NEW YORK (Reuters Health) - Three U.S. scientists are concern about the potential of people contracting Creutzfeldt Jakob disease -- the human form of “mad cow disease” -- from eating farmed fish who are fed byproducts rendered from cows.

Mad cow disease, also called bovine spongiform encephalopathy is a fatal brain disease in cattle, which scientists believe can cause Creutzfeldt Jakob disease in humans who eat infected cow parts.

In the latest issue of the Journal of Alzheimer’s Disease, Dr. Robert P. Friedland, a neurologist at University of Louisville in Kentucky and colleagues suggest that farmed fish fed contaminated cow parts could transmit Creutzfeldt Jakob disease.

The scientists want government regulators to ban feeding cow meat or bone meal to fish until the safety of this common practice can be confirmed.

Eating fish at least two times a week is widely recommended because of the beneficial effects of omega-3 polyunsaturated fatty acids on the heart and brain, they note.

“We are concerned,” Friedland and colleagues write, that eating farmed fish may provide a means of transmission of infectious proteins from cows to humans, causing variant Creutzfeldt Jakob disease.

“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,” Friedland said in a prepared statement. “Fish do very well in the seas without eating cows,” he added.

The risk of transmission of made cow disease to humans who eat farmed fish “would appear to be low,” the scientists emphasize, because of perceived barriers between the species, but that’s no guarantee that it can’t happen.

“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,” Friedland said.

“The incubation period of these diseases may last for decades, which makes the association between feeding practices and infection difficult,” he points out.

“Enhanced safeguards need to be put in place to protect the public,” Friedland concludes.

SOURCE: Journal of Alzheimer’s Disease, June 2009.