#18,571
Six years ago we looked at the spread of Chronic Wasting Disease (CWD) in Deer and Elk (see mBio: Chronic Wasting Disease in Cervids: Implications For Prion Transmission To Humans & Other Animals) both in the United States and Canada.
That mBio article noted the spread of CWD (in 2000, only 5 States reported the disease), and its zoonotic potential. While human cases had not been identified, it may take years for the disease to manifest in humans, and even then diagnosing it could be challenging.
The authors (including Michael T. Osterholm) wrote:
Three weeks ago the USGS updated their CWD map for 2024 (see above), stating that `. . . CWD has been detected in free-ranging cervids in 35 states and four provinces and in captive cervid facilities in 22 states and three provinces.'Available data indicate that the incidence of CWD in cervids is increasing and that the potential exists for transmission to humans and subsequent human disease. Given the long incubation period of prion-associated conditions, improving public health measures now to prevent human exposure to CWD prions and to further understand the potential risk to humans may reduce the likelihood of a BSE-like event in the years to come.
Less than 2 weeks ago CIDRAP - which has long championed research into CWD - released an extensive (102-page) report (see below) on the disease, which is very much worth reading.
Center for Infectious Disease Research and Policy (CIDRAP), University of Minnesota. Chronic Wasting Disease Spillover Preparedness and Response: Charting an Uncertain Future. 2025 Jan 8. Available at: https://www.cidrap.umn.edu/chronic-wasting-disease/cwd-spillover-report-2025
CWD is one of several prion-related transmissible spongiform encephalopathies (TSEs) that occur in animals and humans. Other examples include Creutzfeldt-Jakob disease (CJD), variant CJD (vCJD), and kuru, which occur in humans; bovine spongiform encephalopathy (BSE, or “mad cow disease”), which occurs in cattle and has been transmitted to humans, causing vCJD; and scrapie, which occurs in sheep and goats.In the 1980s and 1990s the UK beef industry was rocked by an outbreak of bovine spongiform encephalopathy (BSE), which infected hundreds of thousands of cows, and killed at least 178 people. More than 4.4 million head of cattle were destroyed, and the economic costs ran into the billions.
BSE was first diagnosed in 1986 in Great Britain. Since then, more than 185,000 cases have been confirmed worldwide. More than 95 percent of these have occurred in the United Kingdom, but the disease has also been confirmed in native-born cattle in the following countries: Austria, Belgium, Canada, the Czech Republic, Denmark, Finland, France, Germany, Greece, Ireland, Israel, Italy, Japan, Luxembourg, Liechtenstein, the Netherlands, Poland, Portugal, Slovakia, Slovenia, Spain, Switzerland, and the U.S.
Five cases of BSE have been identified in the U.S. The first case in 2003 was confirmed as C-type BSE and the subsequent four cases were confirmed as atypical BSE forms. The first case was detected in 2003 in Washington State in a 6 year-old dairy cow imported from Canada. The second, in 2005, was a 12 year-old beef cow in Texas. The third, in 2006, was a 10 year-old beef cow in Alabama. The fourth, in 2012, was a 10 year-old dairy cow in California. The fifth case, in 2017, was an 11 year-old beef cow in Alabama. As a result, U.S. beef exports dropped 80% after 2003 and have not yet fully recovered. It was not until May 2017 that China allowed U.S. beef exports to flow directly to the country since 2003 when the C-type BSE case was confirmed in U.S.
Detection of Chronic Wasting Disease Prions in Raw, Processed, and Cooked Elk Meat, Texas, USA
Rebeca Benavente, Fraser Brydon, Francisca Bravo-Risi, Paulina Soto, J. Hunter Reed, Mitch Lockwood, Glenn Telling, Marcelo A. Barria, and Rodrigo Morales
Abstract
We describe chronic wasting disease (CWD) prion detection in raw and cooked meat from a CWD-positive elk. We found limited zoonotic potential in CWD prions from those meat products. Nonetheless, risk for transmission to humans is still unclear, and monitoring of circulating and emerging CWD prion strains for zoonotic potential is warranted.
