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[SANET-MG] mad cow testing in USA
The New York Times
June 25, 2005
Testing Changes Ordered After U.S. Mad Cow Case
By DONALD G. McNEIL Jr.
Substantial changes in the nation's mad cow testing system were ordered
yesterday after British tests on a cow slaughtered in November confirmed
that it had the disease even though the American "gold standard" test
said it did not.
"The protocol we developed just a few years ago to conduct the tests
might not be the best option today," Agriculture Secretary Mike Johanns
said in making the announcement. "Science is ever evolving."
At an afternoon news conference in Washington, Mr. Johanns described
serious errors in the testing in the United States on the animal, the
second one found with mad cow disease, formally known as bovine
But he also defended the safety of American beef, reminding reporters
that the animal had been incinerated rather than being ground into
hamburger, as the first one was in late 2003.
"I enjoyed beef this noon for lunch," Mr. Johanns said. "It is the
safest beef in the world."
The head of the testing laboratory in Weybridge, England, who joined the
news conference by telephone, said he was "pretty confident" that the
incidence of mad cow disease in American herds was "very little indeed."
Of 388,000 tests in the last year, only three positive rapid tests have
been found, and only this one has been confirmed.
Until yesterday, the Agriculture Department used a rapid test called an
Elisa and confirmed any positives with a slower immunohistochemistry
test, which it calls the "gold standard."
The Europeans and the Japanese use those tests, but routinely add a
confirmatory Western blot test, which is more sensitive.
The Agriculture Department asked the English laboratory, regarded as one
of the world's best, to retest the samples.
In response to questions, Dr. John Clifford, the Agriculture
Department's chief veterinarian, revealed another surprise: the animal's
disease strain did not closely resemble the British-style strain found
in the first mad cow, which was born in Canada and raised in Washington
Instead, it was closer to a strain found in France - a result, another
scientist said, that suggested that the infection had come from a
different pool of infected feed, possibly imported from France.
Despite the Agriculture Department's assurances, critics said the
dispute revealed serious flaws in the testing regimen used here for 15
"All this foot-dragging has got to stop," Michael K. Hansen, a senior
research associate at Consumers Union, said excitedly.
"They waited seven months to do this test?" Dr. Hansen asked. "And they
didn't even bother to write up a report?"
Like other critics, Dr. Hansen called for testing all animals over 20
months old, and for bans on feeding poultry litter that has spilled
cattle meal in it back to cattle, giving calves "milk replacer" made
from cattle blood and letting cows eat dried restaurant "plate waste."
Dr. Hansen said the feed bans that the department refers to as its
"firewall" were "more of a white picket fence."
Mr. Johanns refused to give details about the animal, other than to
repeat that it was born before the 1997 ban on feeding ruminant protein
to ruminants, that it was raised for beef, not dairy, and that it was
too crippled to walk when it was killed.
There was "no evidence" that it was born outside the United States, Mr.
Johanns said, and its brain was sampled for tests at a plant
specializing in diseased and dead animals. Most beef animals are
slaughtered when they are less than 3 years old.
DNA tests will be started to find the herd it was raised with, Mr.
Johanns said. Normally, an infected animal's whole herd is slaughtered
on the assumption that all ate the same feed.
He described several errors in the testing process in the United States:
¶The brain samples were frozen, which makes some tests harder.
¶Parts from five carcasses were temporarily mixed up.
¶No written records were kept.
Also, after the animal tested positive on two rapid Elisa tests and then
negative on the slower, "gold standard" test, another "experimental"
test was done that came up positive.
Mr. Johanns would not describe it, but an Agriculture Department Web
site said it was an enhanced version of the "gold standard" test.
That was all the more reason further testing should have been done
without delay, Dr. Hansen said.
Mr. Johanns became agriculture secretary in January.
Two weeks ago, the department's inspector general, Phyllis K. Fong,
initiated a further test here - the Western blot - because of the
earlier confusion. Mr. Johanns complained yesterday that it was done
without his knowledge.
A lawyer for Ms. Fong's department refused to say yesterday whether she
had ordered it or had the authority to do so.
Representative Henry A. Waxman, Democrat of California and a ranking
member of the Government Reform Committee, who has criticized the
department's testing regimen, praised the inspector general yesterday
but said, "The Agriculture Department should have gotten it right in the
Mr. Waxman added, "The administration's response to mad cow disease
appears to be more public relations than public health.
"Today's announcement exposes the error in the administration's
Ed Loyd, an Agriculture Department spokesman, said yesterday's
announcement that all positive rapid tests would now be confirmed both
with the immunohistochemistry test and a Western blot "took care" of
such complaints and showed that the department was not complacent.
Mr. Johanns also ordered the Agriculture Department's national
laboratory in Ames, Iowa, to reassess the antibodies in its
immunohistochemistry test because the British laboratory's antibodies
attached to the misfolded brain proteins, called prions, that cause the
disease, while the American laboratory's apparently did not.
The test is not purchased off the shelf, he said, and every laboratory
must make its own.
Mr. Johanns said that the animal did not have many prions and that they
were concentrated in unusual areas of the brain, so one laboratory's
test might miss the infection while another caught it.
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