The occasional case of mad cow disease appearing in cattle can still happen even though the U.S. beef industry is well-regulated, according to Purdue researchers.
On Tuesday, the USDA confirmed a dairy cow in California was infected with mad cow disease, technically known as bovine spongiform encephalopathy. This is the first case of the disease in the U.S. since 2006.
But this case of mad cow is more unusual than others, according to Purdue veterinary scientist Mark Hilton.
“I know it’s not the same kind that happened in Great Britain,” Hilton said.
Hilton referred to the thousands of cases of the disease reported in Great Britain during the ‘90s. Those cases were traced back to the feed the cattle were eating. According to Hilton, it was common practice throughout the farm industry to render the carcasses of dead cows into feed for living ones. Researchers traced a prion, a type of protein, that caused the disease in cows once they consumed it.
This practice has been banned in the U.S. for 15 years, which is why Hilton thinks the California case is an isolated issue. He said this type of mad cow disease occurred from a gene mutation that was unrelated to consuming the type of prion that the cattle in Britain did.
“These type of things have the potential to happen from time to time,” Hilton said. “You could say there’s a one in a million chance of this happening, which is why we have numerous safeguards in place.”
Those safeguards include regular cattle testing. According to Stephen Hooser, director of the Animal Disease Diagnostic Laboratory, the USDA randomly tests about 40,000 cattle per year. That’s a small percentage of the 34 million cattle slaughtered in the U.S. in 2011. However, Hooser said the testing is working well, and he credited the regulation with detecting the California case.
“That means the policy is working,” Hooser said. “We conduct surveillance and systematically remove cows that appear to be diseased.”
Hooser said about a million cows have been tested since this program has started.
“All cows tested that were diseased were found on the West Coast,” Hooser said. “There has never been a case in Indiana or anywhere in the Midwest.”
If a cow is infected, most of the disease is located in the brain and nervous tissues. Hooser said these parts of the cow are not sold for human consumption. He emphasized humans cannot contract the disease through drinking milk or eating a cut of steak from a potentially infected cow.