Prions in Sporadic Chronic Wasting Disease Found Spread throughout the Body in Moose and Red Deer

Prions in Sporadic Chronic Wasting Disease Found Spread throughout the Body in Moose and Red Deer

A new study expands the understanding of where prions can be found in the bodies of moose  (Alces alces) and red deer (Cervus elaphus) with sporadic Chronic Wasting Disease (CWD). Through infection experiments and material from Norwegian cervids with this disease variant, researchers have also demonstrated that CWD prions can be experimentally transmitted from muscle tissue to mice.

A moose standing in a field.
New research shows that in sporadic CWD in moose and red deer, small amounts of prions are present in muscle, nerve, and lymphatic tissue—something that has not been shown before. Photo: Colourbox.

Previously, prions were not found outside the central nervous system in Norwegian red deer and moose with sporadic CWD. A new article from the Norwegian Veterinary Institute and Italian collaborators shows that, through infection experiments and a highly sensitive method (PMCA - protein misfolding cyclic amplification), prions can also be detected in tissues other than the brain and spinal cord in these species. This finding aligns with how other prion diseases behave, such as classical scrapie in small ruminants, classical CWD in North American cervid species, and sporadic prion diseases like Nor98/atypical scrapie in small ruminants and atypical bovine spongiform encephalopathy (BSE/mad cow disease) in cattle. Among animal prion diseases, only BSE in cattle has been transmitted to humans.
 

Examining Muscle, Nerve, and Lymph Node Tissue

In the study “Prions in Muscles of Cervids with Chronic Wasting Disease, Norway,” researchers examined muscle, nerve tissue, and lymph nodes from Norwegian reindeer (Rangifer tarandus), red deer, and moose. In contagious CWD, found in Norwegian wild reindeer, prions were expected to be widespread. In moose and red deer diagnosed with sporadic CWD based on brain tissue, prions had not previously been detected outside the central nervous system. This study changes that understanding, showing that small amounts of prions are present in muscle, nerve, and lymphatic tissue.
 

Prions Can Be Transmitted

Samples from moose also caused disease in laboratory mice after the infectious material was inoculated (directly introduced)into their brains. This experiment demonstrates that the disease can be transmitted, even though it is assumed that the sporadic type does not spread between living individuals. Such rodent experiments, known as bioassays, distinguish different prion strains.

The researchers emphasized that the study does not investigate the risk of transmission to humans and, therefore, does not change previous assessments that CWD is an animal disease. The only published study (Wadsworth et al., 2022) that examined Norwegian prion material using a human bioassay reported no transmission from moose or reindeer to a mouse model (genetically modified mice expressing the human prion protein, PrP).

–Our findings, including prion detection in muscle, might indicate potential exposure through consumption but do not provide insights into public health risks, says the study’s lead author, Tram Thu Vuong, a researcher at the Norwegian Veterinary Institute.  –Further studies are needed to understand these new CWD strains discovered in the Nordic region.

 –Findings like this highlight the importance of advancing knowledge when discovering new infectious agents and diseases. Furthermore, this is a signal to wildlife management that samples should be collected from dead or culled wildlife and that carcasses of animals with confirmed sporadic CWD should be removed from nature and destroyed, says Jørn Våge, researcher and CWD coordinator at the Norwegian Veterinary Institute.

The study “Prions in Muscles of Cervids with Chronic Wasting Disease, Norway” was funded by the Norwegian Veterinary Institute,  the Research Council of Norway, and the Italian Ministry of Health.

Chronic Wasting Disease (CWD)

Chronic Wasting Disease (CWD) is a prion disease, or transmissible spongiform encephalopathy, in cervids. This disease group also includes scrapie in sheep and goats, bovine spongiform encephalopathy (mad cow disease) in cattle, and Creutzfeldt-Jakob disease in humans. Prion diseases are characterized by accumulating misfolded prion proteins and gradual brain damage that leads to death.

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