with slight modifications.

As explained, some diseases like mad cow have spread from animals to humans.

While just speculation, a spillover event may happen in the future. A spillover event occurs when a disease typically found in one species jumps to another. Spillovers can happen when humans come in contact with infected animals or their body fluids.

In the case of CWD, a spillover event has never happened before. However, experts warn that it may be possible for a human to consume infected meat or come into contact with infected body fluids without taking necessary precautions.

Can CWD Enter the Human Food Chain?

While no confirmed human cases exist, CWD might enter the food chain by consumption of infected venison. Cooking meat at high temperatures does not permanently destroy prions, as demonstrated in mad cow disease-infected beef.^[5]

The CDC recommends hunters who harvest deer, elk, or moose from areas where CWD is recorded to have their animals tested for the disease before consuming the meat. If the animal tests positive for CWD, it is recommended not to consume the meat.

What is Being Done to Protect Humans from CWD?

Aside from consumption warnings, the CDC has issued guidelines for hunters and others who may come into contact with CWD-infected deer, elk, or moose, such as:

• Do not handle or consume meat from animals that seem sick or have confirmed CWD.
• Wear gloves when field dressing and processing deer, elk, or moose.
• Avoid touching brain and spinal cord tissues as much as possible, as these are the most likely to contain prions.
• Thoroughly clean and disinfect tools and surfaces used for processing animals.
• Avoid consuming the brain, spinal cord, eyes, spleen, tonsils, and lymph nodes of deer, elk, or moose.
• Follow state and local laws regarding transporting deer, elk, or moose carcasses.
• Support research efforts to uncover more about this potentially alarming disease, such as reporting infected animals or testing live ones.

Conclusion

While there is currently no evidence that CWD transmission can occur from animals to humans, the potential for a spillover event is a cause for concern. The CDC and other associations are actively working to control and prevent the spread of CWD. Still, more research is needed to fully understand the disease and its potential impact on humans. In the meantime, it is crucial to follow guidelines and precautions to lower the possibility of exposure to CWD.

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