By Todd Sperry
(CNN) -- Two farms have been quarantined by
the U.S. Department of Agriculture as the agency continues to investigate last
month's discovery of mad cow disease at a California dairy farm.
Authorities also have launched an
investigation at a calf ranch where the initial infected cow was raised 10
years ago, according to a statement released late Wednesday by the USDA.
Last week, the USDA documented the
fourth confirmed U.S. case of Bovine Spongiform Encephalopathy (BSE) -- a brain
wasting disease affecting cattle -- known commonly as mad cow disease, at a
rendering facility in central California. USDA officials said the cow was never
presented for human consumption and was not a threat.
The farm where the cow was initially
discovered has been under quarantine since the discovery, agriculture officials
said. Wednesday's announcement of a second quarantine involves a farm closely
associated with the dairy where the sick cow was discovered last month, the
USDA said. The agency is still trying to determine if any at-risk cattle are
present at either of the two farms.
Eating contaminated meat or some other
animal products from cattle that have BSE is thought to be the cause of
Creutzfeldt-Jakob disease. The fatal brain disease was blamed for the deaths of
150 people in Britain, where there was an outbreak in the 1980s and 1990s.
In people, symptoms of the disease
include psychiatric and behavioral changes, movement deficits, memory
disturbances and cognitive impairments.
BSE can cause infected animals to
display nervousness or aggression, difficulty in coordination and standing up,
decreased milk production or weight loss.
It is usually transmitted between cows
through the practice of recycling bovine carcasses for meat and bone meal
protein, which is fed to other cattle.
In this case, the Agricultural
Department reported that the cow had a rare form of BSE not likely carried by
contaminated feed.
Since 2004, the USDA has removed the
brain and the spinal column, the parts suspected of causing mad cow disease in
humans, from the food system.
The USDA says that since the discovery
of the infected cow, they have identified 10 different feed suppliers that
delivered animal feed to the farm. Determining if the cow became sick from feed
is an area where investigators are focusing close attention.
Authorities have determined the
infected cow gave birth twice. One calf was stillborn and the other was located
on a farm outside of California. That cow was subsequently euthanized and
tested negative for mad cow disease.
Unlike most other meat-borne illnesses,
such as those caused by E.-coli bacteria, cooking does not kill the infectious
agent that causes mad cow disease.
Consumers who wish to exercise extra
caution can follow the advice presented by the Web-based consumer advocacy group
Consumeraffairs.com, which advises the avoidance of
brains, neck bones and beef cheeks, bone marrow and cuts of beef that are sold
on the bone. The group also says to choose boneless cuts of meat and ground
beef only if it has been ground in the store.
"Evidence shows that our systems
and safeguards to prevent BSE are working, as are similar actions taken by
countries around the world," said John Clifford, the Agriculture
Department's chief veterinarian.
Last year, 29 cases of BSE were
reported worldwide, down 99% from the peak of 37,311 cases in 1992.
"This is directly attributable to
the impact and effectiveness of feed bans as a primary control measure for the
disease," he said last month.
The Agriculture Department confirmed
the first case of mad cow disease in America on December 23, 2003, in a cow
born in Alberta, Canada, in April 1997, only four months before the United
States and Canada began banning the use of brain and spinal cord tissue in cattle
feed.
A second U.S. case was confirmed June
24, 2005, and a third on March 13, 2006.
Courtesy CNN
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