WASHINGTON (Reuters) - Investigators are searching for a dozen herdmates of the elderly California dairy cow that had mad cow disease, the Agriculture Department said on Friday, with all signs indicating it was a rare spontaneous case of the fatal brain-wasting illness.
Two laboratories associated with the World Organization for Animal Health confirmed the cow had an atypical version of mad cow disease, USDA said. It was the same diagnosis as USDA tests.
USDA said the investigation was moving toward completion. A quarantine has been lifted on the dairy where the latest case originated and on an associated dairy.
USDA announced the discovery on April 24 of the fourth U.S. case since 2003 of mad cow disease, an elderly, lame cow that died on a dairy farm in Tulare County, about 175 miles north of Los Angeles.
The cow was not sent to a packing plant and there was no risk to the food supply.
A review of feed records at the Tulare County dairy found no anomalies and audits of feed suppliers show they complied with safeguards to prevent feed contamination.
Out of several hundred cattle that may have been born at the same time and area as the infected cow, the investigation seeks roughly 10 to 12 that may still be alive and have ownership records that allow tracing. The rest of the birth cohort are no longer alive or otherwise ruled out.
On May 2, USDA said two calves were born to the infected cow in the past two years. One was stillborn. The other was found in another state, was killed and tested negative for mad cow.
Although USDA said the latest case was "atypical," meaning it arose spontaneously, it is USDA practice to search for other offspring or herdmates that might be exposed to the disease although it is not contagious.
Reporting By Charles Abbott