Does ‘zombie deer disease’ pose risks for humans?

Does 'zombie deer disease' pose risks for humans?

A concerning phenomenon known as “zombie deer disease” is on the rise among wildlife populations, raising questions about its potential transmission to humans. Chronic wasting disease (CWD), categorized as a prion disease by the Centers for Disease Control and Prevention (CDC) in the United States, is a neurodegenerative condition primarily affecting cervids, including deer. Although no cases have been reported in humans thus far, recent confirmations of CWD in deer and moose in Canada, following earlier instances in Yellowstone National Park, underscore its expanding reach.

As CWD spreads across regions spanning North America, Scandinavia, and South Korea, some experts express apprehension regarding the possibility of human transmission. Their concerns stem from experimental studies, historical precedent of prion diseases crossing from animals to humans (albeit rarely), and potential implications of climate change on disease dynamics.

“While no transmission from deer or elk to humans has occurred to date,” explains Jennifer Mullinax, associate professor of wildlife ecology and management at the University of Maryland, “efforts remain steadfast to prevent any prion disease from entering the food chain, given the nature of prions.”

Chronic wasting disease, unlike conventional bacterial or viral infections, is caused by misfolded prion proteins, whose abnormal configuration triggers neurodegeneration. Affected animals exhibit a range of symptoms, including weight loss, altered behavior, and neurological impairment, earning the condition its evocative moniker, “zombie deer disease.” Transmission occurs through direct contact with bodily fluids, waste, contaminated environments, or contaminated food sources.

While current evidence does not confirm CWD transmission to humans through consumption of infected meat or exposure to contaminated environments, ongoing research explores this possibility. Previous studies, such as a 2011 CDC investigation involving over 17,000 participants, yielded no evidence of human transmission from CWD-infected sources.

However, prion diseases, including Creutzfeldt-Jakob Disease (CJD) and its variant (vCJD), have affected humans. The emergence of vCJD in 1996, linked to bovine spongiform encephalopathy (BSE), or “mad cow” disease, illustrates the potential risks associated with zoonotic transmission.

In 2018, a National Institutes of Health study found no evidence of CWD transmission to macaques, a species genetically close to humans. Yet, other research, like a 2022 study from the University of Calgary, suggests potential transmission to humanized mice, underscoring the need for further investigation.

As concerns grow, experts emphasize vigilance and ongoing surveillance efforts. Initiatives such as CIDRAP’s contingency planning and research on live testing for CWD aim to mitigate risks associated with potential human exposure. However, uncertainties persist, compounded by the dynamic interplay of environmental factors, disease evolution, and wildlife demographics, highlighting the need for continued vigilance and collaborative research efforts in confronting the complexities of “zombie deer disease.”