Safety system missed sick cow

A Washington Holstein cow probably was infected with mad cow disease a few months before safety bans on feed were enacted in 1997 in the United States and Canada, officials said Monday.

The infection probably occurred around the same time as a beef cow from Alberta, Canada, became sick. It was diagnosed with mad cow disease in May.

Scientists may need to increase monitoring of thousands of cattle born before the bans on potentially infected feed, which is how the disease spreads, officials said.

Repeating their insistence that the U.S. food supply is safe, agriculture officials also said they are searching for 81 Canadian-born cows from the same herd as the sick Holstein, which records indicate entered the United States in late 2001.

Both cows were born before the United States and Canada began banning brain and spinal cord tissue from cattle feed, which is the primary means by which the ailment is transmitted. The ban, which took effect in August 1997, prohibits feeding such protein to cattle, sheep and goats.

Bovine spongiform encephalopathy, or mad cow disease, is transmitted through such feed, which may contain misshapen proteins known as prions. The disease is associated with a fatal brain-wasting human disorder called variant Creutzfeld-Jakob disease. About 154 people have died of the illness, mostly in Britain. There is no cure, and infected people usually show no symptoms for years.

"The age of the animal is especially important because it is a likely explanation" for the Holstein’s infection, said Ron DeHaven, chief veterinary officer at the Department of Agriculture. "She was born before feed bans were implemented in North America."

U.S. officials are trying to trace the Washington state Holstein to an Alberta farm using DNA tests. But Canada’s top veterinarian said even if such a link is shown, there seems to be no one source of contaminated feed that could have gone to both the Holstein and the Canadian beef cow.

The two infected animals did not come from the same farm, no animal exchanges took place between the farms and feed records do not indicate a common source of contamination, said Brian Evans, Canada’s chief veterinarian. That makes it all the harder for scientists to trace the tainted feed and determine how widespread its use was.

Evans said officials in both countries will be forced to take a closer look at thousands of cattle in the 6- to 8-year-old age range that were born before the feed bans. New surveillance measures will be necessary, he said. DeHaven also indicated that U.S. surveillance probably will be strengthened.

Wherever the infection may have started, it is now a cross-border problem: U.S. and Canadian authorities have repeatedly emphasized that the beef and dairy industries in both countries are tightly integrated.

On Saturday, U.S. officials said that based on an ear tag match, the infected Holstein was brought over the border in August 2001. But the Holstein that came over the border at Eastport, Idaho, was born in April 1997, according to Canadian records. Documents at the Washington state farm, which has been identified as the Sunny Dene Ranch in Mabton, indicated the animal was born around 1999, U.S. officials said after the case came to light on Dec. 23.

Monday, U.S. officials said new records found at the Washington farm placed the age of the Holstein close to the age in the Canadian documents — increasing the likelihood that they were the same animal — and implicating a source of contaminated feed before the safety bans took effect. New records were unearthed by the owner of the Mabton farm following "an extensive search of his records," DeHaven said.

Since there is still some discrepancy between the U.S. and Canadian farm records, officials on both sides agree that a DNA test will be the only conclusive proof that they are talking about the same animal. Samples from the Holstein’s brain, which were used in the test for mad cow disease, will be compared in the next few days with DNA from its father. The bull, Canadian records show, was a Holstein that was widely used in artificial insemination programs.