Second Possible U.S. "Mad Cow" Found, Further Tests Pending; Didn't Enter Human Food Or Livestock Feed Supply, Feds Say; Updated w/ News Conf. Excerpts
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(June 11, 2005, updated w/ news. conf. excerpts) -- In a hastily called Friday night (June 10) news conference (extended excerpts below), the U.S. Dept. of Food and Agriculture (USDA) said a second cow in the U.S. has tested positive for "mad cow" disease on an internationally recognized confirmatory test but is undergoing further tests because it first tested "inconclusive" on a "rapid test"...and says the animal posed no danger to the public because it never entered the human food or livestock feed supply.
In a written release (posted verbatim below), USDA says the cow -- headed for slaughter at a facility handling animals unsuitable for human consumption -- was selected for testing because it was a "downer" that couldn't walk when delivered. An initial "rapid" test was inconclusive...but USDA's Office of the Inspector General (OIG) (which has been reviewing USDA's "mad cow" related activities) advised testing the cow (and two others) using a second test described by USDA as "an internationally recognized confirmatory test, the OIE-recognized SAF immunoblot test ("Western blot test)." It came back reactive (positive).
"Because of the conflicting results on the IHC and Western blot tests, a sample from this animal will be sent to the OIE-recognized reference laboratory for BSE in Weybridge, England. USDA will also be conducting further testing, which will take several days to complete."
The confirmatory tests on the other two animals were negative. USDA declined to say from where the animal which tested positive came. It said the carcass of the animal that tested positive never entered the human food or livestock feed supply.
In its written release, the agency said:
"Regardless of the outcome, it is critical to note that USDA has in place a sound system of interlocking safeguards to protect human and animal health from BSE-including, most significantly, a ban on specified risk materials from the human food supply. In the case of this animal, it was a non-ambulatory (downer) animal and as such was banned from the food supply. It was processed at a facility that handles only animals unsuitable for human consumption, and the carcass was incinerated."
During the news conference, U.S. Agriculture Secretary Mike Johanns and Dr. John Clifford, Chief Veterinary Officer, Animal Plant Health Inspection Service fielded questions, which included this exchange (USDA transcript):
REPORTER: "Yes, good evening. This is Peter Shinn from the National Association of Farm Broadcasters.
"Mr. Secretary, I don't mean to ask a difficult question, but it just immediately comes to mind. What exactly happened in terms of how could you have gotten it not right the first time? And what's the difference between the IHC and the Western Blot? That might be a question for Dr. Clifford."
SEC. JOHANNS: "Yeah. I'll ask Dr. Clifford to get in. It's not really a question of not getting it right. They are, both tests are accepted by the OIE. Both tests if you use those, they are accepted under the standard. So it's not a question of getting it right. All of the protocols were followed. We had the positive and the rapid response test, the IHC test was applied according to the protocols, and that is the test that has been used in the United States.
"And so it's not a situation where you've got one test that isn't accepted and one that is. They both are accepted. There are differences in the tests, and I'll let Dr. Clifford explain that.
"And maybe, Dr. Clifford, you can even explain if you would just what this test showed and how you went about getting through the testing process."
DR. CLIFFORD: "Thank you, Mr. Secretary. And yes, we're confident in the results of actually both of these tests. The IHC was negative for this sample. Actually the Western Blot test, if you go back to the December cow that was found from Canada the Western Blot that was run on that particular sample we used one milligram of tissue to run that test and was found to be a very strong positive.
"In order to find a positive in this particular case with this Western Blot, they had to enhance or enrich it, in which that basically means you're concentrating the abnormal protein. So they had to use 20 times the amount. You would have to use about 20 times the amount of tissue for this to determine to be a positive or reactive on the Western Blot versus the one that was discovered in December in the state of Washington.
"In addition, there are definite differences between these two tests. The IHC is internationally recognized, and why we chose that for our enhanced surveillance program is because that particular test does two things. It allows you to visualize the anatomic location where the lesions are most likely to be found which is the obex. At the same time it uses a staining technique on the prions, on abnormal prions in the tissue in that location.
"So that's what the IHC does.
"In the Western Blot case, it's actually a homogenate (sp) of a sample of brain tissue that is centrifuged and they concentrate the prion protein and then they use a protease to destroy the normal protein, leaving the abnormal protein present. And then basically that is run through a gel-type separation using specific antibodies that will give you bands.
"And they look at those bands and the molecular weight of those bands to determine the outcome of that test.
"So this test would actually be referred to as a weak positive test in this case for the Western Blot, and as a result of that and the unusualness of this case it's going to require additional testing before we can confirm one way or another whether this is truly BSE or not."
SEC. JOHANNS: "Doctor, somebody's going to ask you this so let me just ask it. When you say "weak positive," it would be helpful if you could describe what you mean by that."
