Lots of interesting reporting this week following up on the discovery of mad cow disease in California. Perhaps the most compelling analysis comes from msnbc.com: Are USDA assurances on mad cow disease ‘gross oversimplification’?

Robert Bazell, NBC News’ chief science and medical correspondent, says that several top scientists say the public health implications may not be as clear the U.S. Department of Agriculture would have us believe. And he explains the concerns quite thoroughly.

Bazell reports that the diseased dairy cow actually was infected with a condition variously known as BASE (bovine amyloidotic spongiform encephalopathy), atypical BSE and L-type BSE, which has so far been found in about 70 animals in the world:

This condition, first reported in two Italian cows in 2004, causes the same rapid crippling and death as the classic bovine spongiform encephalopathy (BSE) that swept through Britain and much of Europe in the 1980s and '90s. But the brains of the animals look very different after their demise.

Some experiments have shown that this rare disease can jump from species to species, infecting lab mice and even non-human primates. The research also suggests that the infectious agent for the rare disease could be more virulent than BSE, more likely to appear in meat (classical BSE is mostly in brain and nervous tissue) and might be carried in milk. Many scientists are quick to point out that all this research consists of studies too small to be conclusive. 

However, there is an urgent need for further study, they say.

What irks many scientists is the USDA’s April 25 statement that the rare disease is “not generally associated with an animal consuming infected feed.”

Bazell asks how could the California cow have been infected with feed?  And if it is feed, what does that say about the potential of an outbreak in the rest of this cow’s herd? There are no definitive answers yet.

Reuters, meanwhile, reports that government data indicate major importers actually stepped up their purchases of U.S. beef last week.

The muted trade reaction suggested importers were comfortable with the safeguards enacted since the discovery of the first U.S. case of mad cow disease in December 2003.

Mexico, South Korea, Japan and Canada, which combined took 65 percent of U.S. beef exports last year, as well as the European Union said they would continue to import U.S. beef. However, two Korean retailers have halted sales, Reuters said.