Alabama Cow Has Mad Cow Disease
Cow Never Entered the Animal or Human Food Chains, U.S. Official Says
March 13, 2006 -- An Alabama cow has tested positive for bovine spongiform
encephalopathy (BSE), commonly called mad cow disease.
The cow "did not enter the animal or human food chains," says John
Clifford, DVM, chief veterinary officer for the U.S. Department of Agriculture
(USDA), in a statement posted on the USDA's web site. "I want to emphasize
that human and animal health in the United States are protected by a system of
interlocking safeguards, and that we remain very confident in the safety of
U.S. beef," Clifford says.
The cow is the third U.S. cow confirmed to have BSE. It was a
"downer" cow, meaning it couldn't walk before a private veterinarian
euthanized it and sent tissue samples to labs for testing. The BSE confirmation
came after inconclusive results from earlier tests.
Herd of Origin Being Investigated
The USDA is investigating the cow's herd of origin. The cow's exact age
isn't known, but it may have been more than 10 years old and only lived on the
Alabama farm for less than a year, Clifford says.
"Experience worldwide has shown us that it is highly unusual to find BSE
in more than one animal in a herd or in an affected animal's offspring,"
Clifford says. "Nevertheless, all animals of interest will be tested for
The cow's first tests, done at a Georgia lab with a USDA contract, were
inconclusive. So the USDA followed up with two more tests done at the National
Veterinary Services Laboratory in Ames, Iowa.
The first of those follow-up tests came back positive for BSE. The second
test's results aren't in yet. "USDA considers an animal positive for BSE if
either of the two confirmatory tests returns a positive result," Clifford
What Causes Mad Cow Disease?
BSE is a transmissible, slowly progressive, degenerative, and fatal disease
affecting the central nervous system of adult cattle. It was first reported
among cattle in the U.K. in 1986. Researchers believe that the infectious agent
that causes mad cow disease is an abnormal version of a protein called a prion.
For reasons still unknown, this protein becomes altered and destroys nervous
system tissue -- the brain and spinal cord.
Cooking has not been shown to kill the BSE agent, according to information
posted on the USDA's web site. Common methods to eliminate disease-causing
organisms in food, like heat, do not affect prions.
There is no evidence to suggest that milk and dairy products carry the agent
that causes BSE, states the USDA. Prions only seem to live in nervous system
Does Mad Cow Disease Affect Humans?
A human version of mad cow disease called variant Creutzfeldt-Jakob disease
(vCJD) is believed to be caused by eating beef products contaminated with
central nervous system tissue, such as brain and spinal cord, from cattle
infected with mad cow disease.
For this reason, the USDA requires that all brain and spinal cord materials
be removed from high-risk cattle -- older cattle, animals that are unable to
walk, and any animal that shows any signs of a neurological problem. These cow
products do not enter the U.S. food supply. The USDA believes this practice
effectively safeguards U.S. public health from vCJD.