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From: TSS ()
Date: June 13, 2006 at 8:34 am PST

In Reply to: USDA, SPONTANEOUS MAD COW DISEASE, THE TOOTH FAIRY AND SANTA CLAUSE posted by TSS on June 12, 2006 at 5:18 am:

BEEF NEWS Two U.S. BSE cases: New questions, no answers by Pete Hisey on 6/13/2006 for

The two cases of bovine spongiform encephalopathy discovered in the United States in the past year or so, one in Texas and the other more recently in Alabama, are distinct from the earlier case discovered in Washington state and from very similar cases discovered in Canada and the United Kingdom, as well as several other countries around the world.

These so-called atypical cases match results in seven cases discovered in France, says Dr. Jean-Philippe Deslys, project coordinator for NeuroPrion, the European Network of Excellence, but are dissimilar to three other French cases as well as a handful in Italy and Germany, among others. The U.S. cases are so-called "high-weight" on a molecular basis, while the other atypical cases are "low-weight." (Results of ongoing experiments on this topic are due to be presented at Prion2006 in Turin, Italy in October.)

What it means is anyone's guess. Deslys says it could mean one of three things: that the "classic" BSE infection has mutated, much like a virus; that these cases are linked to scrapie in sheep or are truly spontaneous like most CJD (Creutzfeldt-Jakob disease) cases in humans and present little or no infective risk; or most ominously, that a new pattern of infectivity has emerged and may not be identified for years.

Deslys points to the spread of chronic wasting disease (CWD), which has moved geographically from the western United States to the Midwest and from there into Canada and the Northeast. Along the way, it has jumped from elk and mule deer to white-tailed deer and perhaps to other species, creating a geographic spread that Deslys says is "now almost out of control. Theoretically, it could be a bovine disease previously unidentified that could spread through feed as BSE does, or by means yet to be identified.

Some scientists believe that CWD may be transmitted through urine, which would indicate a level of infectivity never seen with BSE.

Ed Curlott, a spokesman for USDA's Animal and Plant Health Inspection Service, agrees that the major issue is the source of infectivity. "We have no data on transmission at all," he says. "Right now, we are just following the science."

That may take several years, says Deslys, one of the world's top researchers in prion diseases. In the meantime, he recommends, steps should be taken to increase testing of animals sent to slaughter, and feed bans and other means of controlling amplification of the disease should be maintained or strengthened. "Risk assessment of this development is going to take at least a few years," he says. He notes that, to date, all atypical cases have been found in relatively older cattle, most more than six years of age.

Rapid tests, he says, are getting more sensitive and far more affordable, and coupled with an SRM strategy that keeps the most infective animal parts out of all food supplies, could provide enough protection to keep the disease at bay while research continues.

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