DNA Confirms Infected Cow’s Origin

DNA tests have confirmed that the Holstein found last month to be infected with mad cow disease originated in Alberta, Canada, U.S. Department of Agriculture officials said Tuesday.

The DNA testing on the cow and her offspring, as well as earlier-reported records showing that the cow had been sold by an Alberta farmer disposing of his dairy herd, “makes us confident in the accuracy of this trace-back,” said W. Ron DeHaven, the department’s chief veterinarian.

The confirmation, based on DNA tests at two laboratories -- one in the United States and one in Canada -- leaves unanswered the question of how the cow from a farm in Washington state became infected. Officials will now concentrate on the feed used by the cow’s original owner in Alberta.

Dr. Brian Evans, chief veterinary officer for the Canadian Food Inspection Agency, said on a USDA conference call Tuesday that investigators would also try to determine whether the feed source for the Holstein was the same as that for an Alberta cow diagnosed with mad cow disease in May.

Scientists believe that bovine spongiform encephalopathy, or BSE, the brain-rotting illness commonly known as mad cow disease, can be transmitted to cattle that eat feed containing the remains of infected cows. In the past, leftover parts of slaughtered animals -- including the brain and the spinal cord, which are believed to harbor the source of the infection -- were ground up and used in animal feed.

In 1997, the U.S. and Canada banned the use of the remains of ruminants, or cud-chewing animals, in feed used for cattle, but both North American cows diagnosed with BSE -- the one discovered in Canada in May and the one found in the United States in December -- were born several months before that ban went into effect. The human form of the illness, variant Creutzfeldt-Jakob disease, has been associated with consumption of food made from BSE-infected animals.

Agriculture Secretary Ann M. Veneman announced Dec. 23 that a cow slaughtered Dec. 9 had tested positive for BSE. The cow was tagged for testing because it was a “downer” cow that was unable to walk to slaughter. The cow’s meat products had already been distributed before Veneman’s announcement, primarily to retail outlets in Washington and Oregon.

While officials recalled the meat, it is not known how much was recovered.

Veneman has since announced a series of reforms to bolster U.S. defenses against BSE, including a ban on accepting downer cows for slaughter and a rule that would hold all meat products from an animal tested for disease until results are completed.

But after Tuesday’s announcement of the DNA results confirming the cow’s origin, some producers said the Agriculture Department had moved too slowly to determine the source of the infection.

“They knew the leads pointed back to Canada, and if they had made the announcement immediately, it might have mitigated a great deal of our loss,” said John Lockie, executive director of R-CALF USA, a national association of cattle producers.