The strain properties of Korean and North American CWD prions are indistinguishable

Authors: HYUN JOO, SOHN - Animal And Plant Quarantine Agency; JOSEPH, DEFRANCO - Colorado State University; HOO-CHANG, PARK - Animal And Plant Quarantine Agency; KYUNG JE, PARK - Animal And Plant Quarantine Agency; Bian, Jifeng; JENNA, CROWELL - Colorado State University; SEHUN, WEBSTER - Colorado State University; BAILEY, WEBSTER - Colorado State University; HAE-EUN, KANG - Animal And Plant Quarantine Agency; GLENN, TELLING - Colorado State University

Submitted to: Journal of Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Chronic Wasting Disease (CWD) was first identified in North America in 1967, affecting deer, elk, and other cervids. In mid-1990s, several groups of elk that appeared healthy but were actually infected with CWD were accidentally exported from North America to South Korea. This led to the introduction of CWD into South Korea’s farmed cervid populations, where the disease became established. Despite efforts to control the outbreak—such as culling infected animals, repopulating farms with CWD-free cervids from other countries, and decontaminating affected farms—CWD continues to persist in South Korea. This ongoing outbreak provides a unique opportunity to study whether the CWD prion strain in South Korea has changed over time compared to the original North American strain. Our systematic studies, using cell culture models, transgenic mice, and gene-targeted mice, found no significant differences between the CWD strains from North America and South Korea. These findings suggest that a single, dominant CWD prion strain remains responsible for infections in both regions, despite years of disease circulation and attempted control measures. This is distinct from the various CWD strains that have emerged in Europe since 2016, which have shown significant differences from North American strains. European cases—detected in reindeer, moose, and red deer—suggest the possibility of spontaneous prion emergence rather than direct introduction from North America.

Technical Abstract: Background. Chronic wasting disease (CWD) is an ineradicable prion epidemic affecting wild and farmed cervids in North America. While CWD was introduced to South Korea (SK) by importation of sub-clinically diseased elk from North America, it is unclear whether CWD in SK represents a bottleneck infection by an uncommon North American strain, or whether variant derivatives have evolved during subsequent transmissions in novel SK cervid species. Methods. We propagated prions from the brains of diseased SK cervids to multiple lines of genetically-modified mice designed to be susceptible to CWD. We characterized the strain properties of these SK CWD prions by evaluating disease outcomes and the infectious and biochemical properties of the resulting prions. Results. SK and North American CWD prions had comparable disease kinetics during iterative transmissions in transgenic and gene targeted mice. The biochemical properties, including conformational stability, and infectivity profiles of propagated SK CWD prions were also indistinguishable from those of North American CWD prions. Conclusion. These overlapping properties are consistent with infection of SK and North American cervids by the same CWD prion strain. Our findings contribute to an emerging picture in which an established, dominant prion strain is responsible for contagious CWD transmission among North American and SK cervids with properties distinct from the highly divergent and relatively unstable CWD prion strains causing emergent infections in moose, reindeer, and red deer from Northern Europe.