What consumers want to know about “Mad Cow Disease”
By Mike Payne
On April 24th, 2012 the US Department of Agriculture announced that routine surveillance testing had detected a California dairy cow with Bovine Spongiform Encephalopathy (BSE).
But why would the USDA’s announcement indicate that the detection of this cow represents no danger to the human food supply?
Some background is helpful in understanding not only this case, but BSE in general:
What is BSE?
Bovine Spongiform Encephalopathy (BSE) is a degenerative neurological disease of cattle caused by mis-folded proteins (“prions”) that accumulate in the central nervous system. Over a period of years these protein accumulations crowd and kill bovine nerve cells, causing abnormal behavior and leading to the disease’s common name of “Mad Cow Disease”. Historically BSE has been spread in livestock by the feeding of cattle-derived proteins back to cattle, a practice which has been banned in the United States since 1997. Contaminated feed was the cause of the BSE epidemic in the United Kingdom in the 1980s and 1990s, resulting in an decade-long outbreak involving some 180,000 cattle. Subsequently it was determined that, on rare occasions, people consuming tissues of BSE-affected cows could develop a neurological disease similar to both BSE and the human malady Creutzfeldt–Jakob Disease (CJD). Ultimately some 200 human cases of this “new-variant CJD” were identified in people living in the United Kingdom and Europe.
Is the U.S. Food Supply Safe?
Yes. The carcass of the animal detected this week was never presented for slaughter for human consumption and never entered the human food chain. More important than the detection and removal of this particular cow however, are the multi-layered regulatory precautions in place since the 1990s, precautions which are described below. Collectively these safety measures have been successful in protecting both U.S. consumers and livestock from outbreaks of BSE. To date, there have been no cases of BSE transmission to American consumers associated with beef produced in the United States. Lastly, a substantial body of scientific research indicates that BSE is not transmitted through milk.
Is this part of an “Outbreak”?
No. The current evidence suggests that the recently detected animal was a single, isolated case rather than part of an outbreak. Confirmatory testing demonstrated that the suspect animal was positive for “atypical” BSE, a spontaneous form that appears to occur rarely in individual animals. This sporadic form has been detected only twice before in US cattle, once in Texas in 2005 and again in Alabama in 2006. Sophisticated laboratory procedures (immunohistochemistry and Western Blot protein analysis) can differentiate between the spontaneous “atypical” form of BSE and the “typical” form associated with consumption of contaminated cattle feed. While the current case appears to be isolated, out of an abundance of caution State and Federal investigators are performing an extensive epidemiologic investigation which will include inspection of relevant animals, feed sources and records.
Are BSE Safeguards in U.S. Working?
Yes. Since 1997 the U.S. has implemented interlocking safeguards to protect human and animal health against BSE. Centered on prohibition of feeding ruminant-derived material back to ruminants, these precautions have to date prevented livestock outbreaks in the United States such as occurred in the United Kingdom in the 1980s and 1990s. Worldwide, similar preventative measures have ultimately reduced the number of BSE cases detected in foreign cattle from 37,311 in 1992 to just 29 in 2011. In order to ensure that U.S. safeguards are in place and effective, regulatory agencies continue an extensive BSE surveillance program. Since the surveillance program’s inception in 1990, more than 1 million cattle at greatest risk for BSE have been tested, with about 40,000 high-risk cattle tested annually. This program represents an aggressive surveillance, in fact exceeding international guidelines by 10 fold. Most importantly relative to human health, cattle tissues known to contain concentrations of the prion protein (such as brain, spinal cord, some small intestine, called Specified Risk Materials) are diverted away from the human food chain at slaughter. Lastly, non-ambulatory cattle (sometimes called "downer cows") are also prevented from entering the human food chain.
Taken as a whole, these three interlocking safeguards (the ruminant-to-ruminant fed ban, surveillance testing, removal of Specified Risk Materials from all cattle at slaughter), have been remarkably effective in preventing BSE in cattle from being transmitted to humans. There have been only three cases of “new-variant CJD” described in the United States. All three cases involved foreign nationals, two from the United Kingdom and one from Saudi Arabia. According to the U.S. Centers for Disease Control (CDC), there is strong evidence indicating that all three of these patients contracted disease while in their home country rather than during their stay in the U.S.
What is the University of California Doing to Help?
The University of California assists farmers in complying with the important feed regulations that prevent BSE from entering a herd.
Outreach materials from the University of California:
Additional information:
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