ARS | Publication request: Experimental Inoculation of Spiroplasma mirum and Transmissible Mink Encephalopathy (TME) into Raccoons (Procyon lotor)

Submitted to: Canadian Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 11, 2010
Publication Date: January 1, 2011
Citation: Hamir, A.N., Greenlee, J.J., Stanton, T.B., Smith, J.D., Doucette, S., Kunkle, R.A., Stasko, J.A., Richt, J.A., Kehrli, Jr., M.E. 2011. Experimental inoculation of raccoons (Procyon lotor) with Spiroplasma mirum and transmissible mink encephalopathy (TME). Canadian Journal of Veterinary Research. 75(1):18–24.

Interpretive Summary: Others have claimed that a certain bacteria (Spiroplasma mirum) is capable of producing lesions of spongiform encephalopathy. To test this claim we used a raccoon model of spongiform encephalopathy, 5 groups of raccoon kits were inoculated surgically directly into the brain with either the bacteria and/or transmissible mink encephalopathy (TME). Two other groups of raccoon kits served as controls. All animals inoculated with TME (either alone or in combination with Spiroplasma) showed clinical signs of neurologic disorder and were euthanized within 6 months post inoculation. Spongiform encephalopathy was observed by light microscopy and the presence of prion protein in only the raccoons administered TME. Bacteria-inoculated raccoons not administered TME agent, were euthanized at 30 MPI. They did not show clinical neurologic signs, their brains did not have lesions of spongiform encephalopathy and their tissues were negative for the bacteria. Results of this study indicate that Spiroplasma mirum does not induce TSE-like disease in raccoons.

Technical Abstract: To determine if Spiroplasma mirum would be capable of producing lesions of spongiform encephalopathy in raccoons (Procyon lotor), 5 groups (n = 5) of raccoon kits were inoculated intracerebrally with either S. mirum and/or transmissible mink encephalopathy (TME). Two other groups (n = 5) of raccoon kits served as sham-inoculated controls. All animals inoculated with TME (either alone or in combination) showed clinical signs of neurologic disorder and were euthanized within 6 months post inoculation (MPI). None of the carcasses revealed gross lesions. Spongiform encephalopathy was observed by light microscopy and the presence of abnormal disease causing prion protein (PrP**d) was detected by immunohistochemistry (IHC) and Western blot (WB) techniques in only the raccoons administered TME. Spiroplasma-inoculated raccoons not administered TME agent, were euthanized at 30 MPI. They did not show clinical neurologic signs, their brains did not have lesions of spongiform encephalopathy and their tissues were negative for Spiroplasma mirum by PCR and for PrP**d by IHC and WB techniques. Results of this study indicate that Spiroplasma mirum does not induce TSE-like disease in raccoons.