The Unlikelihood of Chronic Wasting Disease Transmission to Humans

Chronic Wasting Disease (CWD) is a prion disease that primarily affects cervids, but there have been concerns about its potential to infect humans. Recent data from the National Institute of Allergy and Infectious Diseases (NIAID) and Rocky Mountain Laboratories provide new insights into the species barrier that prevents the transmission of CWD to humans.

The study conducted by Cathryn Haigh, PhD, and her colleagues exposed healthy human cerebral organoids to high concentrations of CWD inocula from white-tailed deer, mule deer, and elk for 7 days. Despite the prolonged exposure, the organoids remained uninfected with CWD for up to 6 months. This suggests a substantial species barrier that prevents the transmission of CWD from cervids to humans.

Unlike CWD, another prion disease, bovine spongiform encephalopathy, has been known to transmit to humans and cause variant Creutzfeldt-Jakob disease (CJD). However, the recent study shows that CWD does not pose the same zoonotic threat as bovine spongiform encephalopathy.

At the American Academy of Neurology annual meeting, a case study was presented involving a 72-year-old man who consumed meat from a CWD-infected deer population. Despite showing symptoms similar to CJD, no definitive evidence of CWD infection was found. Non-human primate and mouse models have shown that cross-species transmission of CJD is plausible, but the study indicates that CWD may not be as easily transmittable to humans.

Research Findings and Conclusion

The NIAID researchers used human cerebral organoids to test the infectivity of CWD on human neural tissue. Despite the high concentrations of CWD inocula used in the experiment, the organoids did not propagate CWD prions. This highlights the strong species barrier that exists between cervids and humans. While the possibility of CWD crossing into humans cannot be completely ruled out, the data suggests that the risk is minimal.

The study provides valuable insights into the zoonotic potential of CWD and the existence of a robust species barrier that prevents its transmission to humans. Further research is needed to fully understand the implications of CWD exposure in humans, but the current data is reassuring in terms of the risk of CWD infection in human populations.