Yesterday, the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed the nation’s fourth case of bovine spongiform encephalopathy (BSE), or more commonly known as mad cow disease, in a dairy cow from central California. The infected cow was found as part of the USDA’s ongoing BSE surveillance program which samples about 40,000 cows a year in high-risk cattle populations where the disease is most likely to be found.

BSE is a progressive neurological disease among cattle that results in degeneration of their central nervous system and is ultimately fatal. There is strong epidemiologic and laboratory evidence to suggest that there is a connection between a human disease called variant Creutzfeldt-Jakob disease (vCJD) and the consumption of beef tainted by BSE.

The first incidence of BSE in the U.S. was detected on December 23, 2003 in a cow that had been imported from Canada to Washington state. Ten years earlier, in 1993, the United Kingdom experienced a severe BSE epidemic that affected thousands of cows throughout the country and precipitated worldwide concern over the safety of the beef supply. Years later, in the wake of the United Kingdom’s BSE epizootic, that fear persisted among consumers and the global food industry. As a result, when the U.S. detected its first of only four cases of BSE in 2003, beef exports reportedly plummeted the following year. It took several years for the industry to fully recover from that incident.

Now, in an effort to quell those same concerns, USDA Chief Veterinary Officer John Clifford issued a statement assuring consumers and global importers that meat from the California dairy cow did not enter the food chain. “It was never presented for slaughter for human consumption, so at no time presented a risk to the food supply or human health. Additionally, milk does not transmit BSE,” he stated.

Clifford further explained that the U.S. has a comprehensive system in place – including a mammalian feed ban, removal of specified risk materials, and vigorous surveillance – to ensure that beef and beef products are safe for human consumption. He concluded that this finding should not affect U.S. beef exports or its BSE status as determined by the World Organization for Animal Health (OIE).

Yet, despite assurances that the infected cow poses no risk to the human food supply, lingering fears over BSE have already caused live cattle futures to drop on the Chicago Mercantile Exchange to their lowest point in seven months. In addition, although major U.S. trading partners, including Mexico, Japan, Canada and the European Union, indicated that they will continue to import U.S. beef, two large South Korean retailers have removed U.S. beef from their stores. This comes at a hard time for the beef industry in light of the recent negative publicity surrounding lean finely textured beef, or what has become notoriously referred to as “pink slime”.

Currently, the carcass of the animal is being held at a rendering facility in California where it will be destroyed. USDA officials have sent samples taken from the infected cow to laboratories in Canada and the United Kingdom for final confirmation. The agency is continuing its investigation into how exactly the animal could have become infected.