By Stephanie Schupska
University of Georgia
“We’re not dealing with something like your normal virus or bacteria that would be spread from animal to animal,” said Ronnie Silcox, an animal and dairy science professor in the UGA College of Agricultural and Environmental Sciences. “We’re dealing with something that’s spread through feed.”
On March 13, the U.S. Department of Agriculture announced a positive bovine spongiform encephalopathy test result from a cow sampled on an Alabama farm.
BSE, also known as mad cow disease, is a degenerative brain disease. “Cows will lose coordination,” Silcox said. “They act crazy. That’s where the term ‘mad cow’ came from.”
The human variant, called Creutzfeldt-Jakob disease, has been diagnosed in only 150 humans worldwide, none of whom were from the United States.
The attending veterinarian said the Alabama cow may have been more than 10 years old. If so, it was old enough to be eating before a 1997 U.S. Food and Drug Administration ban on ruminant- to-ruminant feeding practices took effect.
“We have such an incredibly low incidence of BSE in the United States,” Silcox said. “In Great Britain, where they’ve had the disease since the 1980s, their very rapid spread of the disease came from feeding meat and bone meal from infected cows to healthy cows.”
On Wednesday, March 15, Japan reported its 23rd case of mad cow disease with a positive test on a 5-year-old Holstein bull. The country’s first case was discovered in 2001, and since then, Japan has tested every domestically slaughtered cow entering the market, according to the Associated Press.
In 1997, the U.S. banned the practice of feeding meat and bone meal back to cattle. The feed ban, according to the USDA, has broken the cycle of BSE.
The average age of a beef cow is 5 to 6, Silcox said. “Over 10 years is fairly old,” he said. After a cow consumes a BSE agent, it takes four to five years for the disease to develop.
When the USDA suspected the Alabama cow could have BSE, they sent samples to the University of Georgia for a rapid test run. The test provided inconclusive results.
“Under USDA testing protocols, surveillance samples are sent to contract laboratories for screening tests,” said USDA Chief Veterinary Officer John Clifford. “If the sample is found to be inconclusive on the screening test, it is then shipped to our National Veterinary Services Laboratories in Ames, Iowa, for an additional rapid test and two confirmatory tests. ... USDA considers an animal positive for BSE if either of the two confirmatory tests returns a positive result.”
Silcox and other cattle experts have been dealing with BSE in the U.S. since December 2003.
“There’s been a lot of testing going on, and this is the third case that’s come up,” he said. “So it’s not a new issue. In all the testing USDA has done, we’ve only detected three cases. It’s more of an indication that we don’t have a high level of the disease.”
The first infected animal was a Washington state dairy cow that was born in Canada. The second was found in June 2005 in a cow born and raised in Texas. The USDA is still trying to determine where the Alabama cow originated. It had been on its most recent farm for less than a year, Clifford said.
(Stephanie Schupska is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)