WASHINGTON – For the fourth time since December 2003, a case of bovine spongiform encephalopathy (BSE) has been discovered in a cow in the United States. The US Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) confirmed the fourth US case of BSE in a dairy cow at a California-based rendering facility, John Clifford, USDA chief veterinary officer announced in a statement on April 24.

“The carcass of the animal is being held under state authority at a rendering facility in California and will be destroyed,” Clifford said. “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.”

Clifford said samples taken from the infected cow were tested at USDA’s National Veterinary Services Laboratory in Ames, Iowa. The cow tested positive for atypical BSE, which is a very rare form of the disease not generally associated with an animal eating infected feed, he added.

"We are sharing our laboratory results with international animal health reference laboratories in Canada and England, which have official World Animal Health (OIE) reference labs,” Clifford said. “These labs have extensive experience diagnosing atypical BSE and will review our confirmation of this form of the disease.

“In addition, we will be conducting a comprehensive epidemiological investigation in conjunction with California animal and public health officials and the FDA,” he added.

US cattle futures began the session trading unevenly, but plunged as rumors began to spread about the BSE discovery. By the end of the trading session, live cattle futures fell 3 cents, or their exchange-imposed one-day limit for price movements, to close at 1.11680 per lb. in trading on the Chicago Mercantile Exchange, according to reports from Dow Jones and other financial news media.

This is the fourth confirmed case of BSE in the US. The first known case occurred in December 2003 after an infected Holstein cow was discovered in Washington state, but traceback revealed it had been imported from Canada in August 2001.

A second case was confirmed in a cow in Texas in June 2005 and was the first endemic case of BSE in the US, according to CDC. The third case was in March 2006, when USDA confirmed BSE in a downer cow that was on a farm in Alabama.

Tom Talbot, chairman of the National Cattlemen’s Beef Association’s cattle health and well-being committee said the bottom line is that all US beef is safe.

“USDA’s ongoing BSE surveillance program tests approximately 40,000 high-risk cattle annually, bringing the total of tested animals to more than 1 million since the program began,” he said. “We commend USDA and animal health experts for effectively identifying and eliminating the potential risks associated with BSE.”

Clifford said the BSE case should not affect US trade and that the detection does not affect the country’s status as determined by the OIE. In his statement, Clifford outlined the safeguards USDA has in place to protect animal and human health against BSE infection.

• USDA bans on specified risk materials, or SRMs, from the food supply. SRMs are parts of the animal that are most likely to contain the BSE agent if it is present in an animal.

• USDA also bans all non-ambulatory (sometimes called "downer") cattle from entering the human food chain.

• For animal health, the Food and Drug Administration (FDA) ban on ruminant material in cattle feed prevents the spread of the disease in the cattle herd.

Clifford said the safeguards are working in the US and abroad— in 2011, there were 29 worldwide cases of BSE, a dramatic decline and 99 percent reduction since the peak in 1992 of 37,311 cases. The decline in BSE cases is directly attributable to the impact and effectiveness of feed bans as a primary control measure for the disease, he said.

"USDA remains confident in the health of the national herd and the safety of beef and dairy products,” Clifford said. “As the epidemiological investigation progresses, USDA will continue to communicate findings in a timely and transparent manner."