Introduction
Chronic wasting disease (CWD) is a devastating illness affecting deer, elk, and other ungulates. It is a prion disease, meaning it is caused by misfolded proteins that accumulate in the brain, leading to neurological damage and death. There is a lively debate about whether CWD can affect human health if humans consume affected animals or are otherwise exposed to the disease. This article will explore the current state of scientific research on the risks of CWD in humans, including the uncertainties and known challenges that scientists encounter while studying this illness and its potential transmission mechanisms.
The Intriguing Controversy Surrounding Chronic Wasting Disease in Humans
Chronic wasting disease was first identified in deer in Colorado in the 1960s. Since then, it has spread to other parts of North America, infecting not only wild deer and elk but also captive populations used for hunting, farm-raised species, and other animals. The first known case of CWD in a human did not occur until 1996, when a young man died in New Mexico of a rare prion disease believed to be contracted from eating contaminated elk meat. Since then, several more cases of human prion disease have been linked to CWD, but the exact number is uncertain.
The possibility that CWD can jump the species barrier and infect humans has led to intense scrutiny by scientists, policymakers, and the public alike. Concerns have risen partly because CWD is currently incurable, and current intervention strategies focus on preventing spread among wildlife rather than mitigating its effects on humans. At the same time, some continue to argue that the risks of human infection from CWD are overblown and unsupported by rigorous evidence.
Is Chronic Wasting Disease a Real Threat to Human Health?
To date, there is no definitive evidence that CWD can infect humans, and a significant body of research has concluded that the risks are low. However, the lack of evidence does not necessarily mean that there is no risk. Researchers acknowledge the difficulty of studying rare diseases, and CWD is an example of such a disease, both in animals and humans. Limited information and available data pose several obstacles in deducing the potential impact of CWD infection on human health.
Transmission of CWD to humans likely occurs through the consumption of contaminated meat from infected animals, but studies have shown that prions can also survive in the environment and contaminating soil and water. Browsing mechanisms, where deer and other animals share feed and water sources, also have been identified as potential mechanisms for disease transmission.
Further complicating the situation, the incubation period for CWD in humans and the duration of initial symptoms remain unexplored. Most prion diseases have long incubation periods, sometimes taking decades for symptoms to develop. Thus, definitive diagnosis for CWD, and separating it from other prion diseases in humans, could be challenging and could, in fact, lead to difficulties in studying incidence rates.
The Unknowns and Knowns of Humans Contracting Chronic Wasting Disease
CWD can have severe consequences for affected animals, leading to a wide range of symptoms such as weight loss, behavioral changes, hyperactivity, and eventually death. However, the symptoms and impact of CWD on humans remain unknown, and researchers have only begun to investigate the potential effects of CWD on humans.
One of the most significant challenges in studying the relationship between CWD in animals and humans lies in the difficulty of extrapolating the results from animal studies to humans. Until there is more robust evidence, researchers can only make educated guesses about how much of a threat CWD represents to human health.
Diagnosis of CWD in humans is also complex, as there is no definitive biological test for this disease. Currently, researchers must rely on brain biopsies or autopsies. Still, these tests are impractical and often require samples from the brain and other tissues or fluids, leading to ethical and logistical challenges associated with obtaining samples.
Exploring The Possibility of Chronic Wasting Disease Transmission to Humans
Scientists and public health officials have explored various potential mechanisms by which CWD could potentially infect humans, including the consumption of infected meat and contact with contaminated surfaces or environments. Additional transmission pathways include exposure through transplantation of human or animal tissues or even zoonotic transfer from a natural reservoir.
So far, research on potential transmission has been restricted to non-human primates since ethically, human research would raise significant concerns. Findings have suggested that the transmission of CWD to non-human primates is possible and raises more questions than answers, including how closely prion proteins must match between the donor species and the receiving host for transmission to occur.
The Surprising Similarities and Differences Between Chronic Wasting Disease in Animals and Humans
The prions responsible for CWD in deer and elk share many similarities with the prions that cause other animal and human prion diseases, such as Creutzfeldt-Jakob disease and mad cow disease. Although there are significant differences among these diseases, they all involve prion proteins and are linked to similar neurological symptoms.
However, differences in prion protein structures and between animal and human biology complicate the study of cross-species transmission. While humans are known to be susceptible to some prion diseases, the ability of humans to contract prion strains from animals is relatively unpredictable and may depend on a variety of factors such as genetics and exposure pathways
Chronic wasting disease’s impact extends beyond human health and animal populations, posing far-reaching consequences for our environment and human-animal relationships. For example, efforts to control CWD often include hunting regimes that can interfere with traditional practices of Indigenous populations or affect animal populations and biodiversity in the ecosystem.
Conclusion
As researchers continue to investigate the risks associated with CWD in humans, many questions remain unanswered. Although there is no definitive evidence that CWD can infect humans, the risk of transmission exists. Moreover, several unknowns must be understood better, from incubation periods to the potential exposure mechanisms, to definitively say how much of a risk CWD poses to human health. To ensure adequate prevention and management of this disease in humans and animals, further research, and public engagement are needed.
