updated 1/14/2004 5:28:10 PM ET 2004-01-14T22:28:10

When investigators went to the Alberta, Canada, farm of Wayne and Shirley Forsberg, the couple’s remarkably simple records made it easy to prove they raised the Holstein that brought the first known case of mad cow disease into the United States.

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But investigators are having far more trouble finding the scores of other animals from the Forsberg ranch that came into the United States with the diseased cow.

Three weeks after the infected animal’s discovery at a Mabton, Wash., farm, officials have located only 20 of the 81 cows they are looking for.

That is because finding each cow requires a painstaking search that is sort of a bovine cross between “CSI” and “Without a Trace.”

“It’s a paper trail. We look at import documents, health certificates, farmer sales and shipping orders,” said Jim Rogers, a spokesman for the U.S. Department of Agriculture in Washington, D.C.

There are also interviews with ranchers, shippers, feedlot operators and anyone else who may have come across the animals. And there is DNA testing on calves to determine whether they were offspring of the diseased cow.

The USDA has about 70 people working on this bovine missing-persons case.

National electronic ID system created
The scare already has prompted the USDA to speed creation of a national electronic identification system that would track animals as they move from fields to feedlots to supermarkets. It would enable officials to respond faster to an outbreak of mad cow or other animal-borne illnesses.

Mad cow disease, or bovine spongiform encephalopathy, eats holes in the brains of cattle and is incurable. Scientists believe humans can develop a brain-wasting illness, variant Creutzfeldt-Jakob disease, from eating beef from diseased cattle.

Locating all the cows from the Forsberg herd is key to ensuring mad cow disease does not spread to humans. It also helps reduce the number of cows that have to be destroyed as a precaution.

In fact, just to be safe, U.S. authorities so far have destroyed or marked for destruction more than 570 head of cattle, either because they came from the Canadian farm, might have come from the farm, or might have been born to an infected cow from the farm.

The scare began with a single diseased cow discovered at the Sunny Dene Ranch in Mabton. It was traced immediately back to the Forsbergs’ ranch near Edmonton because it still had a Canadian ear tag. Such tags are not required in the United States.

The Forsbergs’ record-keeping was thorough, if crude.

“We had a little calendar in the barn where we wrote everything down,” Shirley Forsberg recalled last week. The calendars dated back to 1965, when the couple started farming, and listed the birth of calves and other relevant information.

Those records showed that the infected cow was born in 1997, shortly before the United States and Canada banned the use of cattle feed made from the ground-up tissue of other livestock. Such feed is believed to spread mad cow disease.

The infected Holstein remained in Alberta until the Forsbergs retired and sold their herd in 2001. A group of 81 or 82 animals from the ranch was shipped to the United States, crossing the border at Oroville, Wash., on Sept. 4, 2001.

The Forsbergs had to obtain a health certificate to export the animals, which were inspected and given ear tags.

How cows are traced
Investigators tracking those 81 animals found several more at the Mabton ranch and at farms in Quincy, Wash., and Mattawa, Wash. But the rest are unaccounted for.

Nancy Roberts, acting USDA veterinarian for New Jersey, is not involved in the search, but said all tracebacks are essentially the same.

Officials begin by looking for any tags, tattoos, brands or other distinguishing characteristics. There are health certificates required for imported cattle into the United States, plus sales records kept by buyers and sellers.

Then there are the interviews with people who may have come across the animal. One problem is that anything they say could include errors caused by faulty memories or jumbled ID numbers.

“A lot of what we do in tracebacks is based on memory,” Roberts said. “You can have recall errors.”

Despite the obstacles, such traces generally end in success and have been instrumental in the near eradication of brucellosis and tuberculosis in cattle, Roberts said.

© 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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