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From: TSS ()
Subject: Spiroplasma spp. from transmissible spongiform encephalopathy brains or ticks induce spongiform encephalopathy in ruminants
Date: October 5, 2007 at 11:18 am PST

Spiroplasma spp. from transmissible spongiform encephalopathy brains or ticks induce spongiform encephalopathy in ruminants

Frank O. Bastian,1 Dearl E. Sanders,2 Will A. Forbes,2 Sue D. Hagius,1

Joel V. Walker,1 William G. Henk,3 Fred M. Enright1 and Philip H. Elzer1
Frank O. Bastian

1Department of Veterinary Science, Louisiana State University Agricultural Center,
111 Dalrymple Building, Baton Rouge, LA 70803, USA
2Idlewild Research Station, Louisiana State University Agricultural Center, Baton Rouge, LA 70803,
3Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary
Medicine, Baton Rouge, LA, USA
Received 10 January 2007
Accepted 19 April 2007

Spiroplasma, small motile wall-less bacteria, are linked by molecular and serological studies to the
transmissible spongiform encephalopathies (TSEs), which include scrapie in sheep, chronic
wasting disease (CWD) in deer and Creutzfeldt–Jakob disease in humans. In this study, two
experiments were undertaken to determine the role of spiroplasma in the pathogenesis of TSE. In
experiment 1, Spiroplasma mirum, a rabbit tick isolate that had previously been shown to
experimentally induce spongiform encephalopathy in rodents, was inoculated intracranially (IC)
into ruminants. S. mirum-inoculated deer manifested clinical signs of TSE after 1.5 to 5.5 months
incubation. The deer, as well as sheep and goats, inoculated with S. mirum developed spongiform
encephalopathy in a dose-dependent manner. In experiment 2, spiroplasma closely related to
S. mirum were isolated from TSE-affected brains via passage in embryonated eggs, and
propagated in cell-free M1D media. Spiroplasma spp. isolates from scrapie-affected sheep brain
and from CWD-affected deer brain inoculated IC into sheep and goats induced spongiform
encephalopathy closely resembling natural TSE in these animals. These data show spiroplasma to
be consistently associated with TSE, and able experimentally to cause TSE in ruminant animal
models, therein questioning the validity of studies that have concluded the prion, a miss-folded
protease-resistant protein that builds up in TSE brains during the course of the disease, to be the
sole causal agent. The spiroplasma infection models reported here will be important for
investigating factors involved in the pathogenesis of TSE since ruminants are the natural hosts.


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