Chronic wasting disease: the growing threat of zombie deer disease

Across the quiet woodlands and grasslands of North America, a worrying phenomenon is unfolding largely unseen: chronic wasting disease (CWD). Often called “zombie deer disease”, the condition is spreading discreetly through deer populations, causing concern among scientists, conservationists and the public.

The neurological disease can produce a wide range of symptoms, including drooling, lethargy, stumbling and a vacant stare. In Wyoming alone, it has now been detected in more than 800 samples from deer, elk and moose, illustrating both the scale and urgency of the problem.

Chronic wasting disease and prions

A peculiar culprit lies at the centre of the CWD mystery: prions.

These misfolded proteins can cause normal proteins in the brain to misfold too, resulting in neurological degeneration. Prion diseases are especially troubling because prions are notoriously resilient: they can remain in the environment for years and withstand conventional disinfection methods, including formaldehyde, radiation and incineration at extreme temperatures.

Potential human health risks from CWD

The spread of CWD presents substantial ecological risks and potential risks to human health. Although there is no conclusive evidence that CWD can infect people directly, the possibility remains a concern.

Other prion diseases, including Creutzfeldt-Jakob disease (CJD) in humans and “mad cow disease” in cattle, have demonstrated that the species barrier can be crossed, with devastating results. In Britain, for example, the mad cow disease outbreak prompted the slaughter of millions of cattle and has been linked to 178 human deaths from the human variant of the disease since 1995.

Several factors continue to cause concern, even though no human cases of CWD have been confirmed. Studies have shown, for one, that the prions responsible for CWD can infect human cells and reproduce within them under laboratory conditions, raising the possibility of transmission.

People are also already exposed inadvertently to potentially infected animals when they hunt and eat them. Reports suggest that humans consumed between 7,000 and 15,000 CWD-infected animals annually in 2017, with projections pointing to an annual increase of 20 per cent.

In places where CWD is widespread, including Wisconsin, thousands of people may unknowingly have eaten meat from infected deer. This highlights the urgency of taking steps to reduce the risks.

The difficulty of detecting and diagnosing prion diseases in people adds another complication. Unlike conventional infectious agents, prions do not provoke an immune response, so standard detection methods struggle to identify them. This creates a substantial barrier to early intervention and containment.

Direct transmission is not the only possible way CWD could affect human health. Because prions persist in the environment, people could also be exposed indirectly through contaminated soil, water and other environmental sources. Their resilience and ability to remain present for long periods leave the long-term human health consequences uncertain, but deserving of serious consideration.

CWD also brings significant ecological and economic risks beyond the immediate health concerns. Deer hunting is both a popular recreation and an essential source of food and income for many communities. As CWD spreads, it threatens to disturb that delicate balance, potentially decimating deer populations and undermining food security in affected areas.

The ecological consequences could extend beyond deer to entire ecosystems. Through browsing and grazing, deer help shape vegetation dynamics – the way plant communities change and evolve over time. A decline in their numbers could therefore have cascading effects on plant communities, soil health and other wildlife that relies on deer for food or for changes to habitat.

CWD in Europe

Although the UK has experienced no CWD outbreaks, the disease was diagnosed in wild deer in Norway in 2016, representing the first European cases.

That development demonstrates the potential for CWD to extend beyond its present range and underlines the importance of international cooperation to monitor and control it.

Tackling the many challenges of CWD calls for a comprehensive, coordinated response. This means strengthening surveillance and monitoring to follow its spread, alongside stringent biosecurity measures to prevent further transmission. Such measures include controlling the movement of deer and elk populations, testing regularly to track disease prevalence and encouraging responsible hunting practices to minimise transmission risks.

Further research is needed to improve understanding of how the disease spreads, its ecological effects and its possible implications for human health.

Ultimately, the threat of CWD highlights the interconnectedness of ecosystems and human health. By listening to scientists’ warnings and acting decisively to reduce risks, we can work to protect wildlife and people from CWD and other emerging zoonotic diseases. In doing so, we honour our commitment to protecting the health and wellbeing of the planet and its inhabitants for generations to come.

Samuel J. White, Senior Lecturer in Genetic Immunology, Nottingham Trent University, and Philippe B. Wilson, Professor of One Health, Nottingham Trent University

This article is republished from The Conversation under a Creative Commons licence. Read the original article.