A week into the first U.S. mad cow disease scare that started with a single Holstein cow from a Mabton dairy and officials still haven't decided the fate of the 4,000 cows on the dairy or the additional 400 bull calves that are in a Sunnyside feeding operation.
Both the dairy and the calf feeding operation were quarantined last week after the first case of bovine spongiform encephalopathy (BSE) was found.
The dairy was home to the infected cow and the bull calf feeding operation is where her recently born calf was sent shortly after birth.
According to Anna Cherry, spokesperson for the Animal and Plant Health Inspection Service, a part of the USDA, investigators are still looking at options at both sites and talking with owners of the operations.
"If they can't identify the specific calf, which is what I understand is the issue, they may have to depopulate the herd, but there has been no decision made at this time," said Cherry.
She said investigators want to make sure all options are exhausted before cattle are destroyed.
The investigation continues into the origin of the infected cow. Monday morning, Dr. Ron DeHaven, chief veterinary officer for the United States Department of Agriculture, announced that additional records obtained by the infected Holstein's owner showed the cow as an older cow than originally thought. The cow is now believed to be 6-1/2 years old, born in April of 1997, just months before the feed ban went into effect in North America. DeHaven added that the chief line of investigation they are following maintains the cow came from Canada. DNA testing will confirm if the infected cow really was one of the 74 that came from Canada in August of 2001.
DeHaven said they are also seeking out the 73 other cows that are believed to have been imported from the same farm into the United States.
"While reviewing records we have also determined that an additional eight animals from the same herd in Canada were also shipped to the United States, so now we are tracing the location of all 81 animals," said DeHaven.
Even though only one of the cows was found positive for BSE, DeHaven said because of precautionary measures, the United States remains at very low risk. He said there is nothing to indicate the other cows were infected with the disease.
"We can't pinpoint the exact time at which the animal may have consumed contaminated feed," said Dr. Stephen Sundlof of the Food and Drug Administration. "Feed is purchased from a number of different outlets, and even those outlets receive their materials from various different places."
With a case of BSE found in the United States, he added that it is only prudent to re-evaluate the precautionary steps being taken to screen slaughtered cows for the brain-wasting disease that occurs in ruminant, or animals such as cows, sheep and goats, that chew their cud.
The ban on feeding ground up cattle parts to other cattle for protein is believed to help stave off the outbreak of the disease in the United States.
Sundlof said research has shown that as little as half a gram of infected brain fed to cattle, especially calves, can result in the disease in those animals.
"Half a gram is a very small amount, so that if it were to get into the cattle feed there is potential for that even very small dose to result in the disease," said Sundlof.
He added that although it only requires a very small amount of raw central nervous system tissue to infect cows, the tissues are sent through a rendering process.
"This reduces the infectivity by a factor of at least 10, so it would take 10 times that much," said Sundlof.
Sundlof said that cattle are more susceptible to the disease than humans.
"We don't know what the dose obviously is in humans, but it would be much greater than the dose in cattle," said Sundlof.
. Melissa Browning can be contacted at (509) 837-4500, or e-mail firstname.lastname@example.org