Though the investigation suggests the cow originally came from Canada, it is becoming more likely the source of infection never will be known.
Canadian officials have yet to track down the source of contaminated cattle feed they suspect caused the country's first domestic case of mad cow disease in May and it appears unlikely they will have better luck tracing the source of infection for the U.S. cow, which appears to have come into the United States in 2001.
When Canadian officials concluded the investigation of their mad cow case in July, they acknowledged it probably had contracted the deadly disease from eating feed contaminated by the tissue from another cow carrying the illness.
It is impossible to determine, officials said, whether any other cattle consumed the same feed and became infected, or whether meat from an infected animal entered the human food supply -- in either Canada or the United States.
Such uncertainty raises serious concerns because humans can contract an agonizing and always fatal brain condition, known as variant Creutzfeldt-Jakob disease, from consuming the mad cow pathogen.
In the latter part of the 20th century, the beef industries in Europe, the United States and elsewhere began augmenting cattle feed with protein-bearing tissues from various animals -- an unnatural diet for cows, whose multiple stomachs are designed to digest plants. Routinely, along with plant fiber, the feed contained concoctions of roadkill, euthanized dogs and cats from animal shelters and the head, intestines, hooves, bones and blood of cattle, according to Howard Lyman, a former cattle farmer and feedlot operator who is now an organic farming activist.
Ranchers often send sick and dead animals straight to a rendering facility, Lyman told UPI. "You couldn't find (a cow carcass) that wasn't too rotten, cancerous or putrid they wouldn't grind it up and turn it into feed," he said.
The U.S. Food and Drug Administration has said all non-edible tissues from the infected U.S. cow that went to rendering have been located and did not enter commercial distribution.
In 1997, U.S. and Canadian regulatory agencies prohibited cattle tissues from being included in cow feed because of fears it could spread mad cow disease among the herds. The timeline is important. Canadian officials maintain the infected Alberta cow -- which was estimated to be 6-to-8 years old at the time of its slaughter -- had eaten contaminated feed before the ban was imposed and became infected.
The U.S. mad cow, which resided on a farm in Mabton, Wash., is thought to have been about 6 years old when it was slaughtered for human consumption on Dec. 9. If the age of the animal is accurate, this means it may have been born around the time Canada put its feed ban in place. It might even have become infected after the ban began, which raises questions about the lax enforcement of the ban and the possibility other animals were infected in the same manner.
"It cannot be determined whether the contaminated (feed) was of imported or domestic origin," an international team of experts who reviewed the Canadian investigation into the mad cow case concluded in their report. The team added: "Neither can past exposure of other cattle to contaminated feed be discounted" and recommended "the need to address the risk that (mad cow disease) is present in the Canadian herd and beyond."
The possibility of additional mad cow cases worries consumer groups.
"There's a strong possibility that more than one cow consumed the same feed," Dr. Peter Lurie, deputy director of Public Citizen's Health Research Group, a watchdog organization in Washington, told UPI. "One simply can't complacently assume this one cow that was detected was the only cow infected," said Lurie, who has followed the mad cow situation in the United States for years and has conducted several investigations into how the government conducts screenings for the disease.
"If more than one cow became infected (in Canada), it is likely that they were slaughtered before they developed symptoms," he said. Lurie noted cows might not show symptoms for several years, yet often are slaughtered at age 2. This raises the possibility the infected cattle "could have been consumed by human beings (or) could have been fed to other cattle," he said.
Lurie noted the disease still could be "percolating in the Canadian herd," as well as American herds because before U.S. officials shut the border to Canadian beef and cattle products in May, the two countries largely shared an open border, with both feed and live cattle going back and forth.
In July, U.S. officials said the infected cattle feed likely came from Canada or a country in Europe.
"Either the feed came from a country where (mad cow disease) was prevalent or it came from a (mad cow-infected) cow in Canada and somehow got into cattle feed," Stephen Sundlof, director of the Food and Drug Administration's Center for Veterinary Medicine, told UPI.
Sundlof added, however, the circumstances are "nebulous" and it might be impossible to determine exactly where the infected feed originated. "There was a lot of flow back and forth across the border of feed ingredients," he said. "In all likelihood, we'll never be able to trace back the exact source of feed the animal was originally exposed to."
Although it is early in the investigation of the Washington mad cow, Sundlof has said the same thing about that case, noting it is difficult to determine after the fact which cattle consumed what feed.
That thought was echoed by the American Feed Industry Association, a trade group representing firms that manufacture animal feed.
"We can speculate all day long but we will never know where the case came from," Richard Sellers, AFIA's vice president, told UPI in July, commenting on the Canadian case. Many feed manufacturers had facilities in both the United States and Canada and treated the border between the two countries "like a state border," with feed products "going back and forth," he said.
Just six months ago, the National Cattlemen's Beef Association said it had no concerns about the mad cow-infected feed potentially originating from, or being given to, U.S. herds. The NCBA also noted at the time no case of mad cow disease had ever been detected in U.S. cattle.
