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From: TSS (216-119-132-57.ipset12.wt.net)
Subject: Experimental Transmission of Chronic Wasting Disease Agent to Cattle by Intracerebral Route: Final Outcome of the Study Authors
Date: November 7, 2004 at 6:48 pm PST

-------- Original Message --------
Subject: Experimental Transmission of Chronic Wasting Disease Agent to Cattle by Intracerebral Route: Final Outcome of the Study Authors
Date: Sun, 07 Nov 2004 20:45:50 -0600
From: "Terry S. Singeltary Sr."
To: BSE-L
CC: CJDVOICE@YAHOOGROUPS.COM

Research

Research >

Title: Experimental Transmission of Chronic Wasting Disease Agent to
Cattle by Intracerebral Route: Final Outcome of the Study Authors
item Hamir, Amirali

item Kunkle, Robert - bob

item Richt, Juergen

item Cutlip, Randall - ARS RETIRED
item Miller, Janice - ARS RETIRED
item O'Rourke, Katherine

item Williams, Elizabeth - UNIVERSITY OF WYOMING
item Miller, M - COLORADO DIV WILDLIFE
item Stack, Mick - VLA-WEYBRIDGE, UK
item Chaplin, Melanie - VLA-WEYBRIDGE, UK

Submitted to: Meeting Abstract
Publication Acceptance Date: September 29, 2004
Publication Date: N/A
Publisher's URL: http://www.ustse2004.com/
Technical Abstract: Thirteen calves were inoculated intracerebrally with
brain suspension from mule deer naturally affected with CWD. Three other
calves were kept as uninoculated controls. The experiment was terminated
at 6 years post inoculation (PI). During that time, prion protein
(PrPres) was found in the central nervous system (CNS) of 5 cattle. None
of these animals had shown any specific clinical signs that were common
to all. Microscopic lesions suggestive of spongiform encephalopathy in
the brains of these PrPres positive animals were subtle in the first 3
and absent in the latter 2 cases. However, all 5 animals were positive
for PrPres by both immunohistochemistry and Western blot. The 3
uninoculated control cattle and 8 other inoculated animals euthanized
during this time did not have PrPres in their CNS. Degenerative changes
indicative of neuroaxonal dystrophy (NAD) were seen in dorsal medulla
oblongata and appeared to be related to advancing age in both inoculated
and control cattle. Analysis of the gene encoding bovine PRNP revealed
similar findings, i.e., homozygosity for alleles encoding 6 octapeptide
repeats, serine (S) at codon 46 and S at codon 146 in all samples.
Findings of this study show that although PrPres amplification occurred
following direct inoculation into the brain, none of the affected
animals had classical histopathological lesions of spongiform
encephalopathy. Furthermore, only 38% of the inoculated cattle
demonstrated amplification of PrPres. Although intracerebral inoculation
is an unnatural route of exposure, and is the most severe challenge
possible, this experiment shows that CWD transmission in cattle can have
long incubation periods (up to 5 years). This finding suggests that oral
inoculation of cattle with CWD may not result in amplification of PrPres
within CNS tissues during the normal lifespan of cattle. It is possible
that a second bovine passage of material (brain infected with CWDmd)
from this study may result in a larger proportion of affected cattle
with a shortened incubation time, and may produce different clinical and
pathological findings. Such a study is now in progress. Also,
experimental inoculations of cattle with CWD isolates from white-tailed
deer and elk are needed to compare clinicopathological findings with the
present study and these studies will be initiated in the near future.


http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=167759tss






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