The first new case of mad cow disease in the U.S. since 2006 was discovered in a dairy cow in California on Tuesday. The infected cow, the fourth ever discovered in the U.S., was found as part of an Agriculture Department surveillance program that tests about 40,000 cows a year for the fatal brain disease.
Mad cow disease, or Bovine Spongiform Encephalopathy (BSE), is a progressive neurological disease that affects cattle. Research indicates that a mutated prion protein infects the central nervous system of cattle, causing a spongy deterioration of both their brain and spinal cord. This neurologic deterioration causes the cow to exhibit behavioral changes, lose control of its muscles and eventually its ability to walk.
Cows, which are naturally herbivores, become infected when they are fed the remains of other infected cattle in the form of meat and bone meal, causing the infectious prion to spread. BSE was first discovered in 1993 in Britain, where a majority of the cases worldwide have been discovered. The cases that afflicted England in the 1990s were caused by livestock being routinely fed protein supplements that contained cow brain and spinal tissue.
BSE is a public health concern because it can be transferred to the human population, most likely through the consumption of food containing ingredients derived from BSE-infected cattle. Consumption of an infected cow’s milk does not transmit BSE.
When a human is infected with this prion, the disease is called variant Creutzfeld-Jakob Disease (vCJD), which is also marked by neurologic degeneration and behavioral changes. CJD is not contagious among humans. There have been a small number of cases of vCJD confirmed in people living in the United States, but the disease was contracted by eating meat from Britain and Saudi Arabia, according to the Centers for Disease Control and Prevention.
Officials say that the cow found in California was an atypical case of BSE, meaning that the cow did not get BSE from eating infected cattle feed, but rather from a random genetic mutation. Of the 3 infected cows found in the U.S. since 2003, two were also shown to have atypical varieties of the disease derived, most likely, from genetic mutations.
In the wake of the British outbreak, the U.S. intensified precautions to keep BSE out of U.S. cattle and the food supply. In a statement released Tuesday by U.S. Secretary of Agriculture, Tom Vilsack, the safety of the U.S. food supply was confirmed.
"The beef and dairy in the American food supply is safe and USDA remains confident in the health of U.S. cattle. The systems and safeguards in place to protect animal and human health worked as planned to identify this case quickly, and will ensure that it presents no risk to the food supply or to human health. USDA has no reason to believe that any other U.S. animals are currently affected, but we will remain vigilant and committed to the safeguards in place," said Vilsack.
While there are no risks to the U.S. food supply at this time, there are several precautions that consumers can take. Only buy beef from a trusted source and know its country of origin. Ensure that the animals are not fed animal by-products, such as meat and bone meal. Consider purchasing grass-fed beef-since these animals are pastured-raised, there is no possibility that they consumed animal tissue. Safer still, eliminate red meat from your diet completely. Not only will this remove your risk of vCJD, but may also decrease your risk of heart disease and certain cancers.
For more information about BSE, visit http://www.cdc.gov/ncidod/dvrd/bse/