Variability in prion protein genotypes by spatial unit to inform susceptibility to chronic wasting disease

ABSTRACT

Chronic wasting disease (CWD) is a fatal encephalopathy affecting North American cervids. Certain alleles in a host’s prion protein gene are responsible for reduced susceptibility to CWD. We assessed for the first time variability in the prion protein gene of elk (Cervus canadensis) present in Pennsylvania, United States of America, a reintroduced population for which CWD cases have never been reported. We sequenced the prion protein gene (PRNP) of 565 elk samples collected over 7 years (2014–2020) and found two polymorphic sites (codon 21 and codon 132). The allele associated with reduced susceptibility to CWD is present in the population, and there was no evidence of deviations from Hardy-Weinberg equilibrium in any of our sampling years (p-values between 0.14 and 1), consistent with the lack of selective pressure on the PRNP. The less susceptible genotypes were found in a frequency similar to the ones reported for elk populations in the states of Wyoming and South Dakota before CWD was detected. We calculated the proportion of less susceptible genotypes in each hunt zone in Pennsylvania as a proxy for their vulnerability to the establishment of CWD, and interpolated these results to obtain a surface representing expected proportion of the less susceptible genotypes across the area. Based on this analysis, hunt zones located in the southern part of our study area have a low proportion of less susceptible genotypes, which is discouraging for elk persistence in Pennsylvania given that these hunt zones are adjacent to the deer Disease Management Area 3, where CWD has been present since 2014.

KEYWORDS:

• Chronic wasting disease
• prion protein gene
• elk
• genetic variability
• spatial variability

Acknowledgments

The authors would like to thank Avery Corondi and hunters from Pennsylvania who submitted samples to the PGC. We also thank Editor-in-Chief Dr. Yury Chernoff and two anonymous reviewers for their valuable contributions to this article. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Financial support was provided by the Pennsylvania Game Commission.