FRESNO, Calif. (AP) — The
California dairy cow found to have mad cow disease was very old for a
milk producer and had been euthanized after it became lame and started
lying down, federal officials revealed in their latest update on the
discovery.
The
10-year-old dairy cow, only the fourth ever discovered in the United
States, was found as part of an Agriculture Department program that
tests about 40,000 cows a year for the fatal brain disease. It was
unable to stand before it was killed and sent to a rendering plant's
Hanford, Calif. transfer station. It was one of dozens that underwent
random testing at the transfer site, and the positive results have set
off a federal investigation into the source of the disease.
U.S.
health officials say there is no risk to the food supply. The
California cow was never destined for the meat market, and it developed
"atypical" BSE from a random mutation, something that scientists know
happens occasionally. Somehow, a protein the body normally harbors folds
into an abnormal shape called a prion, setting off a chain reaction of
misfolds that eventually kills brain cells.
A
USDA spokesman says they do not yet know what causes this strain of the
disease. Agriculture officials are investigating, among other things,
whether feed sources might have played a role in the animal contracting
the fatal illness.
The
strain of bovine spongiform encephalopathy that appeared in the UK in
the 1990s and set off a worldwide beef scare was a form caused by cattle
eating rendered protein supplements derived from slaughtered cattle,
including brains and spinal columns, where the disease is harbored.
Scientists know less about the "atypical" strain.
It
"may or may not be related to feed or forage type," said Larry Hawkins,
spokesman for the USDA's Animal and Plant Health Inspection Service in
California. The dairy in question is one of 381 in Tulare County, the
No. 1 dairy county in the nation. Most mega-dairies have computerized
records which would allow investigators to easily track any offspring
the cow had in order to keep up her milk production.
However,
USDA spokesman Matt Herrick said investigators are laboring through
paper records. That fact, combined with the fact that the cow was more
than twice as old as most milk cows in the system, could indicate one of
the region's smaller dairies is the target of the probe. The World
Organization for Animal Health has established protocol for
investigations into cases of bovine spongiform encephalopathy that
includes finding other cows that the Holstein in question was raised
with, tracking down all progeny and determining what she ate.
After
the UK crisis, federal regulations changed to keep brains and spinal
columns in cattle over 30 from being rendered into protein products for
human consumption. In addition, bovine protein is not supposed to be fed
to other bovines.
However,
bovine protein is routinely fed to egg-laying chickens, and the
"litter" from those chickens — chicken excrement and the feed that
spills onto the floor — is collected and rendered back into cattle feed.
Neurodegenerative researchers such as UC San Francisco's Dr. Stanley
Prusiner, who received the 1997 Nobel Prize in Medicine for discovering
prions — the protein associated with BSE — has warned that the US should
ban poultry waste in cattle feed.
Most
dairy cows typically experience declining milk production by age 5 and
are sent to slaughterhouses to be ground into hamburger. The FDA tests
40,000 of the nation's 35 million slaughtered dairy and beef cattle
annually for BSE, targeting animals older than 30 months, when the
disease is more likely to appear. However, there are cases of BSE that
have been detected in cattle as young as 20 months.
"We
are testing .12 percent of the cattle slaughtered," Michael Hansen,
senior scientist at the Consumers Union and a longtime critic of the US
policy regarding mad cow disease. "In Japan they test all cattle over 20
months, in Europe it's all cattle over 24 or 30 months, depending on
the country. They've been able to find sick animals that look healthy
but could have ended up in the food supply."
A
move by a Kansas beef packer in 2006 to voluntarily test all of its
beef so it could label the packages "BSE free," was thwarted by the
USDA, which argued that it would create instability in the market.
Creekstone Farms Premium Beef had challenged the USDA's position that it
held legal authority to control access to the test kits.
In
the current case, the USDA didn't elaborate on the cow's symptoms other
than to say it was "humanely euthanized after it developed lameness and
became recumbent." Outward symptoms of the disease can include
unsteadiness and incoordination. The unidentified Tulare County dairy
where the cow died was not under obligation to report its suspicious
behavior, according to state and federal agriculture officials, because
the symptoms mimic other neurological diseases that can afflict cattle,
said Dr. Richard Breitmeyer, director of the California Animal Health
and Food Safety Laboratory at UC Davis.
"In
reality (mad cow disease) is so rare in this country and there are just
very little in the way of clinical signs specific to BSE alone," said
Breitmeyer, who spent 17 years as California's state veterinarian.
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