USDA Orders Testing
Changes After US
Mad Cow Case

Patricia Doyle, PhD
From ProMed Mail
USDA Testing Changes Ordered After US Mad Cow Case
By Donald G. McNeil, Jr.
NY Times
Substantial changes in the nation's mad cow testing system were ordered yesterday after British tests on a cow slaughtered in November 2004 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 2nd one found with mad cow disease, formally known as bovine spongiform encephalopathy. 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 1st one was in late 2003.
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 3 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 [ELISA, enzyme-linked immunosorbent assay] 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 1st mad cow, which was born in Canada and raised in Washington State. 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.
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: (1) The brain samples were frozen, which makes some tests harder. (2) Parts from 5 carcasses were temporarily mixed up. (3) No written records were kept.
Also, after the animal tested positive on 2 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. 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.
The non-contributory remarks and comments have been deleted. Last week I asked a senior colleague in Austin, Texas whether he could confirm that this was a Texas cow, to which he replied, "No comment," so we can, I believe, safely assume that it was. Where it was raised as a calf is another question awaiting answers. - Mod.MHJ
Bovine Spongiform Encephalopathy In The US
Information received on 27 Jun 2005 from Dr Peter Fernandez, Associate Administrator, Animal and Plant Health Inspection Service (APHIS), United States Department of Agriculture (USDA), Washington, DC:
Report date: 27 Jun 2005.
A non-ambulatory or "downer" cow tested "inconclusive" for bovine spongiform encephalopathy (BSE) when tested by a rapid screening test in November 2004 but was confirmed positive in June 2005 using western blot test and an immunohistochemical test carried out at the OIE Reference Laboratory for BSE in Weybridge, United Kingdom.
As a downer, the cow was prohibited from entering the human food supply. The carcass of the animal was incinerated.
Source of outbreak or origin of infection: unknown or inconclusive. The affected cow was born before the United States instituted a ruminant-to-ruminant feed ban in August 1997. The USDA has initiated an investigation to determine the animal's herd of origin.
Canada Exceeds BSE Testing Target for 2005
Canada has surpassed its testing target established for 2005 for bovine spongiform encephalopathy (BSE) surveillance. The target for this year was 30 000 cattle and, as of 17 Jun 2005, there have been 32 363 samples collected and tested through the provincial and federal laboratory network in Canada.
The level and design of BSE testing in Canada is in full accordance with the guidelines recommended by the World Organisation for Animal Health (OIE). The samples collected target the highest-risk cattle within the national herd. This includes all animals over 30 months of age that are dead, down, dying or diseased, and clinical suspects of any age. This targeted surveillance program is crucial to defining the level of BSE in Canada and to confirming the effectiveness of the suite of measures in place to protect human and animal health from the disease. Based on the intensity and sensitivity of the testing program and the information collected in Canada's BSE investigations, the evidence continues to demonstrate that the prevalence of BSE in Canada is extremely low and continuing to decline.
"Surpassing this surveillance target at the mid-year point illustrates the effectiveness of the national BSE surveillance program and the high level of commitment from Canadian producers to finding the disease," said Minister of Agriculture and Agri-Food Andy Mitchell.
In 2004, a BSE Surveillance Reimbursement Program was implemented that provides payments to producers for their services when eligible samples are submitted to the national program. These payments assist producers in covering a portion of the veterinary examination fees and carcass disposal costs. Many provinces have also demonstrated their commitment by providing additional support to the reimbursement program through increased laboratory capacity, education and awareness campaigns, sampling assistance and financial supplements to the federal payments. This collective effort is critical to a successful national surveillance program and to the continued demonstration of vigilance in animal and public health and food safety in Canada.
Patricia A. Doyle, PhD
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