BSE: Could it happen here? Experts say probably not

Published on February 15, 2001
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In his last press conference before leaving office, former Agriculture Secretary Dan Glickman identified bovine spongiform encephalopathy as one of the major issues that will be faced by incoming secretary Ann Veneman. Daily news stories about the development of the so-called "mad cow" disease in Europe have the American public fearful of what would happen if the disease were to strike here. McDonald's earnings have fallen and stock price has plunged because of decreased beef sales in Europe.

As BSE continues its spread in Europe, with several countries reporting their first cases in recent months, US authorities are fine-tuning defensive actions to prevent the arrival and spread of the disease.

European woes
Since the discovery of the disease, almost 200,000 cases of BSE have been identified in the United Kingdom. As of Jan 25, 2001, the disease have been detected in 12 other European countries, including 503 cases in Portugal, 499 in Ireland, 366 in Switzerland, and 218 in France, according to the Office International des Epizooties.

What to tell your clients*
1 We have not identified BSE in the United States. We're looking, and we continue to look very hard.
2 To the best of our knowledge based on all the research, the agent is found in the brain and spinal tissue. It has not been found in meat. But we are double- and triple-checking those results.
3 We have had no cases of new variant Creutzfeldt-Jakob disease in the United States to date.

For more information:
USDA-APHIS updated information on BSE and other TSE, including fact sheets and a frequently asked questions page
A resource provided by the National Cattlemen's Beef Association and reviewed by a panel of scientific experts, including Dr. Detwiler and Dr. Hueston
World Health Organization fact sheet on BSE
Updated information on BSE in the European Union
BSE information from the British Ministry of Agriculture, Fisheries, and Food

*Three recommendations provided by Dr. William D. Hueston

European countries are slaughtering so many cattle, they don't know what to do with them; Ireland alone plans to destroy 300,000 by summer, and through its "purchase for destruction" program the European Union expects to buy 2 million head of doomed cattle by the end of June.

No cases of BSE have been found in the United States despite 10 years of surveillance, according to Dr. Linda Detwiler, senior staff veterinarian for USDA-APHIS. No reported cases of new variant Creutzfeldt-Jakob disease, the human brain disease scientists believe may be linked to BSE, have been discovered here either. More than 90 people have died of nvCJD in Europe, most in the UK.

US animal and health regulators must be on guard, however, said BSE expert Dr. William D. Hueston, who recently completed a six-year term on the British Spongiform Encephalopathy Advisory Council. German health and agriculture ministers were forced to resign in December after BSE showed up in their cattle population despite their assurance that the country's food supply was safe. American officials shouldn't make the same mistake by saying the United States will never have the disease, Dr. Hueston said.

"But what we need to say is that we've taken a series of preventive measures, and because of the preventive measures we've taken, we think the likelihood is pretty small," he said. Dr. Hueston now consults for government agencies and industry, and serves as professor, chair of veterinary medicine, and associate dean at the Virginia-Maryland Regional College of Veterinary Medicine.

Protecting cattle and people
Since 1988, when the USDA established a BSE working group to suggest regulatory approaches, the USDA and the FDA have implemented measures to stop the spread of BSE if an infected cow were ever to reach our shores.

Between 1981 and 1989, the year the USDA banned the import of ruminants from BSE-infected countries, 496 cattle were brought to the United States from the United Kingdom and Ireland. The USDA has traced these cows and found all but 35, and the four known to be alive in America are quarantined and monitored by state veterinarians and APHIS. An additional 36 head of cattle imported from other European countries in 1996 has been quarantined as well. The agency continues to monitor these animals and try to purchase them. None of these imported animals has displayed signs of disease.

One of the most effective controls against the disease is APHIS's targeted surveillance program, Dr. Hueston said. Sensitive immunohistochemical tests and standard histopathologic tests are used to evaluate the brains of cattle that are most likely to have the disease, such as downer cattle and those with signs of neurologic disease either in the field or at the time of slaughter, as well as cattle brains submitted to veterinary or public health laboratories that test negative for rabies or other brain diseases.

The European Union now tests or destroys every cow over 30 months of age, and Germany has lowered its testing age to 24 months. The United States had tested 11,954 cattle brains as of Dec 31, 2000, a seemingly small number compared with Europe. But because the tests are targeted, they are more effective at determining whether we have BSE in this country, Dr. Hueston said.

"For every test we run, we have the highest chance of detecting BSE, if BSE exists, without giving the public a false sense of security" by testing cattle unlikely to have the disease, he said.

