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From: TSS ()
Subject: BSE, BOVINE - USA: ATYPICAL STRAIN
Date: June 1, 2006 at 11:09 am PST

BSE, BOVINE - USA: ATYPICAL STRAIN
**********************************
A ProMED-mail post

ProMED-mail, a program of the
International Society for Infectious Diseases

Date: 31 May 2006
From: Terry S. Singletary and Mary Marshall

Source: Rapid City Journal [edited]


The 2 cases of bovine spongiform encephalopathy found in U.S. cattle
over the past year came from a rare strain of BSE found largely in
Europe that scientists are only beginning to identify, according to
research by a French scientist.

Researchers in France and Italy who presented their work at an
international conference in London reported 2 rare strains of bovine
spongiform encephalopathy that are harder to detect and affect mainly
older cattle.

Thierry Baron of the French Food Safety Agency presented research
indicating that a 12-year-old Texas cow testing positive for BSE in
June 2005, and the 10-year-old Alabama cow that tested positive in
March [2006?], showed identical testing patterns to a small number of
BSE cases in France, Sweden and Poland.

Animal scientists are calling such strains "atypical" BSE, which is
different from the "typical" BSE caused by cattle eating feed with
ruminant offal contaminated with a BSE protein.

They don't know whether the atypical strains are caused by something
else or simply appear spontaneously in older, susceptible cattle.

Art Davis, a U.S. Department of Agriculture (USDA) scientist for the
Animal and Plant Health Inspection Service (APHIS) at the National
Veterinary Services Laboratory in Ames, Iowa, said in his
presentation Sunday at the London conference that the Texas and
Alabama test results showed completely different prion patterns than
the Washington state case discovered in December 2003.

"The classical lesions were not there," Davis said of the cases. The
Washington state cow originated in Alberta, Canada, near where
several other BSE cases have been found.

The "typical" BSE strain caused a mad cow disease epidemic in Great
Britain beginning in the mid-1980s that killed 184 000 cattle and
more than 100 people who contracted a human form of the disease
caused by eating contaminated beef products.

The scientific evidence shows that in almost all cattle cases, the
fatal neurological disorder was contracted through contaminated meat
and bone meal fed to the cow, typically at a young age.

However, scientists finding atypical cases of BSE are beginning to
question if there has been a change in the abnormal protein that
causes BSE or if cattle might be susceptible to a sporadic BSE
affecting older cattle.

Danny Matthews, head of transmissible spongiform encephalopathies at
England's Veterinary Laboratories Agency, said recent research on
atypical cases of BSE raises questions over whether older cattle can
sporadically get the disease or if there are more strains of BSE than
previously understood. Scientists might also be facing something new,
such as "son of BSE," he said.

"We don't fully understand what atypical BSE means," Matthews said.
"Is it spontaneous or another source causing it? Time will tell."

Although the test patterns in the U.S. cases and atypical cases in
Europe closely matched, Baron said there were no known links among
any of the positive animals. The French Food Safety Agency sent a
researcher to the United States to study the positive Texas case and
compare its results to known cases in France that did not match the
typical BSE positive tests.

"You could place them side-by-side and not tell the difference," Baron said.

Baron also raised the prospect that the disease could be sporadic in
at least a small number of older cattle. He said, however, such a
conclusion would be hard to determine because of the small number of
cattle with this atypical strain globally.

Dr. Sam Holland, South Dakota's state veterinarian, said there are
many strains of BSE and varying degrees of infectiousness of the
agent.

"What if the scenario is there is an atypical prion out there that is
much less infective, has a longer incubation period and has not been
recognized as part of the Great Britain BSE experience identified in
1985 and '86?" Holland said. "There could be others out there that we
haven't recognized yet."

He said it is possible the atypical strains are not caused by
contaminated feed and that it still makes sense to continue the ban
on ruminant offal in cattle feed to prevent the spread of typical BSE
and eventually to eliminate that disease.

"Based on what we know about BSE, it makes good sense to -- number
one -- keep some surveillance in place; number 2, watch what we
import and restrict shipments and movements from places that have had
those syndromes; and, number 3, with what we know about BSE, it seems
to be very prudent to keep our ruminant offal ban in place," Holland
said.

"At least for typical BSE's, it seems to be very effective. It's
probably reasonable to continue the ruminant offal ban even after the
last typical BSE case has been eliminated."

Editor's note: DTN, a private company based in Omaha, Neb., provides
information to agriculture, energy trading markets and other
weather-sensitive industries. The Rapid City Journal received a copy
of DTN's story and expanded on it.

[Byline: Chris Clayton]

--
Terry S. Singletary
and
Mary Marshall

[An atypical form has been found in sheep with scrapie. Other
countries have indicated an atypical form of BSE. It seems logical
that the US would have an a atypical form as well. The case might
even be made that new variant CJD is an atypical form of CJD. Clearly
there is more to the TSE diseases than we fully comprehend. - Mod.TG]

[see also:
2005
----
Scrapie, atypical, ovine - Falkland Islands 20051120.3371
2004
----
Scrapie, atypical, sheep - UK and Ireland 20041210.3274
Scrapie, atypical, sheep - UK (02) 20040409.0965
Scrapie, atypical, sheep - UK20040408.0952
BSE, atypical - France: OIE 20040201.0391
Scrapie, atypical, sheep - France: OIE 20040201.0390
BSE - France: distinct molecular phenotypes 20040107.0076
2003
----
Scrapie - Norway: new phenotype 20031117.2857
BSE - Japan (08): 9th case, lab findings 20031115.2838
BSE, atypical case - Italy: OIE 20031022.2649
BSE - Italy: atypical, suspected 20031012.2576
BSE - Japan (06): atypical 20031009.2547
BSE - Japan (05): atypical 20031008.2526
BSE - Japan (04): atypical 20031007.2511
2002
----
BSE? Sheep - USA (Vermont) 20020412.3937
2000
----
BSE? sheep - USA (Vermont) (06) 20000724.1223
BSE? sheep - USA (Vermont) 20000717.1184
1996
----
CJD sporadic vs variant differences 19960526.0990]
...............tg/pg/lm


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