FRESNO, California (AP) — Federal agricultural officials who said a California cow died of an atypical form of mad cow disease now are investigating whether feed sources might have played a role in the animal contracting the fatal illness.
Officials said Friday that the dead cow that tested positive for mad cow disease was very old for a milk producer and was exhibiting telltale signs of the illness before it was euthanized.
"We've confirmed it's atypical, and that's just a classification. There is not enough scientific evidence at this point to acknowledge the causes for atypical," said USDA spokesman Matt Herrick.
The strain of bovine spongiform encephalopathy that appeared in the UK in the 1990s and set off a worldwide scare was a form caused by cattle eating rendered protein supplements derived from other cattle. Scientists know less about the "atypical" strain.
It "may or may not be related to feed or forage type," said Larry Hawkins, spokesman for the USDA's Animal and Plant Health Inspection Service in California.
The 10 1/2-year-old cow was unable to stand before it was killed and sent to a rendering plant's Hanford, California transfer station.
It was one of dozens that underwent random testing at the transfer site, and the positive results have set off a federal investigation into the source of the neurological disease.
The dairy in question is one of 381 in Tulare County, the No. 1 dairy county in the nation. Most mega-dairies have computerized records which would allow investigators to easily track any offspring the hold cow had in order to keep up her milk production.
However Herrick said investigators are laboring through paper records. That fact, combined with the fact that the cow was twice as old as most milk cows in the system, could indicate one of the region's smaller dairies is the target of the probe.
The World Organization for Animal Health has established protocol for investigations into cases of bovine spongiform encephalopathy that includes finding other cows that the Holstein in question was raised with, tracking down all progeny and determining what she ate.
After the UK crisis, federal regulations changed to keep brains and spinal columns in cattle over 30 from being rendered into protein products for human consumption. In addition, bovines protein is not supposed to be fed to other bovines.
However, bovine protein is routinely fed to egg-laying chickens, and the "litter" from those chickens — chicken excrement and the spilled feed — is collected and rendered back into cattle feed. Scientists such as Dr. Stanley Pruisiner, who received the Nobel Prize for his work into the study of prions — the protein associated with BSE — has warned that the US should ban poultry waste in cattle feed.
The classic cases of BSE in the UK that set off a worldwide meat panic in the 1990s came from cattle that were fed protein supplements that were derived from the rendered carcasses of other bovines. Subsequently brains and spinal columns in cattle over 30 months cannot be rendered, but critics of the US food safety system point out that there have been cases diagnosed in cattle as young as 20 months.
Most dairy cows typically experience declining milk production by age 5 and are sent to slaughterhouses to be ground into hamburger. The FDA targets its 40,000 BSE tests conducted annually on the nation's 35 million slaughtered cattle at animals older than 30 months, when the disease is more likely to appear, though Hansen argues that BSE has been detected in cattle as young as 20 months.
"We are testing .12 percent of the cattle slaughtered," Michael Hansen, senior scientist at the Consumers Union and a longtime critic of the US policy regarding mad cow disease. "In Japan they test all cattle over 20 months, in Europe it's all cattle over 24 or 30 months, depending on the country. They've been able to find sick animals that look healthy but could have ended up in the food supply."
The USDA didn't elaborate on the cow's symptoms other than to say it was "humanely euthanized after it developed lameness and became recumbent." Outward symptoms of the disease can include unsteadiness and incoordination.
We don't know for a certainty what causes the atypical strain of BSE...may or not be related to feed or forage type," wrote USDA spokesman Larry Hawkins in an email to the Associated Press.
The unidentified Tulare County dairy where the cow died was not under obligation to report its suspicious behavior, according to state and federal agriculture officials, because the symptoms mimic other neurological diseases that can afflict cattle. The episode put a spotlight on the federal system for detecting mad cow disease in the nation's estimated 90 million beef and milk cattle.
"Regardless of whether it was down or not, the U.S. testing system is completely inadequate," said Dr. Michael Hansen, chief scientist at the Consumers' Union.
The brain wasting disease known as bovine spongiform encephalopathy, which causes unsteadiness, aggressive behavior and incoordination in cows in the weeks before death, can mimic other neurological conditions that don't impact humans, said Dr. Richard Breitmeyer, director of the California Animal Health and Food Safety Laboratory at UC Davis.
"In reality (mad cow disease) is so rare in this country and there are just very little in the way of clinical signs specific to BSE alone," said Breitmeyer, who spent xx years as California's state veterinarian.