In 1997, the FDA issued a rule prohibiting the feeding of most mammal-derived products to ruminants, and the USDA banned imports of live ruminants and most ruminant products from all of Europe. Prior to the official ban, cattle producers had implemented a voluntary ban. On Dec 7, 2000, the USDA banned all European imports of rendered animal proteins, regardless of species.

Enforcing regulations
Although many such regulations aim to prevent the spread of the disease to or within the United States, compliance with the rulings issued by government agencies is another matter.

In late January, the FDA announced it had isolated a herd of cattle in Texas that were accidentally fed extremely small amounts bovine meat and bonemeal. Because feeding infected ruminants to cattle contributed to the spread of the disease in Europe, the FDA outlawed it in 1997. In this case, because the feed was made of products from American cows, there was little threat of actual disease, according to the Texas Animal Health Commission. But as a further precaution, the animals will not be sold for food.

Critics say this is symptomatic of a larger compliance issue, and this isn't the only documented case of non-compliance. On Jan 10, the FDA-CVM released survey findings that showed 16 percent of 180 renderers and 20 percent of 347 licensed feed mills were not properly labeling their rendered ruminant products. In addition, 28 percent of renderers did not have a system to prevent commingling of these products with their other feed products.

Compliance may be less than perfect, Dr. Hueston said, but there are so many precautions along the path that takes cattle from farm to plant to human that he likens BSE to winning the jackpot at a slot machine. A large number of mistakes or chance happenings would have to line up exactly right for BSE to spread.

"We've put in a number of hurdles, and while no one is 100 percent effective, the cumulative effect of the series is pretty darn good," he said.

George Gray, a researcher at the Harvard School of Public Health, also said that complacency and disobedience of the law could be a problem, but that overall, the likelihood of the disease spreading here is low.

Gray heads up a Harvard study commissioned by the USDA to assess the government's risk management efforts. The official results of the investigation won't be released until spring, but Gray said in an interview that his hunch is that "things are in pretty good shape."

"I came into this a beef eater, and I'm still a beef eater," he said.

The USDA and the FDA have been working together for years to help enforce regulations, Dr. Detwiler said. Because APHIS officials are out in the field helping farmers and ranchers, they are working to educate producers about the disease and the necessary precautions to avoid it.

Should we do more?
The US government continues to consider more preventive measures as more knowledge about the disease becomes available. "We always need to be closely scrutinizing the science," as government officials have for the past 10 years, to make sure we are doing enough, Dr. Detwiler said.

Potential actions include extending bans that already bar people who have lived in the UK for more than six months between 1980 and 1996 from donating blood. At a January meeting of the FDA's Transmissible Spongiform Encephalopathies Advisory Council, government advisers recommended that the FDA consider including people who had lived in France, Portugal, or Ireland for 10 years or more in the ban.

Concerns were also raised at the meeting about TSE in other animals. Scrapie in sheep and chronic wasting disease in elk and deer have been found in the United States, but for now, scientists do not think they pose a serious threat to humans.

A study of three Creutzfeldt-Jakob disease cases among victims who had eaten deer or elk meat did not reveal any link between that disease and chronic wasting disease, according to a presentation made at the meeting by Ermais Bely, MD, of the Centers for Disease Control and Prevention. The advisory panel considered recommending a ban on blood and tissue donations from hunters and others exposed to CWD, but decided the evidence did not warrant it.

In addition to government regulations, individual companies have started self-regulating to protect themselves from bad publicity, Dr. Hueston said. For example, at least one major feed manufacturer has removed ruminant meat and bonemeal from all of its feed formulations.

And although the United States has no formal ban on nervous tissue—where scientists believe the infectious agent is found—in beef products, "the likelihood that there is brain and spinal cord in your processed meat is far less than it was 10 years ago," he said. "The big companies are actively looking at ways to reduce risk."

Education is the key
Veterinarians must play a key role in the effort to prevent the spread of BSE and the spread of fear, Dr. Hueston said.

In addition to keeping informed about the disease and recommending cattle for testing, food animal veterinarians must educate their clients about the need to comply with the ruminant feed ban, Dr. Detwiler said. Small animal veterinarians have their part, too—they should be on the lookout for the rare but fatal feline spongiform encephalopathy, signaled by loss of motor function and drowsiness in cats.

More than increased regulations, Dr. Hueston said he thinks educating veterinarians and the public about the disease will be the most important future action.

"Every food animal veterinarian out there has a responsibility to help identify animals that should be tested," he said. "And small animal veterinarians need to learn enough about the disease so that they can responsibly answer their client's questions. They're going to ask their veterinarian about it, not their doctor."

Dr. Detwiler said she agrees that veterinarians must be a resource for the public. "The more of us that talk to the end users of the product, the better," she said.