Chronic Wasting Disease (Zombie Deer): Could It Affect Humans?

Understanding Zombie Deer Disease and Its Spread Across the U.S.

Zombie deer disease, more formally known as chronic wasting disease (CWD), has emerged as a serious concern across the United States over the past few decades. Since it was first identified in the late 1960s, CWD has spread to deer and elk herds across at least 32 U.S. states and several Canadian provinces. The relentless spread of this fatal, brain-wasting disease has many experts worried it could eventually jump to humans, similar to how mad cow disease infected people in the 1990s.

What Is Zombie Deer Disease?

Zombie deer disease or CWD is a fatal neurological illness found in cervids, the family of hoofed animals including deer, elk, reindeer, and moose. It is caused by an abnormally shaped protein called a prion, which triggers normal, healthy proteins in the brain to misfold and cause damage over time. This leads to brain lesions and neurodegeneration.

CWD is part of a group of prion diseases known as transmissible spongiform encephalopathies (TSEs), which includes mad cow disease in cattle and Creutzfeldt-Jakob disease in humans. These diseases cause sponge-like holes and protein clumps to form in the brain, severely impacting neurological function until death ultimately occurs.

Key Facts About Zombie Deer Disease

Here are some key facts to know about chronic wasting disease:

• It is fatal - there is no vaccine or treatment available.
• Has a long incubation period - deer may not show symptoms for over a year after becoming infected.
• Causes dramatic weight loss and wasting in the late stages, giving it the "wasting" name.
• Impacts brain function - infected deer often display abnormal behavior and lack of coordination.
• Spreads through prions in bodily fluids - prions bind to soil, plants, and remain infectious for years.
• Prions are incredibly resistant - they do not degrade easily and require very high heat or harsh chemicals to be fully inactivated.
• Affects cervids like deer, elk, moose, and reindeer so far but has been found in some non-cervid animals too.

How Zombie Deer Disease Spreads

The exact origin of CWD remains unknown, but it was first recognized as a disease syndrome in 1967 in captive mule deer in Colorado. Since then, it has spread steadily across continental deer herds and another TSE of deer across the ocean in Norway. The disease transmission occurs through both direct animal-to-animal contact and through environmental exposure to lingering prions in the environment like soil, food, and water. The primary routes of CWD transmission include:

• Animal bodily fluids - urine, feces, saliva, and blood carry prions, allowing CWD to spread through contact with these fluids.
• Contaminated environments - prions bind tightly to soil minerals once shed from the body and remain infectious for years.
• Shared feed and minerals - prions spread through common food and mineral sources that multiple deer contact and ingest.
• Mother to offspring - pregnant does can pass prions on to developing fawns.
• Contact with carcasses - both animals and humans can contract prions through handling infected deer carcasses.

The efficient transmission of CWD through bodily fluids and environmental reservoirs has allowed it to spread widely across wild cervids in certain hot zones, reaching infection rates over 30% in some populations. The disease prevalence has spawned the alarming zombie deer nickname when infected animals begin to display vacant stares, drooling, lack of fear of humans, and emaciation in the later disease stages.

Distribution of Zombie Deer Disease in the U.S.

Since the identification of CWD more than 50 years ago, the disease has been detected across at least 32 U.S. states and several Canadian provinces as of early 2023. The known distribution includes:

• Western states like Colorado, Wyoming, Montana, Utah, Nebraska
• Midwestern states such as Wisconsin, Illinois, Michigan, Minnesota
• Northeastern states including New York, Pennsylvania, Maryland, West Virginia
• Southeastern states like Arkansas, Mississippi, North Carolina, Virginia
• South-central states including Texas and Oklahoma

Some states have especially high CWD prevalence rates, such as Wisconsin where over 50% of deer are infected in certain counties. The disease is most entrenched in northern portions of Colorado and Wyoming where it has existed the longest. The combined effects of wildlife management practices, interconnected habitat, and animal migrations have fueled the expanding geographical reach of CWD over time. Experts are especially concerned about its spread to new regions through human transportation of infected deer carcasses and movement of live animals.

Impact on Deer and Elk Populations

The consequences of chronic wasting disease for already distressed deer populations across North America could be devastating, although the full impacts are not yet known. Some observed and potential effects on cervids include:

• High mortality rates - CWD is always fatal once clinical signs emerge.
• Shorter lifespans - infected animals tend to die at younger ages than uninfected individuals.
• Lower reproduction - birth rates are lower among infected deer and elk.
• Altered behaviors - diseased animals display erratic behaviors that make them vulnerable to accidents, predation, and human interaction.
• Wasting and weakness - late-stage illness leaves animals severely emaciated and weak.
• Potential local extinction - deer may disappear from some zones with extremely high infection prevalence.

