Officials hope the results will help investigators searching for the source of infection, which is most likely contaminated feed the cow ate in Alberta, where the Holstein cow was born in 1997.
To trace the cow’s origins, DNA tests were performed on the cow, on one of its offspring and on the semen from the cow’s sire. Results from those tests and records that show the cow came from a dairy farm in Alberta make the USDA “confident in the accuracy of this traceback,” said Dr. Ron DeHaven, the Agriculture Department’s chief veterinarian.
Brian Evans, a Canadian agriculture official, said results from independent testing at a Canadian lab agreed with the U.S. findings.
Canadian officials had announced last May that a cow in Alberta had been diagnosed with bovine spongiform encephalopathy (BSE) or mad cow disease. Contaminated feed is the most likely way that both cows contracted the disease, but officials said they have not found a common feed source for the two farms.
“We have not at this point got sufficient evidence to make any definitive feed link between the two farms,” Evans said. “They did not buy from a common feed mill. They did not have similar type rations on their farms.”
Evans held out hope of finding the cause of the two cases of the disease and said that the investigation will mean officials will “have to go deeper … back into where materials could have been derived.”
The Canadian Cattlemen’s Association said that while the DNA test results were “disappointing,” Canada was still “a country at minimal risk for BSE according to international guidelines.”
The group also said that an investigation into the first Canadian case of mad cow disease “indicated it would not be unexpected to diagnose a few additional animals with BSE” but that “all the proper precautions are in place to ensure the safety of our food supply.”
In a continuing effort to contain any potential spread of the disease in the United States, the USDA decided Monday to kill a herd of 450 calves because it included one of the infected cow’s offspring.
Officials decided to kill all the calves in the Sunnyside, Wash., herd because the calf born to the sick cow was not tagged and cannot be identified.
“This should just continue to instill additional confidence among consumers,” Mary Beth Lang, spokeswoman for the state Department of Agriculture, told the Associated Press. “The likelihood of any transmission to this calf is very remote … This is an abundance of caution.”
That herd is one of three under quarantine in Washington because of ties to the infected animal. The other herds include cows that may have come from the same Alberta farm. In total, 80 other cows from the infected cow’s heard also came into the United States.
U.S. and Canadian investigators are trying to locate the other animals from the Canadian herd that originally included the infected cow and trace the feed eaten by the sick cow to determine if it contained tissue that carried the disease.
Mad cow disease attacks an animal’s nervous system, eventually eating holes in its brain. It sprang up in Britain in 1986 and spread through countries in Europe and Asia, prompting destruction of whole herds and decimating the European beef industry.
Variant Creutzfeldt-Jakob disease has been linked to over 100 human deaths and is believed to be caused by eating neural tissue, such as brain and spinal cord, from cattle infected with mad cow disease.