Abstract
Analysis of the PRNP gene in cervids naturally infected with chronic wasting disease (CWD) suggested that PRNP polymorphisms affect the susceptibility of deer to infection. To test this effect, we orally inoculated 12 white-tailed deer with CWD agent. Three different PRNP alleles, wild-type (wt; glutamine at amino acid 95 and glycine at 96), Q95H (glutamine to histidine at amino acid position 95) and G96S (glycine to serine at position 96) were represented in the study cohort with 5 wt/wt, 3 wt/G96S, and 1 each wt/Q95H and Q95H/G96S. Two animals were lost to follow-up due to intercurrent disease. The inoculum was prepared from Wisconsin hunter-harvested homozygous wt/wt animals. All infected deer presented with clinical signs of CWD; the orally infected wt/wt had an average survival period of 693 days post inoculation (dpi) and G96S/wt deer had an average survival period of 956 dpi. The Q95H/wt and Q95H/G96S deer succumbed to CWD at 1,508 and 1,596 dpi respectively. These data show that polymorphisms in the PRNP gene affect CWD incubation period. Deer heterozygous for the PRNP alleles had extended incubation periods with the Q95H allele having the greatest effect.
Highlights
Chronic wasting disease (CWD) is a prion disease affecting Cervidae
All deer were obtained as fawns from northern Wisconsin, a region with no cases of CWD as determined by extensive statewide sampling performed by the Wisconsin Department of Natural Resources
The deer in this study had PRNP alleles that were variable at amino acids (AA) 95 and 96 with the most common allele (17/24) having glutamine at position 95 and glycine at position 96, referred to as wild-type
Summary
Chronic wasting disease (CWD) is a prion disease affecting Cervidae. CWD is pandemic in both domestic and wild deer. The geographic distribution of CWD has increased, spreading from Colorado and Wyoming across North America. In areas where CWD has become endemic, disease incidence continues to rise. CWD agent persists in an infectious form in the environment. Cohabitation of contaminated regions with disease-naıve Cervidae, as well as susceptible species such as ovines, bovines and wild rodents, could extend the impact of CWD. Since cervids are the predominant game and subsistence species for meat, the risk of CWD transmission to humans cannot be ruled out. Unlike Bovine Spongiform Encephalopathy (Mad Cow disease), CWD is contagious and can spread horizontally through contaminated environments. The susceptibility of the host species is of great concern to the expansion of the epidemic as well as to the accumulation of infectivity in the environment
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