Dec 24, 2003 (CIDRAP News) Federal officials took pains to assure the public today that the risk of contamination in the US beef supply is very low following yesterday's announcement that the nation's first apparent case of bovine spongiform encephalopathy (BSE), or mad cow disease, had turned up in Washington state.
"We continue to believe that the risk to human health in this situation is very low," Agriculture Secretary Ann M. Veneman said at a news briefing today.
A "presumptive case" of BSE was identified in a Holstein cow from a farm at Mabton, Wash., 40 miles southeast of Yakima, the US Department of Agriculture (USDA) announced yesterday. The disclosure sent shock waves through the beef industry and triggered numerous US trading partners to close their ports to American beef.
The case was found through routine BSE surveillance. Because the cow was a "downer"unable to walkat the time of slaughter on Dec 9, samples from the carcass were sent to a USDA veterinary laboratory in Ames, Iowa, for analysis. There, microscopic examination and immunohistochemical analysis of brain tissue pointed to BSE on Dec 22 and 23.
Samples were sent to an international reference veterinary laboratory in Weybridge, United Kingdom, for confirmatory testing. Veneman said the samples would arrive today and it would take 3 to 5 days to get the results. Other USDA officials voiced confidence that the findings would be confirmed.
Eating meat products from BSE-infected cattle is believed to be the cause of variant Creutzfeldt-Jakob disease. The United Kingdom has had 143 cases of the invariably fatal neurologic disease since BSE spread through British cattle herds in the 1980s and 1990s because of contaminated feed.
The firm that slaughtered the infected cow, Vern's Moses Lake Meats, Moses Lake, Wash., is recalling all 10,410 pounds of meat from cattle that were slaughtered Dec 9, the USDA announced late yesterday. The meat was very unlikely to be infected and was being recalled "out of an abundance of caution," the USDA's Food Safety and Inspection Service (FSIS) said.
The tissues most likely to contain the abnormal prion proteins believed to cause BSEthe brain, spinal cord, and distal ileumwere removed from the carcass and sent to rendering plants, USDA officials said. "Any of the tissues at risk that were harboring the infectious agent would've gone to rendering and not entered the human food supply," USDA veterinarian Ron DeHaven said at today's briefing.
Muscle meat from the infected cow was shipped to Midway Meats in Centralia, Wash., for deboning, Undersecretary for Food Safety Elsa Murano said at a briefing yesterday. From there the meat apparently went to two other Washington businesses, Willamette and Interstate Meats, for further processing, Murano said.
BSE does not spread directly from animal to animal; cattle apparently get the disease when they eat feed containing meat-and-bone meal from other infected animals. Since 1997, the United States and Canada have banned the use of meat-and-bone meal from ruminant (cud-chewing) animals in feed for ruminants. However, material form ruminants can legally be fed to nonruminants such as chickens. Chicken can be used in feed for ruminants, but BSE is not believed to be transmitted by that route.
The farm the infected cow came from, a large dairy operation with about 4,000 cows at two different sites, has been quarantined, USDA officials said. DeHaven said the fate of the cattle there has not been decided. He noted there is no evidence that infected cows transmit BSE to their calves, but the offspring of infected cows are usually tested as a precaution. Conclusive testing can only be done postmortem.
Besides tracing the fate of meat form the infected cow, the USDA said it was investigating the cow's history to learn how it became infected. DeHaven said the cow was culled from its herd Dec 9 because of paralysis that apparently resulted from complications of calving. The cow was bought and added to the herd in October 2001, when it was about 2 years old, he said. If the cow was 4 years old when it died, it was born about 2 years after the 1997 ban on putting ruminant protein into cattle feed took effect.
"Our investigation would focus on feeding practices at the birth herd where the animal was born," DeHaven said. He predicted that investigators may be able to identify the birth herd within "a day or two." Another USDA official said that BSE has an incubation period of about 4 to 5 years, so the cow likely was exposed to the disease in a herd other than the one it was culled from.
When the feed ban was first imposed in 1997, feed plants' compliance with it was about 75%, said Stephen Sundlof of the Food and Drug Administration's Center for Veterinary Medicine. "Since then we've achieved a level of 99% compliance, so it's improved dramatically during that time," he said.
In response to questions today about the use of "downer" cattle for food, Kenneth Petersen of the FSIS said a USDA veterinarian inspected the infected cow at the slaughter plant and found it acceptable. The cow had some inflammation and hemorrhage consistent with a birthing injury, findings that did not suggest the animal was unfit for use as food, Petersen said.
He added that samples from the carcass were taken as part of routine BSE surveillance, and at that point there was no particular reason to think that the carcass should be held until the test results were in.
The BSE case has already prompted a number of countries to suspend imports of US beef, USDA economist Keith Collins reported at today's briefing. They include Japan, South Korea, and Hong Kongthree of the biggest buyersas well as Taiwan, Singapore, Malaysia, Russia, and South Africa, he said. Two other major importersMexico and Canadahad not yet acted, Collins said.
The United States exports about 10% of its beef production, worth about $2.6 billion annually, according to Collins. "The suspension of sales by those major trading partners, which at this point would account for roughly 60 to 70 percent of our exports, is going to have a market effect," he said. "Where the market will settle out, it's too early to say.
Transcript of Dec 24 USDA news briefing
Transcript of Dec 23 USDA briefing