More On The Mad Cow Case

Mother Jones gives a little more detail on the recent BSE case (h/t nc links):

The California cow's BSE might have come from feed—and cows are still being fed cow protein. Now, as noted above, the USDA reports that the California case had "atypical" BSE, which, it says, is thought to derive spontaneously, not from feed. "USDA confirmed the animal was positive for atypical BSE, a very rare form of the disease not generally associated with an animal consuming infected feed," the USDA wrote in a Wednesday statement. In a Friday morning email, a USDA press officer confirmed to me that the atypical BSE in question is of the L-type, which, as I showed in my last post, has been shown under lab conditions to be far more virulent than what scientists call "classical" BSE, the kind that wrought havoc in the UK in the 1990s.
The feed question is vital. If the cow indeed developed BSE through some genetic mutation and not through feed, then this particular mad cow instance can be viewed as a random and extremely rare event. But if feed was the pathway, then we have to ask hard—and for the dairy and beef industries, extremely uncomfortable—questions about just what we're feeding our nation's vast herd of cows. And if that cow contracted BSE from what it ate, wouldn't other cows have been exposed, too?
Paul Brown, a scientist retired from the National Institute of Neurological Diseases and Stroke, questions the USDA's assertion that atypical BSE isn't associated with feed. "The most likely explanation is that it arises from the same source as typical BSE," he said, which is infected feed. He added that it's a "theoretical possibility" that the California BSE case arose spontaneously, but "there's no evidence for it."
Linda Detwiler, a clinical professor in the Department of Pathobiology and Population Medicine at Mississippi State University, told me via phone that the current scientific thinking is that "atypical" BSE types do probably arise spontaneously, but "feed certainly can't be ruled out." Ermias Belay, associate director for epidemiological science at the CDC's  Division of High-Consequence Pathogens and Pathology, echoed that assessment in a phone interview.

The story goes on to discuss feeding chicken litter, which will contain chicken feed which may have rendered cattle protein.  It also mentions that the U.S. screening process for BSE is extremely lax, and that the cow which tested positive in California had been a downer cow from a dairy which had been euthanized before it was dropped off at the rendering plant, and that it was tested as part of the random testing.  Those are both interesting points which the beef industry and government should investigate.  Something tells me they won't look very far into this case.