Prion diseases cause various diseases that affect several animal species, including scrapie in sheep and goats (1), Creutzfeldt-Jakob disease (CJD) in humans (2,3), bovine spongiform encephalopathy (BSE) in cattle (4), and chronic wasting disease (CWD) in cervids (5). In the 1990s, several atypical CJD cases occurred among persons who ingested cattle-derived products infected with BSE. Those cases later were attributed to the emergence of a new human prion strain templated by BSE prions (6). Subsequent studies have been conducted to investigate the zoonotic potential of other prionopathies, including CWD (7,8). Although no cases of CWD transmission to humans have been reported, the potential for human infection is still unclear because contradictory results have been reported from studies in animal models, in vitro systems, and nonhuman primates (8,9).
(SNIP)
The Study
We obtained different unprocessed and processed meats from a hunter-harvested, CWD-infected elk that encoded both methionine and leucine polymorphic variations at prion protein (PrP) position 132. We used meat and meat-derived products, including filets, jerky steak cuts, hamburger meat, chili meat, sausage, ham, cutlets, and boneless steaks (Appendix Figure 1). The meat was prepared from a 5-year-old bull elk (Cervus elaphus nelsoni) that was positive for PrPSc (scrapie isoform of the prion protein) in the obex region of the brain; lymph node was not tested. The elk was harvested on December 10, 2020, and the sample was confirmed as CWD-positive January 8, 2021. The animal was collected in Medina County, Texas, on a private high-fenced hunting ranch.(SNIP)ConclusionsOverall, our study results confirm previous reports describing the presence of CWD prions in elk muscles (13). The data also demonstrated CWD prion persistence in food products even after processing through different procedures, including the addition of salts, spices, and other edible elements. Of note, our data show that exposure to high temperatures used to cook the meat increased the availability of prions for in vitro amplification. Considering the potential implications in food safety and public health, we believe that the findings described in this study warrant further research.Our results suggest that although the elk meat used in this study resisted different manipulations involved in subsequent consumption by humans, their zoonotic potential was limited. Nevertheless, even though no cases of CWD transmission to human have been reported, the potential for human infection is still unclear and continued monitoring for zoonotic potential is warranted.
Ms. Benavente is a master’s student and graduate research assistant at the Department of Neurology, McGovern Medical School, The University of Texas Health Science Center in Houston, Texas, USA. Her research focuses on developing methods for prion detection and drug discovery, as well as risk factors contributing to the spread of CWD.
While it is somewhat reassuring that no humans have been diagnosed with this particular form of CWD, similar prion diseases have demonstrated a wide host range. This from the USDA:
Sheep, goats, mink, deer, and elk can get sick with their own versions of BSE. Cats are the only common household pet known to have a version of BSE. It is called feline spongiform encephalopathy, and the same things that are being done to protect people and cows are also protecting cats. No cat in the U.S. has ever been found to have this disease.
Returning to the first of nine recommendations in the CIDRAP Report, the authors write:
There is a risk of CWD spillover to other wildlife, non-cervid production animals, and humans. The risk of CWD spillover is not static and may be increasing as new strains emerge and exposure probabilities increase. Historical data may not be a reliable predictor of current or future spillover risk. As a result, there are growing needs for:
⯁ Additional capacity and infrastructure to support CWD research, diagnostic innovation, and preparedness;
⯁ New communication strategies to inform policymakers and stakeholders who would be responsible for a successful CWD spillover identification and response; and,
⯁ Advanced planning, in particular multiagency tabletop exercises to prepare consistent and coordinated CWD spillover policies and response plans.
Even without the zoonotic potential, CWD could have a devastating impact on U.S. meat production, potentially on a scale far greater than what the UK experienced 40 years ago.
Making it a topic very much worthy of our attention.
