CWD continues to spread across North America

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Chronic waste disease (CWD) has been detected in free-ranging cervids in 24 states and 4 provinces as well as in captive cervid facilities in 19 states and 3 provinces. The most recent detection was announced by the California Department of Fish and Wildlife that CWD has been detected within deer and elk in the state.

“CWD is clearly spreading geographically, and increasing in prevalence in locations where it is established,” said Bryan Richards, emerging disease coordinator at the USGS National Wildlife Health Center, in a release published by the American Veterinary Medical Association.¹

Multiple jurisdictions have documented 40-50% positive rates in their adult male samples in areas that are more heavily affected, with some of the same jurisdictions have documented 20-30% positive rates in adult females.² When it comes to responding, aggressive responses to the disease have been limited to a subset of affected states. According to Richards, some states are taking on a more of a monitoring stance and that alone will not alter the outcomes of the disease.

The United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) agency provides states, tribal governments, universities, and more millions of funding to control CWD in wild and farmed cervids. The majority of the funding continues to be allocated to basic research and monitoring, and a smaller portion going to applied research and active management.¹

For veterinary professionals and cooperators, they can reduce the risk of the spreading and infection of CWD in farmed cervid herds by maintaining strict biosecurity and raising cervid species that are less susceptible or resistant to CWD.

“We continue to see CWD spread among captive facilities, with new positive facilities being detected every year,” explained Richards.¹ “How infectious material is being introduced into some of these facilities remains an open question.”

On the differential list for the many facilities with CWD, human-caused introduction of infectious materials remains high with everything from artificial insemination practices to biopsy tools for antemortem testing. Because of this, it is crucial for professionals to do an appropriate and thorough disinfection.

Current research

As the CWD cases continue to rise, researchers are investigating if it is possible to be transmissible to humans. There is currently no evidence showing that this disease can be spread to humans by eating meat from infected animals, encountering an infected animal in the wild, or touching or consuming contaminated soil or water.

“There is currently not enough research to determine whether cross-species prion transmission is possible,” said Tanya Espinosa, public affairs specialist for APHIS.¹

The National Institute of Health’s (NIH) Rocky Mountain Laboratories’ researchers have been testing if this disease could infect human neural tissue.³ They conducted their research by exposing human cerebral organoids with 2 different genotypes, one previously associated with susceptibility to zoonotic prion diseases – to high concentrations of CWD from 3 different sources for a week.

The researchers found that there is no new CWD propagation or deposition of protease-resistant forms of human prions in the CWD-exposed organoids, which had remained uninfected for up to 6 months, suggesting substantial species barrier prevents the transmission of CWD to humans.

More studies are underway to identify if any prion diseases can happen at a higher rate in people who have an increased risk of protease-resistant forms of human prions that are seen in CWD-exposed deer or elk meat. Scientists are expecting the study to take many years before determining what the risks, if any, CWD has to humans since it takes a long time for symptoms of CWD to appear.¹

Reference

1. Chronic wasting disease continues to spread in cervids. American Veterinary Medical Association. News release. June 17, 2024. Accessed June 18, 2024. https://www.avma.org/news/chronic-wasting-disease-continues-spread-cervids
2. Carlson C, Hopkins M, Nguyen N, Richards B, Walsh D, David Walter W. Chronic Wasting Disease: Status, Science, and Management Support by the U.S. Geological Survey Background and Significance. https://pubs.usgs.gov/of/2017/1138/ofr20171138.pdf
3. Groveman BR, Williams K, Race B, et al. Lack of Transmission of Chronic Wasting Disease Prions to Human Cerebral Organoids. Emerg Infect Dis. 2024;30(6):1193-1202. doi:10.3201/eid3006.231568