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Milk Supply Appears Safe from Mad-Cow Transmissibility

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Jan. 28--When a slaughtered Yakima County cow tested positive for mad-cow disease in December, government officials rushed to track down the meat and get it off the market, even though it was considered safe to eat.

They made no move, however, to halt the flow of milk to stores from the same dairy farm that had been home to the sick animal -- not even while they evaluated the herd's risk for mad-cow disease, or bovine spongiform encephalopathy (BSE).

Why the different policy for milk? And -- some consumers couldn't help but wonder -- does science back it up?

The U.S. Food and Drug Administration quickly issued a statement saying studies indicate milk cannot transmit BSE to humans.

Numerous other major health agencies agree, among them the World Health Organization and the watchdog, Parliament-created Food Standards Agency in Britain, where most of the world's mad-cow cases have occurred.

Sy, a neuroscientist at Case Western Reserve University in Cleveland, Ohio, thinks milk almost certainly would be safe even if it came from a cow with BSE.

Sy collaborates on research with Case Western's National Prion Disease Pathology Surveillance Center, which studies BSE and related diseases.

He said studies in Britain have failed to find evidence of BSE infectious material in milk from infected cows.

That material involves a malformed protein, or prion, which scientists say is the cause of BSE and its human form, variant Creutzfeldt-Jakob Disease.

Yet even though Sy is convinced milk from BSE-infected cows would be safe to drink, he says existing technology cannot offer absolute certainty. It's theoretically possible that current tests can't detect extremely small quantities of the prions, he said.

"Absence of proof is not proof of absence," Sy said.

Tiny, undetectable quantities of the prions, if they exist in milk, might or might not be sufficient to cause the disease in humans, Sy said, though he considers the risk highly unlikely.

Beef muscle meat -- steaks, roasts, etc. -- also is considered to be free of the culprit prions, which are believed to occur primarily in neurological tissue such as the brain and spinal cord. Officials said the sick Yakima County cow's meat was recalled only out of "an abundance of caution." U.S. Department of Agriculture (USDA) officials gave the same reason for slapping quarantines on dairy farms linked to the mad-cow case -- although they allowed milk production to continue.

Shortly after the BSE-infected cow was discovered, the International Brotherhood of Teamsters petitioned the federal government to also ban milk from the quarantined dairies. Members of Local 66 have been locked out by Seattle-area Darigold plants since Aug. 31 as a result of failed contract negotiations.

When the USDA ignored the petition, union members passed out leaflets at local grocery stores but stopped after the quarantines were lifted Monday, said Mark Jones, secretary-treasurer of the local.

Britain's Food Standards Agency points to a study in which mice failed to contract BSE even though fed large volumes of milk from BSE-infected cows.

And the agency notes that in another study no cases of BSE were detected in the offspring of BSE cows, despite suckling their mothers' milk for at least a month.

But even these studies, a few critics say, fail to present absolutely conclusive safety evidence. Some raise the possibility that a species barrier may inhibit BSE from infecting mice through milk. Others assert that some of the sick cows' offspring may have been too young to exhibit BSE symptoms.

Consumers weighing the odds of contracting the always-fatal human form of the disease through milk may have mainly this to go on: Most experts, including major health organizations, say there's no evidence that it's ever happened and next-to-no likelihood that it could.

Michael Hansen of Consumers Union has been sharply critical of government assertions about the safety of the U.S. beef supply, but even he agrees about milk.

Milk does contains white blood cells, which could carry the infectious agent, Hansen said. "There's a theoretical risk, but its down near the bottom of the hierarchy," he said. "I would be worried about a lot of other things before I would be worried about milk."

Sy said there's comfort in the fact that only about 150 human cases have been recorded worldwide, even though BSE has been detected in some 100,000 cows, mainly in Britain. The only person diagnosed with the disease in the United States is believed to have contracted it in Europe.

Sandi Doughton contributed to this story.


-- A federal agency is investigating whether commodities traders profited last month from advance knowledge of the first U.S. case of mad-cow disease. The Commodity Futures Trading Commission is looking into cattle futures trading data on the Chicago Mercantile Exchange as far back as Dec. 9 -- the day the diseased Canadian Holstein was slaughtered in Washington state and two weeks before the Department of Agriculture confirmed the animal had mad-cow.

-- The United States is working with other countries to avoid shutting down trade when a single cow is found with mad-cow disease, Agriculture Secretary Ann Veneman said yesterday. Countries across the globe halted U.S. beef imports after Veneman announced last month that a single cow had mad-cow disease. The United States has similarly banned imported beef from countries that discovered mad-cow. Also agreeing is Man-Sun Sy, one of this country's leading researchers on the brain-wasting disease -- though he says the possibility of BSE-infected milk cannot be absolutely ruled out with current technology.


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(c) 2004, The Seattle Times. Distributed by Knight Ridder/Tribune Business News.


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