The U.S. Department of Agriculture and the Food and Drug Administration are attempting to trace down the birth herd of the cow to help officials determine how it contracted the disease and whether other animals also may have been infected.
Confirmed positive for the disease on Christmas day, the approximately 4-year-old infected cow first appeared on a farm in Mabton, Wash., in October of 2001. But beyond that, records are less certain.
Authorities think the cow might have been purchased either from a livestock market or a dairy facility close to Mabton, but so far they have been unable to turn up any definitive leads. It could have originated in Canada, elsewhere in Washington or even other states.
"If we're lucky, we could know something in a matter of a day or two," Ron DeHaven, USDA's chief veterinary officer, said during a news briefing. He noted, however, it took several weeks for Canadian authorities to track down the origin of their first domestic case of mad cow, which was reported last May.
"It might not be a matter of days ... it could be a matter of weeks or months," Dehaven said. "We might not be able to absolutely determine (the origin) at all," he said, adding later it is "no doubt going to be a very complicated and complex investigation."
Some of the leads suggest the animal came from Canada and some indicate it could have originated in other states, DeHaven said. "Potentially many states could be involved."
The investigation was launched just three days ago and so far USDA officials have found the infected cow gave birth to three calves before it was slaughtered on Dec. 9. The disease usually is spread through infected feed and it is unlikely the infected cow would have passed it on to her offspring, DeHaven said.
To be on the safe side, however, the USDA has quarantined the facilities where the remaining calves -- one died at birth in 2001 -- currently reside.
One calf -- born just prior to the infected cow's slaughter -- was sold to a bull calf feeding operation in Sunnyside, Wash. "No animals will be leaving those premises," DeHaven said, adding the quarantine was imposed on Dec. 24.
The other calf remains on the Mabton farm where the infected animal resided. That facility was placed under quarantine earlier this week.
Efforts to find the source of infection also could come up empty, said Dr. Stephen Sundlof, director of the FDA's Center for Veterinary Medicine.
The most likely source of infection in this case is feed comprised of tissue from other infected cattle. This feed practice is banned in the United States, but between 1999 and 2001 -- when the cow is thought to have been infected -- many firms violated the practice and indeed fed cattle tissue to cows.
"It's going to be a matter of trying to determine where this animal may have gotten contaminated feed," Sundlof said. The average incubation period from the time of exposure to the development of symptoms is about four-to-five years, "so it can be difficult to trace back where the feed originated," he said. "It's not something people keep real precise records of," so it "may not be possible" to determine the origin of the infected feed," he said.
Sundlof said the compliance rate with the feed ban is now 99 percent and all of the firms located in Washington are in compliance. However, he added, in reference to problems with compliance in previous years, "We assume the compliance rate was less than 100 percent" when the animal was infected.
On the human side, the USDA is continuing its efforts to recall all the infected beef that could have made its way into the food supply. Humans can contract a fatal condition known as variant Creutzfeldt-Jakob disease from eating meat from cows infected with mad cow disorder.
The agency issued a recall of approximately 10,000 pounds of beef that could have contained meat from the infected animal two days ago. Two Oregon firms -- Willamette Valley Meat in Portland, and Interstate Meat Distributors in Clackamas -- processed the meat and began shipping it out to their customers 13 days ago on Dec. 13.
Both firms have sent out notices informing their customers the meat has been recalled, but the USDA is uncertain if any product has been recovered, said Kenneth Petersen of the agency's Food Safety and Inspection Service.
Petersen said he expects some customers to begin returning the meat today. He did not cite the names of the companies that might have received the meat and said his agency still is in the process of collecting information pertaining to the distribution of the beef.
Steve Mitchell is UPI's Medical Correspondent. E-mail firstname.lastname@example.org