TRANSMISSION, DIFFERENTIATION, AND PATHOBIOLOGY OF TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES
Location: Virus and Prion Research Unit
Title: Experimental Interspecies Transmission Studies of the Transmissible Spongiform Encephalopathies to Cattle: Comparison to Bovine Spongiform Encephalopathy in Cattle
Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Review Article
Publication Acceptance Date: December 17, 2011
Publication Date: May 1, 2011
Citation: Hamir, A.N., Kehrli, Jr., M.E., Kunkle, R.A., Greenlee, J.J., Nicholson, E.M., Richt, J.A., Miller, J.M., Cutlip, R.C. 2011. Experimental interspecies transmission studies of the transmissible spongiform encephalopathies to cattle: comparison to bovine spongiform encephalopathy in cattle. Journal of Veterinary Diagnostic Investigation. 23(3):407-420.
Prion diseases or transmissible spongiform encephalopathies (TSEs) of animals include scrapie of sheep and goats; transmissible mink encephalopathy (TME); chronic wasting disease (CWD) of deer, elk and moose; and bovine spongiform encephalopathy (BSE) of cattle. Since the emergence of BSE and its presumed spread to humans in the form of variant Creutzfeldt-Jakob disease (vCJD) there has been interest in susceptibility of cattle to CWD and scrapie. Experimental cross-species transmission of TSE agents provides valuable information for potential host ranges of known TSEs. TSEs in natural hosts are characterized by long incubation times, therefore, cross-species transmission studies take years to complete. Some interspecies transmission studies have been conducted by inoculating infectious prions intracerebrally (IC) into the brain rather than orally; the latter is generally effective in intraspecies transmission studies and is considered a natural route by which animals acquire TSEs. A "species barrier" for a TSE agent, reflects results of unsuccessful interspecies oral transmission attempts. IC inoculation requires smaller dosage volumes of inoculum, and typically results in higher attack rates and reduces incubation time compared to oral transmission. If a species is found resistant to a TSE agent by IC inoculation, then potential for successful oral transmission is considered negligible. This review summarizes TSE interspecies transmission studies conducted in cattle and compares findings to BSE in cattle. To date, results indicate that cattle are susceptible to IC inoculation of TME and develop lesions similar to BSE. However, cattle are not susceptible to the oral transmission of scrapie or CWD, and when these agents are inoculated by the IC route, cattle do not develop neuropathology that resembles BSE or TME.