"More important, we're very confident in the tools that are in place (such as the feed ban) to prevent it from spreading should it ever happen here," Kim Essex, spokeswoman for the association, told UPI. "It's a highly effective system," Essex said.
Despite that assessment, federal officials said Sunday, in light of the first case of the disease in U.S. herds, they were considering modifying their mad cow prevention programs, including making changes to the feed ban. Its enforcement is deemed critical to prevent the spread of mad cow disease among herds because that is how the disease is suspected to have amplified in the United Kingdom in the mid-1980s.
At the time, U.K. ranchers unwittingly were incorporating infected-cows into their cattle feed and giving it to their herds. Ultimately, approximately 180,000 cattle contracted the disease and more than 100 people contracted variant CJD after eating tainted beef.
Lurie noted the FDA has been lax in its enforcement of the U.S. feed ban and thus the potential has existed for American cattle to become infected if the contaminated feed source originated in the United States or was imported from Canada.
A 2002 report from the General Accounting Office supported Lurie's claim. The report slammed the FDA for its failure to enforce the feed ban. The GAO said it had "identified some noncompliant (feed manufacturing) firms that had not been reinspected for two or more years and instances when no enforcement action had occurred even though the firms had been found noncompliant on multiple inspections."
The report concluded: "FDA's data on inspections are severely flawed and, as a result, FDA does not know the full extent of industry compliance."
Sundlof said those problems have been corrected and now the compliance rate is 99 percent. This means "somewhere around 12 out of 1,500 establishments that qualify for this kind of inspection program are not in compliance," he admitted in July.
Sundlof now says only two firms are not in compliance.
Lurie countered that violations in the past are the primary concern.
"It doesn't matter what happens now, it matters what happened years ago," he said, because that is when companies could have been incorporating mad cow infected tissue into cattle feed and spreading the disease among the herds.
In July, the FDA took legal action against X-Cel Feeds Inc., of Tacoma, Wash., a feed manufacturer, because the firm had violated the feed ban and had incorporated cattle tissue into cattle feed. However, X-Cel's violations go back some 14 years to 1989 and FDA never moved to shut down operations or warn ranchers the feed contained improper material.
Spreading the disease among the herds is a much bigger concern than if a few infected cattle were consumed by humans, Lurie warned. If only a few diseased animals made their way to the human food supply, it probably would strike only a few people at most, he said. "The bigger problem from a public health point of view is when infection resides in the cattle population and there's ineffective enforcement of the feed ban ... Then you can amplify infection and then there's more people who could be consuming it," he said.
The disease has had ample opportunity to spread among U.S. herds because the feed ban was not enforced effectively for six years, he said, adding there are 6,000-8,000 unregistered feed mills that are not regulated by the FDA.
In July, the FDA announced it is considering improving its system for regulating animal feed. In a notice published in the Federal Register, the agency said it is mulling the possibility of developing "a safety program to effectively minimize the hazards to public health, both human and animal health, posed by animal feed products." One focus of the risks the safety program would be mad cow disease.
However, Lyman, who was raised on a dairy farm and ran a feedlot operation for 20 years, said most ranchers ignore regulations put forth by the FDA and other regulatory agencies. "Unless you're in this business, you have no idea how ineffectual the (U.S. Department of Agriculture) and FDA are," he said. "Ranchers basically do whatever they want to do," because "the consequences of getting caught are one in a million and if you do get caught the consequences are a stern letter (from the agencies)."
Dr. Robert Hills with Health Canada, which enforces the country's health regulations, said it may be impossible to trace the source of the infected feed that gave rise to their first case in May.
But Hills maintained the evidence to date suggests the Alberta cow was infected prior to 1997, when the government banned cow tissue from being included in feed for other cattle. This means the 6-8 year old cow would have had to have been infected very early on in its life.
Lurie called this idea "ridiculous." The animal lived most of its life in the post-feed ban period than in the pre-feed ban period so it is more likely the animal became infected after 1997, he said.
If so, it raises concerns about how well the feed ban was enforced in Canada. Sergio Tolusso, feed program coordinator at the Canadian Food Inspection Agency, told UPI "in some cases" firms were found to be in violation of the ban. Tolusso said for 2001-2002, about 97 percent of Canada's 600 commercial feed manufacturers and 28 rendering plants were in compliance with the ban. For 1999 and 2000, compliance was 100 percent. But for the period from 1997 to 1999, compliance rates are unavailable, he said. The ban went into effect in the summer of 1997, but the agency "didn't really get geared up to doing inspections" until the following year and officials did not begin doing routine inspections until 1999, he said.
Canadian officials said they have not detected any additional mad cow cases but Hills said the investigation into the Alberta cow revealed "there is some potential for ruminant material (tissues from cows, goats and sheep) to be fed to ruminants but that's at the farm level," not at the feed manufacturer level.
Nevertheless, such practices constitute a violation of the feed ban and therefore entail risk for spreading and amplifying the disease among cattle, some of which, no doubt, were consumed by humans.
Steve Mitchell is UPI's Medical Correspondent. E-mail firstname.lastname@example.org