17 June 2009

Mad fish disease could threaten humans

by Kate Melville

Writing in the Journal of Alzheimer's Disease, neurologist Robert P. Friedland questions the safety of eating farmed fish that are fed byproducts rendered from cows, adding a new worry to concerns about the nation's food supply.

Friedland, from the University of Louisville, and his co-researchers suggest that farmed fish could transmit Creutzfeldt Jakob disease - known as mad cow disease - if they are fed bovine byproducts. The scientists urge government regulators to ban feeding cow meat or bone meal to fish until the safety of this common practice can be ascertained.

Creutzfeldt Jakob disease is an untreatable, universally-fatal disease that can be contracted by eating parts of an animal infected with bovine spongiform encephalopathy (BSE or mad cow disease). An outbreak in England attributed to infected beef prompted most countries to outlaw feeding rendered cow material to other cattle because the disease is so easily spread within the same species.

The probability of transmission of BSE to humans who eat farmed fish would appear to be low because of perceived barriers between species. But, according to Friedland, it is possible for a disease to be spread by eating a carrier that is not infected itself. It's also possible that eating diseased cow parts could cause fish to experience a pathological change that allows the infection to be passed between the two species.

"The fact that no cases of Creutzfeldt Jakob disease have been linked to eating farmed fish does not assure that feeding rendered cow parts to fish is safe. The incubation period of these diseases may last for decades," Friedland said. "We have not proven that it's possible for fish to transmit the disease to humans. Still, we believe that out of reasonable caution for public health, the practice of feeding rendered cows to fish should be prohibited."

"Fish do very well in the seas without eating cows," he added.

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Source: Journal of Alzheimer's Disease