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Mad Cow fears lead growing list of nations to halt beef imports
(Thursday, Dec. 25, 2003 -- CropChoice news) -- Shankar Vedantam, Washington Post:
Federal officials announced the recall yesterday of more than 10,000 pounds of meat that passed through a Washington state slaughterhouse on the same day as a Holstein cow infected with mad cow disease.
Fearing that contaminated beef could pose a threat to their food supply, Canada and Mexico joined several other countries in halting U.S. imports. The U.S. beef industry was battered as financial markets predicted steep drops in demand, with beef prices dropping sharply along with the stocks of meatpacking companies and restaurant chains such as McDonald's and Wendy's.
Federal investigators, meanwhile, frantically sought to track down the infected cow's antecedents. Agriculture officials said the Holstein was probably infected before it was purchased by a farm in southern Washington, which sent it to the slaughterhouse on Dec 9. Because the disease is transmitted through contaminated cattle feed, other cows from the birth herd may have eaten the same feed, widening the circle of risk to animals now widely dispersed or already in the food supply.
"Potentially other animals at the same age were fed the same feed," said David Ropeik, director of risk communication at the Harvard Center for Risk Analysis, which has studied the potential impact of mad cow disease in the United States. "There might be other animals carrying the infected material that aren't symptomatic yet."
Federal officials issued assurances of public safety while keeping a nervous eye on the health of the beef industry, the largest component of U.S. agriculture. The State Department has cabled all embassies and asked diplomats to tell foreign governments that the problem is under control, officials said.
U.S. officials insisted that the nation's beef is safe because of a safety regimen instituted in 1997, which protects cattle from infected feed. As part of the same regimen, the brain and spinal cord of the infected Holstein were removed at the slaughterhouse and sent to a rendering plant.
But food safety advocates who say the safety ban is inadequate point out the Holstein cow was infected after the safety ban took effect. Given that mad cow disease has about a three-year incubation period, the Holstein was probably infected around 1999 or 2000, they said.
In an interview yesterday, Tom Ellestad of Vern's Moses Lake Meats, the slaughterhouse where the Holstein was killed, said that he distinctly remembered the infected cow. Contradicting government officials, Ellestad said the cow was not a "downer" animal -- that it was able to stand and even walk.
Ellestad said his family has been operating the slaughterhouse since 1970, and the recall imposed on the 20 carcasses shipped from the facility on Dec. 9 was the first in its history. Government officials said the recall was being implemented to shore up public confidence in the food supply, not because of any known risks. Agriculture Secretary Ann M. Veneman said the recall was ordered out of "an abundance of caution."
Mad cow disease is the popular term for bovine spongiform encephalopathy, or BSE, a disease caused by a misshapen protein known as a prion. In humans, prions are associated with a fatal brain-wasting disorder called variant Creutzfeld-Jakob disease. Since the 1980s, when the first cases of mad cow disease were found, 154 people have died, mostly in Britain, and millions of cows have been slaughtered to keep the disease from spreading. The only known channel of infection is through animal feed -- in England the problem was compounded because the brains of infected animals were being ground up and fed to other cattle. The 1997 U.S. ban aims to halt this practice.
This Holstein is the first infected animal to be discovered in the United States. USDA officials who are handling the investigation said the Holstein came from a large dairy farm in southern Washington. The farm has two premises with more than 4,000 cows, Veneman said. The USDA declined to identify the facility, but an informed source said that the Holstein came from the Sunny Dene Ranch in Mabton.
Officials said farm records showed that the Holstein was purchased in October 2001 and that it was about two years old at the time -- making it about four years old when slaughtered, a revision of an earlier estimate. Because mad cow disease typically takes at least three years to incubate, investigators believe the cow became infected before it was acquired by Sunny Dene Ranch.
"In all likelihood, the animal consumed contaminated beef in a previous herd than the one it was culled from," said Stephen Sundlof, director of the Food and Drug Administration's Center for Veterinary Medicine. "We are trying to track down some of this information."
Farm records have narrowed the source of the animal's birth herd to two other farms. Neither was identified, but USDA officials said both were in Washington state. After finding the birth farm, investigators will still have to track down all the suppliers of feed to that farm -- and then determine how widely the supply of contaminated feed might have been distributed. At the farm where it was acquired, the Holstein cow suffered complications during its first calving, which resulted in its being partially paralyzed, USDA officials said.
"It's not uncommon practice for animals that are no longer economically profitable to send them to slaughter," said W. Ron DeHaven, deputy administrator and chief veterinary officer of the USDA. "Whether this animal had recovered ambulation before slaughter we don't honestly know."
The confusion may explain the discrepancy between the USDA's description of the Holstein as a downer cow and Ellestad's recollection that the animal was ambulatory. The issue of whether the animal was a downer is significant because of a growing controversy over whether such animals should be part of the food supply. Congress weighed the question recently and may revisit it soon; a ban is championed by many food safety advocates.
At the Moses Lake slaughterhouse, USDA inspectors examined the animal and approved it for slaughter. Kenneth Petersen, a USDA Food Safety and Inspection Service official, said that records indicated the animal had shown no signs of injury or disease other than inflammation and a hemorrhage in the pelvic canal that was consistent with the birthing injury. Ellestad said the facility did not use a technique known as advanced meat recovery, which some consumer groups say can pull infected tissue into meat that goes into the food supply.
Routine samples were taken from the Holstein for BSE analysis, and the results became available 13 days later.
