ARS | Publication request: Comparison of Transmissible Mink Encephalopathy Isolates in Raccoons

Submitted to: American College of Veterinary Pathologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 30, 2010
Publication Date: October 30, 2010
Citation: Smith, J.D., Greenlee, J.J., Hamir, A.N. 2010. Comparison of transmissible mink encephalopathy isolates in raccoons [abstract]. American College of Veterinary Pathologists. Paper No. 145.

Technical Abstract: Owing to its susceptibility to various transmissible spongiform encephalopathies (TSE) and relatively short incubation times, the raccoon (Procyon lotor) has been suggested as a model for TSE strain differentiation. Transmissible mink encephalopathy (TME) is a prion disease of undetermined origin initially identified in North American ranch-raised mink. Raccoons are susceptible to TME derived from mink, but the susceptibility of this species to additional TME isolates is unknown. The objective of this study was to investigate the susceptibility of raccoons to various TME isolates and compare clinicopathologic and immunoassay data. Raccoon kits were inoculated intracerebrally with raccoon-passaged TME (racTME), bovine-passaged TME (bovTME), or hamster-adapted "drowsy" (DY) and "hyper" (HY) strains of TME. Raccoons inoculated with racTME or bovTME developed neurologic signs and were euthanized on average 6.6 months post-inoculation for each group. The distribution of spongiform encephalopathy lesions (SE) and abnormal prion protein (PrP**res) were similar between groups. The most severe SE lesions were identified in the cerebral cortex with sparing of the cerebellum. PrP**res-immunoreactivity was similarly distributed throughout the CNS, and both groups were positive for PrP**res via Western blot. In contrast, raccoons inoculated with DY or HY TME did not develop clinical signs and were negative for SE and PrP**res when examined histologically and via immunohistochemistry and/or Western blot, respectively. The results of this study indicate raccoons are susceptible to infection with bovine-passaged TME, but not hamster-adapted DY and HY strains. RacTME and bovTME exhibited similar clinicopathologic and immunohistochemical characteristics, suggesting a commonality in the TME isolates or host response to the agent.