2007 Annual Report
1a.Objectives (from AD-416)
Obj. 1. Assess the cross species transmissibility of transmissible spongiform encephalopathies (TSEs) in livestock and wildlife.
Obj. 2. Investigate the pathobiology of TSEs in natural and secondary hosts.
Obj. 3. Investigate pathogenesis and ante mortem detection of bovine spongiform encephalopathy (BSE).
Obj. 4. Develop a method to detect central nervous system (CNS) tissue contamination on carcasses.
1b.Approach (from AD-416)
Studies are focused on the four animal Transmissible Spongiform Encephalopathy (TSE) agents found in the United States: bovine spongiform encephalopathy (BSE); scrapie of sheep and goats; chronic wasting disease (CWD) of deer, elk, and moose; and transmissible mink encephalopathy (TME). These agents will be tested for cross-species transmissibility into various livestock and cervid species using both oral and intracerebral inoculation. Sites of accumulation, routes of infection, methods of isolate differentiation, and in the case of BSE, genetics of susceptibility and ante-mortem diagnostics, will be investigated. Existing technology developed at the National Animal Disease Center and those used in the meat packing industry for the detection of fecal contamination on carcasses will be adapted to detect CNS tissue contamination on carcasses.
Title: Prion protein knock-out cattle
Problem: The role of the prion protein in prion diseases in genetically modified livestock species has not been analyzed yet.
Activity: Prion protein gene knock-out cattle were produced in collaboration with Hematech Inc. These animals are healthy up to an age of 28 months and brain material from knock-out cattle was not able to support BSE amplification using an in vitro PrP**Sc amplification technique.
Impact: These animals are useful to study the role of the bovine prion protein in the pathogenesis of cattle prion diseases and could provide a prion-free source of bovine products for the biomedical industry.
Title: CWD transmission to fallow deer.
Problem: CWD has never been reported in wild or captive fallow deer.
Activity: To determine the transmissibility of chronic wasting disease (CWD) to fallow deer and to provide information about clinicopathological features of the disease in fallow deer, fawns were inoculated intracerebrally with CWD brain suspension from elk and white-tailed deer. Five animals were found to amplify CWD PrP**d from mule deer and elk in absence of spongiform lesions between 2 and 3 years post inoculation. Four years after the CWD inoculation, the remaining five CWD inoculated fallow deer are alive and healthy. Although these preliminary findings demonstrate that it is possible to transmit CWD to fallow deer by intracerebral inoculation, they indicate a low probability for oral transmission of CWD to this deer species.
Impact: This study provides important information for the alternative livestock industry and wildlife agencies.
Title: PrP**d-detection in paraffin-embedded tissue
Problem: CNS tissues from animals positive for PrP**d by IHC are often only available as paraffin-embedded tissues.
Activity: A Western blot method for the detection of PrP**d in CNS-tissues from scrapie-infected sheep which were formalin-fixed and paraffin-embedded was developed.
Impact: These studies will help other researchers and regulatory agencies to obtain additional scientific information from formalin fixed, paraffin-embedded tissues when frozen tissues are not available.
Title: Rumen fluid effects on PrP**d levels
Problem: A fully functioning rumen had been postulated to lower the risk to TSE disease in adult animals.
Activity: Work on this topic revealed that rumen fluid does not degrade PrP**d from sheep scrapie.
Impact: These studies provide evidence that active rumen fermentation (and age of the animal) is unlikely to influence TSE disease risk. This information is critical for scientists studying the pathogenesis and epidemiology of TSEs.
The research implements the following research components in the 2006-2011 Animal Health National Program (NP 103) Action Plan:.
1)Genetic and biological determinants of disease susceptibility, and.
2)Countermeasures to prevent and control transmissible spongiform encephalopathies. The research addresses Agency Performance Measure 3.2.1 (Provide scientific information to protect animals from pests, infectious diseases, and other disease causing entities that affect animal and human health). Target: Increase the delivery of dependable high quality scientific information to customers, stakeholders, and partners. New discoveries and technologies will be effectively communicated to improve the management of diseases that affect the livestock and poultry industries, and which may affect public health. Effective communication will be achieved by publishing in highly regarded scientific journals and trade publications and on the internet and through presentations at industry meetings. The research also addresses Agency Performance Measure 3.2.3 (Develop and transfer tools to the agricultural community, commercial partners, and Federal agencies to control or eradicate domestic and exotic diseases that affect animal and human health). Target: Develop diagnostic and preventative tools to control and/or eradicate domestic diseases that affect production, trade, and public health. Provide action agencies with data to support risk analyses to assess the impact of domestic and exotic diseases and develop control and eradication strategies.
5.Significant Activities that Support Special Target Populations
|Number of new CRADAs and MTAs||1|
|Number of active CRADAs and MTAs||2|
|Number of patent applications filed||1|
|Number of non-peer reviewed presentations and proceedings||6|
|Number of newspaper articles and other presentations for non-science audiences||1|
Hamir, A.N., Miller, J.M., Kunkle, R.A., Hall, S.M., Richt, J.A. 2007. Susceptibility of cattle to first-passage intracerebral inoculation with chronic wasting disease agent from white-tailed deer. Veterinary Pathology. 44:487-493.
Nicholson, E.M., Richt, J.A., Rasmussen, M.A., Hamir, A.N., Lebepe-Mazur, S, Horst, R.L. 2007. Exposure of sheep scrapie brain homogenate to rumen-simulating conditions does not result in a reduction of PrP**sc levels. Letters in Applied Microbiology. 44:631-636.
Richt, J.A., Kasinathan, P., Hamir, A.N., Castilla, J., Sathiyaseelan, T., Vargas, F., Sathiyaseelan, J., Wu, H., Matsushita, H., Koster, J., Kato, S., Ishida, I., Soto, C., Robl, J.M., Kuroiwa, Y. 2007. Production of cattle lacking prion protein. Nature Biotechnology. 25(1):132-138.
Richt, J.A., Kunkle, R.A., Alt, D., Nicholson, E.M., Hamir, A.N., Czub, S., Kluge, J., Davis, A.J., Hall, S.M. 2007. Identification and characterization of two bovine spongiform encephalopathy cases diagnosed in the United States. Journal of Veterinary Diagnostic Investigation. 19(2):142-154.