TRANSMISSION, DIFFERENTIATION, AND PATHOBIOLOGY OF TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES
Location: Virus and Prion Research Unit
Title: Pathobiology and diagnosis of animal transmissible spongiform encephalopathies: current knowledge, research gaps, and opportunities
Submitted to: Government Publication/Report
Publication Type: Government Publication
Publication Acceptance Date: May 1, 2007
Publication Date: July 1, 2007
Citation: Kehrli, Jr., M.E., O'Rourke, K.I., Hamir, A.N., Richt, J.A., Nicholson, E.M., Silva, C.J., Edelman, D., Gay, C.G. 2007. Pathobiology and diagnosis of animal transmissible spongiform encephalopathies: current knowledge, research gaps, and opportunities [government white paper]. Beltsville, MD: Interagency Working Group on Prion Science, Subcommittee on Pathobiology and Diagnostics. USDA, Agriculture Research Service. 33 p.
Transmissible spongiform encephalopathies (TSEs) are fatal neurologic diseases that can affect several animal species and human beings. There are four animal TSE agents found in the United States: scrapie of sheep and goats; chronic wasting disease (CWD) of deer, elk, and moose; transmissible mink encephalopathy (TME) and bovine spongiform encephalopathy (BSE). Although the animal TSEs do not cause major death losses among US livestock populations, they are important because of international trade issues. The experience of the United Kingdom and Europe in dealing with the vast majority of the world's BSE cases, serves as a reminder of the need for continuing vigilance in monitoring risks for public health and research to answer remaining questions around the pathogenesis and transmission of these diseases. There remain questions on 1) cross-species transmissibility of TSEs in livestock and wildlife; 2) the pathobiology of TSEs in natural and secondary hosts; pathogenesis and transmission of CWD; and 4) pathogenesis and ante mortem detection of typical and atypical BSE. Our understanding of the pathogenesis and transmission of these diseases continues to evolve as ongoing, global TSE research efforts focus on defining tissue sites of abnormal prion accumulation, routes of infection, methods of strain differentiation, genetics of susceptibility and ante-mortem diagnostics. In this paper, a Subcommittee on Pathobiology and Diagnostics of TSEs for an Interagency Working Group on Prion Science summarizes the science of animal TSEs in order to identify knowledge gaps for the purpose of prioritizing animal prion research needs. Because of substantial losses involving international trade and potential risk for interspecies transmission to susceptible livestock and possibly humans, the presence of BSE, CWD, scrapie and TME in the United States presents a liability to U.S. domestic and alternative livestock industries. In addition, the proven risk of BSE to agriculture and public health from subclinical or clinically sick animals requires science-based surveillance for any silent, unrecognized epizootic expansions of these diseases in populations of animals that could either directly or indirectly affect food animals. CWD is an example of an uncontrolled expanding epidemic that threatens not only cervids but possibly other livestock. CWD also has elicited public health surveillance programs to monitor for scientific evidence of a prion disease in humans that consume venison. Therefore, some of the research needs are precautionary, but the risks to animal and human health from being caught unaware are high. Efforts are being made by both federal and state regulatory agencies to eradicate scrapie and CWD, and to determine the prevalence of BSE. The effectiveness of these programs will depend heavily on having accurate information about the nature of these diseases, not only in the original hosts, but also in other species that may be in contact with infected animals.