Severe CWD outbreaks could compound wider challenges that deer populations already face, including habitat loss, car collisions, starvation, pathogens, toxins, and overhunting. State wildlife agencies and the U.S. Centers for Disease Control closely monitor the spread of zombie deer disease and work to limit its impact through strategies like reduced hunting quotas, deer culls, and carcass regulations.

Risk of Zombie Deer Disease Spreading to Humans

While CWD so far has affected only deer, elk, and related species, many health experts fear it could make the jump to humans in the future. This is what occurred with mad cow disease in the 1990s, as people developed a human form called variant Creutzfeldt-Jakob disease from eating beef contaminated with bovine prions. Zombie deer proponents argue a similar scenario could unfold with hunters handling and consuming CWD-infected venison.

It remains unknown whether CWD prions can infect people and cause disease. Limited epidemiological research has not linked CWD exposure to increased Creutzfeldt-Jakob disease prevalence, but experts caution that a rare cross-species jump could still occur given the long incubation period. The potential avenues of human exposure to CWD prions include:

• Eating infected deer meat if prions enter the food supply.
• Handling carcasses and harvested animals during field dressing.
• Coming in contact with contaminated environments where sick deer reside.
• Using knives or taxidermy equipment exposed to prions.
• Consuming prions that survived inadequate meat cooking temperatures.

There are currently no direct documented cases of humans contracting a TSE from North American deer. But research in monkeys has found that consuming infected meat can deliver CWD prions to the digestive system. The CDC recommends hunters take precautions like wearing gloves, minimizing carcass handling, and avoiding consumption of deer appearing ill.

Detection and Diagnosis of Zombie Deer Disease

Early diagnosis of CWD is challenging since infected deer show no clinical signs for at least 16 months on average. Diagnostic testing relies on tissue samples of lymph nodes or obex brain stem tissue collected after the animal’s death. Biopsies of lymphoid tissue in the tonsils of live deer can also detect CWD. Scientists use the following methods to identify prions:

• Immunohistochemistry - prion proteins leave distinct microscopic deposits in tissues.
• Protein misfolding assays - assess abnormal prion protein folding patterns.
• Western blot - identifies prion protein bands by molecular weight.

Postmortem testing provides the most reliable CWD diagnosis but cannot help symptomatic live animals. Researchers continue working to develop improved premortem screening techniques to catch CWD infections sooner. Current assays also cannot detect prions at extremely low concentrations, meaning some positives get missed.

Management and Prevention Strategies

While zombie deer disease continues spreading across the landscape, wildlife agencies employ various management efforts to monitor its prevalence and slow its growth. Some common CWD management strategies include:

• Surveillance testing of hunter-harvested and roadkill deer.
• Restrictions on carcass transportation from affected areas.
• Bans on artificial deer urine lures to avoid contamination.
• Selective culling in hot zones to thin herds and slow transmission.
• Restricted supplemental feeding to prevent deer congregating.
• Hunting quotas and limited doe tags where infection is high.
• Safety guidance for hunters around carcass handling and meat preparation.

Even with reasonably effective management, eliminating CWD from wild deer populations is extremely unlikely at this point. The disease is simply too entrenched in certain zones. Ongoing research focuses on improving diagnostics, developing potential therapies, creating CWD resistant deer genotypes, and conducting epidemiological studies to better understand transmission risks. Increased public awareness and vigilance are critical to limiting the consequences of prion exposure.

The Future of Zombie Deer Disease

The sobering reality is that CWD will likely remain present across U.S. cervid populations indefinitely given its stealthy nature and efficient transmission. This persistence may eventually pose serious consequences for already pressured deer and elk herds. While human infection has not been confirmed yet, it also remains a possibility health experts take seriously based on past prion disease epidemics.

Ongoing surveillance, management adaptations, hunter education, and research into CWD prevention represent the best hopes for containing zombie deer disease long-term. CWD serves as an example of how microscopic protein folding gone awry can have expansive ecological impacts. Awareness and prudent actions around affected animals and environments offer the best protection against further uncontrolled spread of this perplexing illness.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.