<i>PRNP</i> variant frequencies in Roosevelt and Rocky Mountain elk ( <i>Cervus canadensis</i> ) from Oregon and their implications for chronic wasting disease

Chronic wasting disease (CWD) is a fatal disease in cervids caused by abnormally folded proteins known as prions. Since its identification in 1967, CWD has spread to wild cervid populations in 36 U.S. states. Some variants in the prion protein gene (PRNP) are known to confer advantages against prion diseases in many species including cervids. In elk (Cervus canadensis), a non-synonymous mutation in PRNP is associated with CWD susceptibility and/or progression. PRNP codon 132L, which encodes leucine rather than methionine (132M), is relatively less frequent among CWD positive elk than among CWD negative elk. In 2021, CWD was detected in Idaho near the Oregon border, heightening concerns about potential spread into Oregon's cervid populations. We therefore sequenced the complete coding region of PRNP in 183 elk collected across their range in Oregon, to assess PRNP variation. PRNP sequences have not previously been examined in the Roosevelt elk (C. c. roosevelti) subspecies. We assessed 101 Roosevelt elk in western Oregon, finding that 42% carried at least one copy of 132L. Among Rocky Mountain elk (n = 82; C. c. nelsoni) in Oregon, 49% carried at least one copy of the advantageous allele 132L. Oregon elk carry a relatively high proportion of 132L compared to previously examined elk populations nationwide. Despite this high frequency, Oregon elk populations remain at substantial risk from CWD. These findings can inform management strategies aimed at mitigating CWD risk in Oregon's cervid populations.