Bryan Dierlam of the National Cattlemen's Beef Association said the group had recommended a "test and hold" strategy, in which killed downer animals would not be sent into the food supply until they were cleared by the tests. DeHaven said the USDA will consider the idea.
The decisions by several major importers of U.S. beef to halt imports is hardly surprising -- the United States imposed bans on Canadian beef imports after a single case of mad cow disease was discovered in Alberta in May. Some of those measures are still in place, but the government is planning to lift them, DeHaven said.
"What's going to happen in the marketplace is going to hinge on how this investigation turns out," said Keith Collins, the USDA's chief economist. U.S. beef imports have been halted by Mexico, Canada, Japan, South Korea, Hong Kong, Taiwan, Singapore, Malaysia, Russia and South Africa. Together, they account for most of the $3.4 billion U.S. export market.
Limited action on U.S. commodity markets yesterday showed the potential impact for the industry: The market opened with the price for live cattle having already fallen as much as it is allowed to fall in a single day. Trading will resume on Friday, and officials expect prices to fall again.
Ropeik from Harvard's Center for Risk Analysis said that the apparent breach that allowed the Holstein to become infected in 1999 or 2000 was troubling -- and could be a sign of more widespread problems. But a computer model analysis had shown, however, that even if there were 500 infected cows, the disease would not expand, because sooner or later infected tissue would get picked up by the feed ban and be diverted from both cattle feed and human consumption.
"Even with incomplete compliance with the ban, there is enough compliance so that it basically chokes itself off," he said.
Harder to measure with computer simulations is the perception of danger in the food supply. A host of groups have seized on the mad cow finding to advance a range of different agendas: On a rainy sidewalk outside the USDA headquarters in Washington yesterday, for example, the animal rights group, People for the Ethical Treatment of Animals, handed out brochures on how to go vegetarian.
Source: http://www.washingtonpost.com/wp-dyn/articles/A29003-2003Dec24.html
Mysterious Proteins to Blame
By Rick Weiss
Mad cow disease is one of a family of fatal diseases in humans and other mammals caused by bizarre infectious agents unlike any others known to biology.
Neither viruses nor bacteria nor single-celled protozoans, these infectious elements, known as prions (PREE-ons), consist of a mere strand of protein and carry no DNA or other genetic material -- a fact that for years left most scientists skeptical about the prions' ability to cause disease.
How, scientists wondered, could something multiply within an animal's body and even spread to other animals if it could not make copies of itself? And how could something make copies of itself without hereditary material such as DNA?
For answering those two questions, California scientist Stanley B. Prusiner won a Nobel Prize in 1997.
Prusiner found that prions ("proteinaceous infectious particles") are tiny pieces of protein, even smaller than viruses, that can exist in two forms -- a "normal" form and an infectious, disease-causing form. The two are virtually identical, except one is folded and tangled into a slightly different shape than the other.
Researchers are not sure what normal prions do, though there is some evidence they play a role in transporting copper within the body.
But Prusiner found that once an aberrantly shaped prion finds its way into an animal (by hitchhiking within contaminated meat products, for example), it can attach itself to a normal prion in the body and force that prion to adopt its "bad" conformation. So unlike standard infectious agents that make more of themselves through replication -- in effect, having babies -- "bad" prions make more of themselves by recruiting good prions to their cause. In the end, the effect is the same: An expanding wave of conversions results in more and more "bad" prions accumulating in the body. They travel through the animal's nervous system and begin to take a toll on the brain.
Over time they cause pockets of nerve damage, giving the brain a spongy appearance and inexorably killing the animal.
Prion diseases, known collectively as "transmissible spongiform encephalopathies," or TSEs, vary depending on the animal in which each occurs. In cows, there is mad cow disease. In sheep, it is called scrapie. In humans, prions cause Creutzfeld-Jakob disease, Gerstmann-Straussler-Scheinker syndrome, fatal familial insomnia and kuru (a disease that for decades affected a tribe in Papua New Guinea that had a tradition of eating the brains of dead relatives).
In the mid-1990s scientists recognized a new version of human prion disease, called variant Creutzfeld-Jakob disease, caused by eating beef from prion-infected cows. As in other prion diseases, the incubation period between infection and appearance of symptoms is long -- as long as four decades -- making it very difficult to track the source of infection and also difficult to stop an epidemic early, since it is invisible for many years.
There is no treatment for prion diseases, and prions are virtually indestructible. The proteins are resistant to standard means of sterilization, including heat, chemicals and radiation -- which is why the United States and other countries have since 1997 banned the use of even processed beef parts in feed for cattle.
There is no test for prion infection in live animals; all tests are done postmortem using central nervous tissue, where the proteins are present in highest concentrations.
"It's very tricky," said Giuseppe Legname, a prion disease researcher at the University of California at San Francisco. "You need something that can discriminate between the infectious and non-infectious forms."
Legname counts himself among those who would like to see a more thorough system of testing for mad cow disease in this country. He suggested that both safety and public confidence could be boosted if this country switched to the Japanese system of using a less-than-perfect but rapid test for mad cow to check every cow for prion infection before releasing the animals' meat into the food supply. The more precise tests used today by the Agriculture Department require that tissues be "pickled" and treated in a complex set of steps that take several days before results emerge -- by which time the meat may be well beyond recall.
In November, the congressionally chartered Institute of Medicine released a report on prion science recommending that the federal government fund a significant amount of new research aimed at understanding the basics of prion diseases, in part so more rapid and accurate tests can be developed.
http://www.washingtonpost.com/wp-dyn/articles/A28919-2003Dec24.html | |
