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United States Department of Agriculture

Agricultural Research Service

Research Project: TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES: THE ROLE OF GENETICS, STRAIN VARIATION, AND ENVIRONMENTAL CONTAMINATION IN DISEASE CONTROL

Location: Animal Diseases Research

Title: The role of genetics in chronic wasting disease of North American cervids

Authors
item Robinson, S -
item Samuel, M -
item O'Rourke, Katherine
item Johnson, C -

Submitted to: Prion
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 2012
Publication Date: April 1, 2012
Citation: Robinson, S.J., Samuel, M.D., Orourke, K.I., Johnson, C.J. 2012. The role of genetics in chronic wasting disease of North American cervids. Prion. 6(2):153-162.

Interpretive Summary: Chronic wasting disease (CWD) is an important management issue for many North American cervid populations. This fatal prion disease has led to deer population declines in areas with high infection rates and to economic losses even in low-prevalence areas. CWD is a prion disease caused by the abnormal form of a prion protein which is encoded by the prion protein gene (PRNP). Variations among host species of cervids and genotypes can lead to different prion forms that moderate individual susceptibility to CWD. PRNP genes have been sequenced in several cervid species known to be susceptible to CWD (elk, mule deer, white-tailed deer, moose.) and species for which susceptibility is not yet determined (caribou and sika deer). A limited number of variations in PRNP genetics have been associated with reduced susceptibility to CWD infection and slower progression to clinical signs. Here we review the body of research on PRNP genetics of North American cervids with emphasis on known polymorphisms in the PRNP gene, observed genotypic differences in CWD infectivity and progression, host and agent mechanisms for disease resistance, and potential for natural selection for CWD-resistance. We also identify important knowledge gaps that need to be addressed by future research. This review is particularly relevant to understanding the epidemiology of free-ranging cervids, for potential selective breeding for CWD resistance in captive cervids, and to agriculture through potential cross-species transmission of CWD to domestic animals.

Technical Abstract: Chronic wasting disease (CWD) is an important management issue for many North American cervid populations. This fatal prion disease has led to deer population declines in areas with high infection rates and to economic loses even in low-prevalence areas. Because potential for cross-species transmission is largely unknown, fears for potential cross-over into livestock or human populations remain. Research has clearly established that the prion protein gene (PRNP) encodes the protein responsible for transmissible spongiform ecephelopathies (TSEs) including CWD. Polymorphisms in the PRNP gene can lead to different prion forms that moderate individual susceptibility and tolerance to TSE infection; however, none of the known PRNP genotypes in cervids are completely resistant to infection. PRNP genes have been sequenced in several cervid species including elk, mule deer, white-tailed deer, moose; which are known to be infected by CWD, as well as caribou, fallow deer and sika deer, for which susceptibility is not yet determined. With thousands of sequences examined, the PRNP gene is remarkably conserved within the family Cervidae; fewer than 20 amino acid polymorphisms occur within the 256 amino acid third exon. Some of these polymorphisms have been associated with lower rates of CWD infection and slower progression to clinical CWD. Here we review the body of research on PRNP genetics of North American cervids with emphasis on known polymorphisms in the PRNP gene, observed genotypic differences in CWD infectivity and progression, host and agent mechanisms for disease resistance, and potential for natural selection for CWD-resistance. We also identify important knowledge gaps that need to be addressed by future research.

Last Modified: 8/27/2014
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