Fameli, A, J. Edson, J.E. Banfield, C.S. Rosenberry, W.D. Walter. 2022. Variability in prion protein genotypes by spatial unit to inform susceptibility to chronic wasting disease. Prion 16 (1):254–264.
Chronic wasting disease (CWD) is a fatal, encephalopathy affecting North American cervids. Certain alleles in 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, a reintroduced population for which CWD cases have never been reported. We sequenced the prion protein gene (PRNP) of 565 elk samples collected over seven 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 H-W equilibrium in any of our sampling years (p-values between 0.14 and 1), consistent 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 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 repeating the process for different hunt zone delineations implemented in previous years. We interpolated these results to obtain a surface representing expected proportion of the less susceptible genotypes across the area. We found significant correlation between the results obtained for different hunt zone delineations (p-value<0.001), showing consistency in the pattern regardless of the hunt zone delineation used. 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 were adjacent to the deer Disease Management Area 3, where CWD has been present since 2014.