DR. CLIFFORD: "What we mean by "weak positive," Mr. Secretary, is going back to the original case. It required and enrichment of these and a greater amount of normal tissue in order to enhance this outcome. So in order to find the abnormal protein present you had to use more material and concentrate it."
SEC. JOHANNS: "Okay, thank you. That's very helpful. We'll take the next question."
OPERATOR: "The next question will come from Joe Pelka (sp). Your line is open.
REPORTER: "Hi. Good evening, gentlemen. I actually have three questions. I think I can state them succinctly. First of all, why did the IG ask for a retest in this case? What do you expect they'll do differently at Weybridge that they do from Ames, Iowa, in the IHC testing? And which cow of the three or which animal of the three that had the earlier positives are we looking at tonight?
SEC. JOHANNS: "I'll answer the first one just as best as I can, and then Doctor, I'll just queue you up that I'll ask you to answer the final two.
"The IG has been looking at the surveillance. As you know, we've tested now 375,000 animals, and Secretary Veneman wanted to be sure that we were touching the right places-- regions of the country and etcetera to make sure that when that surveillance was done we were satisfied that we got a good surveillance of the herd.
"Again, keep in mind that was a surveillance effort; it was never portrayed to be a food safety approach.
"In that effort I believe that the IG decided just to make sure that all the bases were touched that this additional testing should be done. So go ahead, Doctor."
DR. CLIFFORD: "Thank you, Mr. Secretary. The reason we're sending this to Weybridge is because we feel this is an unusual case, and we'd like to have the assistance of an internationally recognized laboratory for BSE.
"The inconclusive that we're referring to here is the one that we gave notification of in November of 2004. I think it was actually November 15, 2004. With regards to the OIG's recommendation, I think that recommendation was based upon a strong reaction on the biorad test and the negative IHC, and in order for us to try to resolve those discrepancies that have been raised relative to that."
In December 2003, a dairy cow with bovine spongiform encephalopathy (BSE) -- a brain wasting disease with a 100% fatal human variant -- was discovered in Washington state dairy cow. For a time it halted billions of dollars worth of U.S. beef exports and raised questions about the safety of the U.S. food supply.
The agency said in its June 10 release, "We are committed to ensuring that we have the right protocols in place -- ones that are solidly grounded in science and consistently followed. After we receive additional test results on this animal, we will determine what further steps need to be taken and what changes, if any, are warranted in our surveillance program."
USDA release text follows:
STATEMENT BY DR. JOHN CLIFFORD REGARDING FURTHER ANALYSIS OF BSE INCONCLUSIVE TEST RESULTS
Since the USDA enhanced surveillance program for BSE began in June 2004, more than 375,000 animals from the targeted cattle population have been tested for BSE using a rapid test. Three of these animals tested inconclusive and were subsequently subjected to immunohistochemistry, or IHC, testing. The IHC is an internationally recognized confirmatory test for BSE. All three inconclusive samples tested negative using IHC.
Earlier this week, USDA's Office of the Inspector General (OIG), which has been partnering with the Animal and Plant Health Inspection Service, the Food Safety and Inspection Service, and the Agricultural Research Service by impartially reviewing BSE-related activities and making recommendations for improvement, recommended that all three of these samples be subjected to a second internationally recognized confirmatory test, the OIE-recognized SAF immunoblot test, often referred to as the Western blot test. We received final results a short time ago. Of the three samples, two were negative, but the third came back reactive.
Because of the conflicting results on the IHC and Western blot tests, a sample from this animal will be sent to the OIE-recognized reference laboratory for BSE in Weybridge, England. USDA will also be conducting further testing, which will take several days to complete.
Regardless of the outcome, it is critical to note that USDA has in place a sound system of interlocking safeguards to protect human and animal health from BSE-including, most significantly, a ban on specified risk materials from the human food supply. In the case of this animal, it was a non-ambulatory (downer) animal and as such was banned from the food supply. It was processed at a facility that handles only animals unsuitable for human consumption, and the carcass was incinerated.
USDA's enhanced surveillance program is designed to provide information about the level of prevalence of BSE in the United States. Since the inception of this program, we have fully anticipated the possibility that additional cases of BSE would be found. And, in fact, we are extremely gratified that to date, more than 375,000 animals have been tested for the disease and, with the exception of the conflicting results we have received on this one animal, all have ultimately proven to be negative for the disease.
USDA is committed to ensuring that our BSE program is the best that it can be, keeping pace with science and international guidelines, and to considering recommendations made by OIG and others in this regard. We are committed to ensuring that we have the right protocols in place-ones that are solidly grounded in science and consistently followed. After we receive additional test results on this animal, we will determine what further steps need to be taken and what changes, if any, are warranted in our surveillance program."
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