Mad Cow disease, or Bovine Spongiform Encephalopathy (BSE), is a disease of cattle thought to be caused by a relatively newly-recognized infectious agent, called a prion - a mysterious proteinlike particle, of uncertain origin. An epidemic of BSE in Great Britain in the late 1990s occurred at about the same time that a new prion-associated disease in humans - variant Creutzfeldt-Jakob disease (vCJD) - was also identified in several British patients. vCJD is a severe neurological disease that appears to be invariably fatal.
So the appearance of two prion-associated neurological diseases - one in cattle and one in folks - led to a hypothesis. That hypothesis was that eating beef from cattle with BSE - that is, ingesting prions from infected cattle - was the cause of vCJD in humans. And despite the persistent lack of proof either that prions actually cause (instead of merely being a byproduct of) vCJD, or that eating tainted beef actually is the cause of vCJD, this remains the accepted hypothesis to this day.
vCJD is indeed a vary scary prospect, and the notion that it was caused by beef fit nicely into the agendas of several well-connected interest groups. (You know who you are.) So, despite the fact that vCJD appears to be exceedingly rare, while eating beef is very common, the worldwide media alerted all people everywhere to the danger. And "mad cow disease" (the media's shorthand for the postulated transmissibility of BSE to humans via beef) became a very big news story for a very long time.
And when cattle sick with BSE were identified in North America in 2003, the general panic reasserted itself. Thousands of tainted cattle, we were told, had likely made their way into the food chain. We had already (probably) eaten it! The ingested prions were even now coursing through our systems (if they actually do that), looking for a likely brain cell in which to take up residence and begin producing sponge! Vegetarians smirked. (They were to get theirs later, when e-coli-and-salmonella-laden fruits and vegetables began sickening scores.) Beef consumption plummeted, and the net worth of McDonalds fell by over $1 billion.
Then suddenly, the story went away.
What the heck happened? Did mad cow disease and vCJD just disappear? Or were we all actually infected, but with a variant that produced mad-cow-disease-amnesia?
Actually, the story just sort of ended. New cases of BSE in cattle have dried up. And the massive number of humans who were expected to develop vCJD never materialized (despite the apparently extravagantly tainted food supply).
There are a couple of possible explanations. We appear to have cleaned up BSE in cattle (by slaughtering infected cattle, and more robust monitoring of herds), and perhaps the food supply hadn't become as tainted as we had feared. So maybe that's it. Seems likely.
On the other hand, a few academics have been brave enough to challenge the entire prion-BSE-vCJD hypothesis altogether. George A. Venters, for instance, pointed out in the British Medical Journal that it is not really clear that vCJD is a new disease after all, or that the BSE prion is infectious to humans, or that prions can be cooked without being denatured, or that they can be ingested and survive the human digestive system or the human immune system. Venters' ideas are decidedly outside the consensus, but then, science does not (or rather, isn't supposed to) function by consensus - and one guy asking difficult questions can rightly challenge the entrenched experts, and, for science to function legitimately, his questions must be addressed.
Whatever the explanation, the actual risk of developing vCJD, even among committed carnivores and even when BSE is around, appears extremely low. So far, only 170 cases of probable vCJD have been identified worldwide, and only three cases have been identified in the U.S., even with all the hype, and all the beef-eating.
Here's more on Mad Cow Disease from About.com's Guide to Rare Diseases.
More of the Top 10 Overblown Health Stories of the Decade.
Sources
Venters, GA. New variant Creutzfeldt-Jakob disease: the epidemic that never was. BMJ Oct 2001; 323: 858 - 861; doi:10.1136/bmj.323.7317.858
National Creutzfeldt-Jakob Disease Surveillance Unit. Edinburgh, Scotland, www.cjd.ed.ac.uk/figures.htm (Accessed December 3, 2009).
