"We are looking at any and all appropriate changes we might make to our BSE surveillance program," Ron DeHaven, chief veterinary officer of the U.S. Department of Agriculture, said during a news briefing updating the mad cow investigation. Mad cow is also known as bovine spongiform encephalopathy or BSE.
Changes being considered include increasing the number of cattle that are screened for the disease and modifying the ban on feeding cattle tissue back to cattle -- a practice that is thought to spread mad cow disease among herds if the feed contains tissue from infected cattle.
DeHaven said the surveillance program in place to date has ensured the safety of the U.S. beef supply, but in light of the case of mad cow found in a cow on a farm in Mabton, Wash., earlier this month, "It's time to relook at that."
Efforts to track down the origin of the cow and about 10,000 pounds of beef that may have contained meat from the infected animal continued on Sunday.
The available information continues to indicate the animal came from Canada, DeHaven said. "We're continuing to work with Canadian officials to verify the trace back," he said, adding that media reports U.S. officials were in disagreement with Canadian authorities about the origins of the animal were unfounded.
"We are not in disagreement with our Canadian colleagues about the data we received," he said. Canadian officials said yesterday it was still too early in the investigation to conclusively determine the animal came from the Alberta province of Canada -- where a case of mad cow was identified in May.
DeHaven said the view is shared by the USDA. Indications about the origin of the animal are preliminary and "still not verified," he said.
However, he went on to say the investigation is focused on tracing down the other 73 head of cattle that came across the U.S border with the infected cow. In addition, U.S. and Canadian authorities are also conducting DNA testing to confirm the origin of the cow, he said.
The age of the animal is still in question. Initially, it was thought to be 4-1/2 years old based on U.S. records, but Canadian records indicate its age is closer to 6 1/2.
USDA authorities initiated a recall of 10,000 pounds of meat that may have contained tissue from the infected cow earlier this week, and efforts to track it down have revealed it went to grocery stores in eight different states and Guam, said Kenneth Petersen from USDA's Food Safety and Inspection Service.
Authorities said yesterday the meat had been distributed to Oregon, Washington, Nevada and California. New information indicates limited amounts also went to Alaska, Montana Hawaii, Idaho and Guam.
Some of the meat may have already been consumed, but Petersen said it was safe. "The recall was initiated out of an abundance of caution," he said. "We remain confident in the safety of these beef products ... and will continue to verify the distribution of all products related to recall."
However, surveys from the USDA's own Food Safety and Inspection Service going as far back as 1997 have found bits of spinal cord -which can carry the mad cow infectious agent - in meat processed by machines called advanced meat recovery systems. The infectious agent, known as a prion, can infect humans and cause a fatal brain-wasting condition called variant Creutzfeldt-Jakob disease.
The spinal tissue was thought to have been introduced into the meat in part due to the routine practice of splitting open the animal's spine during processing. Petersen said the Washington cow's spine had been split open prior to removing it from the carcass.
In 1997, after finding spinal cord tissue in ARM processed beef, the FSIS concluded: "The presence of spinal cord in meat is not expected and cannot be allowed in product produced through AMR systems" due to concerns about transmitting mad cow disease to humans.
The FSIS began to test AMR produced meat for spinal tissue in March of this year after a 2002 survey of 34 establishments producing beef products from AMR systems found that 35 percent of the samples contained spinal cord and other central nervous system-associated tissues such as dorsal root ganglia.
The agency noted in a report released in February spinal cord and dorsal spinal nerve root ganglia "have been identified in the Harvard BSE Risk Assessment (2002) as specific risk materials for bovine spongiform encephalopathy (BSE)."
Regarding changes to the mad cow surveillance program, DeHaven did not elaborate on what types of modifications are being considered for the feed ban.
Feed manufacturing firms have violated the ban since it first went into effect in 1997, and the Food and Drug Administration was sharply criticized for its lack of enforcement of the ban in reports from the General Accounting Office, including one issued just last year.
The FDA said compliance rates are now near 99 percent.
DeHaven said the kinds of changes being considered for mad cow testing include whether the U.S. should increase the number of animals it tests or modify the population of animals it targets for testing.
Critics of the USDA's testing regime have insisted it does not test enough animals to ensure that all the mad cow cases in U.S. herds are detected.
Up until now, the USDA has been reluctant to use the so-called rapid test, which the United Kingdom and other European countries began using after mad cow was first detected there in the 1980s.
The rapid test, which yields results overnight, allows for screening thousands to millions of cattle per year. At present, the USDA, using a slower test called the immunohistochemistry test that can take eight days to produce results, screens only 20,000 cattle out of the more than 30 million slaughtered annually.
Some European countries tested hundreds of thousands of cattle before they detected the disease in their herds and Japan screens every animal slaughtered.
Steve Mitchell is UPI's Medical Correspondent. E-mail email@example.com