The United States has banned shipments of cattle and livestock products from its largest trading partner, Canada, after the discovery of a case of mad cow disease there.
A single cow in Canada has been confirmed as having bovine spongiform encephalopathy (BSE), which is better known as mad cow disease.
The incurable brain-wasting illness led farmers in Britain to destroy millions of cattle in the 1980s and 1990s. A rare human form of the disease is thought to result from eating contaminated cattle products.
Lester Crawford, deputy commissioner of the U.S. Food and Drug Administration, says the U.S. ban covers more than just Canadian livestock and cattle.
"The biggest concern we have is with animal feed that might be exported from Canada to the United States, and so we are blocking any shipment of it to the United States," he said. "And there are also some other materials that contain protein from animals we're concerned about, but primarily we are concerned about feed."
He says the first BSE case turned up in Canada ten years ago, but did little damage to trade between the two countries.
"The 1993 event had very little effect because it was contained and Canada did a great job," he explained. "We believe this will be the same thing, but we don't know at this point."
The infected animal was an eight-year-old cow in the Canadian province of Alberta. Debbie Barr, a senior veterinarian with the Canadian Food Inspection Agency, says the cow did not show outward signs of the disease, but that the illness was confirmed as part of routine BSE surveillance.
"The only thing that we know right now is that we have one case in one cow," she said. "Certainly, our investigation, a key part of our investigation will be to determine where this cow has been in the eight years of its life."
Dr. Barr says Canada exports what she describes as a "huge amount" of cattle material to the United States, including a $1.6 billion export industry in Alberta, alone.
Meantime, Canadian officials say none of the infected cow's meat entered the food chain and its remains were sent for rendering.