Prion protein polymorphisms in Michigan white-tailed deer (Odocoileus virginianus)

Chronic Wasting Disease (CWD), a well-described transmissible spongiform encephalopathy of the Cervidae family, is associated with the aggregation of an abnormal isoform (PrP^CWD) of the naturally occurring host prion protein (PrP^C). Variations in the PrP gene (PRNP) have been associated with CWD rate of infection and disease progression. We analysed 568 free-ranging white-tailed deer (Odocoileus virginianus) from 9 CWD-positive Michigan counties for PRNP polymorphisms. Sampling included 185 CWD-positive, 332 CWD non-detected, and an additional 51 CWD non-detected paired to CWD-positives by sex, age, and harvest location. We found 12 polymorphic sites of which 5 were non-synonymous and resulted in a change in amino acid composition. Thirteen haplotypes were predicted, of which 11 have previously been described. Using logistic regression, consistent with other studies, we found haplotypes C (OR = 0.488, 95% CI = 0.321-0.730, P < 0.001) and F (OR = 0.122, 95% CI = 0.007-0.612, P < 0.05) and diplotype BC (OR = 0.340, 95% CI = 0.154-0.709, P < 0.01) were less likely to be found in deer infected with CWD. As has also been documented in other studies, the presence of a serine at amino acid 96 was less likely to be found in deer infected with CWD (P < 0.001, OR = 0.360 and 95% CI = 0.227-0.556). Identification of PRNP polymorphisms associated with reduced vulnerability to CWD in Michigan deer and their spatial distribution can help managers design surveillance programmesand identify and prioritize areas for CWD management.