February 24, 2005
Hon. Mike Johanns
Secretary of Agriculture
US Department of Agriculture
1400 Independence Avenue, SW
Washington, DC 20250
Dear Secretary Johanns:
We appreciate having had the opportunity to meet with you on February 9, 2005 with the Food Safety Coalition. Because we had limited time on that occasion, we are following up with a letter explaining our concerns on one issue that is especially important to Consumers Union: USDA’s bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, testing procedures.
For reasons we explain below, we urge USDA to expand its testing protocol to bring it in line with those of Europe and Japan, by including a test called the “Western blot” when evaluating cows suspected of mad cow disease, such as the suspect cow identified in November, 2004. Under current USDA testing protocols, it is possible that USDA will miss cases of mad cow disease that could be confirmed through additional testing.
As Secretary of Agriculture, you face the important and very difficult responsibility of preventing mad cow disease in the United States. Given the potential consequences to both public health and the cattle industry if this brain-wasting disease were to become established here, it is extremely important that every scientifically justifiable step be taken to prevent it. It is especially critical to understand to what extent the disease may already be present in the United States, now that one case was discovered in Washington State in December, 2003.
As you know, the USDA has tested some 230,000 cattle since June, 2004, for mad cow disease. Although this seems like a large number, it is still less than 1% of the 35 million cattle slaughtered annually in the US. The number of cows tested should be increased.
Consumers Union also believes that USDA’s testing protocol should be expanded. USDA’s testing protocol specifically does not include the Western blot test (accompanied by a sodium phosphotungstinic acid [NaPTA] precipitation step), a test used by all European Union countries and Japan. When a cow in the USDA testing program is considered suspect as a result of positives in two runs of the Biorad quick test, as happened in November, 2004, it is sent to the USDA Ames Iowa laboratory for further evaluation. That evaluation includes only an immunohistochemistry test (IHC), which USDA refers to as the “gold standard.” We disagree with that characterization. Recent studies in Belgium1 and Japan2 have shown that the IHC test misses some cases of mad cow disease. A letter in last month’s Veterinary Pathology, from one of the world’s leading authorities on mad cow disease testing, pointed out that the Western blot, when accompanied by the NaPTA step, is far more sensitive than IHC in detecting the mad cow disease infectious agent3.
In fact, USDA used both the IHC and Western blot tests to confirm its first case of mad cow disease, in December 2003. According to a USDA publication, the Western blot test was “crucial” to identifying that case. It is thus difficult to understand why USDA did not again use the Western blot test along with IHC on its second suspect cow.
We therefore urge you to go back and retest–using the Western blot test with the NaPTA step–the suspect cow that was identified in November, 2004, and to send appropriate material from that cow to the United Kingdom laboratories for an independent evaluation. We further urge you to revise USDA policy and routinely use the Western blot test with the NAPTA step, as well as the immunohistochemistry (IHC)
test, for confirmation of suspect mad cow cases.
The USDA should operate out of an “abundance of caution” in its efforts to keep the US food supply safe from BSE. The experience of the United Kingdom, where millions of cattle had to be destroyed, beef exports were blocked for many years, and 147 people have died, painfully demonstrates the consequences of insufficient action to prevent the spread of mad cow disease.
The trust of American consumers, and of foreign markets, in the safety of American beef, rests on having confidence that USDA is utilizing the best science available, comparable to that used in other scientifically advanced countries.
A copy of a prior letter on this subject, which we sent to Dr. John R. Clifford, Deputy Administrator of the Animal Plant Health Inspection Service, is attached and we understand is in the process of being answered.
We look forward to hearing from you about whether you will direct USDA to retest the November 2004 suspect cow and revise USDA policy to routinely use the Western blot as well as IHC on all suspect animals.
Jean Halloran, Director, Consumer Policy Institute
Michael K. Hansen, Ph.D., Senior Research Associate
Cc: Dr. John R. Clifford
1 De Bosschere, H., Roels, S. and E. Vanopdenbosch. 2004. Atypical case of bovine spongiform encephalopathy in an East-Flemish Cow in Belgium. The International Journal of Applied Research, 2(4).
Accessed at http://www.jarvm.com/articles/Vol2Iss1/DEBOSSCHERE.htm
2 Yamakawa, Y. et al. for the Expert Committee for BSE Diagnosis, Ministry of Health, Labour and Welfare of Japan. 2003. Atypical proteinase K-resistant prion protein(PrPres) observed in an apparently healthy 23-month old Holstein steer. Japan Journal of Infectious Disease 56:221-222. Accessed at http://www.nih.go.jp/JJID/56/221.pdf
3 Sigurdson, C., Glatzel, M. and A. Aguzzi. 2005. letter to the Editor. Veterinary Pathology, 42: 107.