November 07, 2004

How now mad cow?

Let's talk about something other than the election, something more optimistic. Let's talk about mad cow disease.

I wouldn't have thought of mad cow disease, except that in my Legislation course, we were divided up into groups and asked to write a piece of legislation that would protect America from the scourge of bovine spongiform encephalopathy. The story behind this public health menace is fascinating.

Many mammals, including humans, cows and sheep, suffer from degenerative neurological diseases--the "transmissible spongiform encephalopathies" or TSEs-- caused by what many people now think is an abnormal protein--a prion. In sheep, the disease is called scrapie; in cattle it's called mad cow disease. The infectious agent that causes these diseases, probably a prion, is concentrated when an animal eats the carcass of another of its kind, and especially the neural tissue of the brain and spinal cord. Yummy. Cannibals in Papua-New Guinea, for example, are susceptible to a form of TSE called kuru.

These diseases can cross the species barrier. If you're not a cannibal, but you eat certain parts of a cow with mad cow disease, you can get a TSE called Creutzfeldt-Jakob disease. It causes dementia, and it's always fatal. If there's a particularly heavy load of infectious agent in a carcass, it's more likely that the disease will infect whoever eats it.

The problem is, our industrialized agricultural practices involve a lot of things that tends to concentrate the infectious agents of the various TSEs. We feed a whole lot of animal carcasses to other animals: cows to cows, cows to chickens and pigs; zoo animals and roadkill to cows and chickens and pigs, etc. etc. Many animal feeds are made with the products of "rendered" carcasses of dead or diseased animals. The carcasses are tossed in a vat, melted down, and separated into proteinaceous materials, fats, and whatnot. These carcass-products are the main ingredients in livestock feed, pet food, bologna, etc.

After a cow in Washington State was discovered with mad cow disease in 2003, the USDA issued some basic regulations designed to keep the mad cows off our dinner plates: non-ambulatory ("downer") cattle weren't allowed in the slaughterhouses anymore. Certain parts of cattle--brains, spinal cords, terminal ilea--were prohibited from going into bologna and sausages. Having issued these regulations, Agriculture Secretary Ann Veneman spent the rest of her time trying to convince the public that their meat was safe. The National Cattlemen's Beef Association no doubt appreciated the Secretary's efforts.

There remains no ban on feeding the products of animal carcasses, even diseased ones, to livestock animals that enter the human food chain. The rendering plants that melt down these carcasses are not yet required to follow methods designed to eliminate the infectious agent that causes mad cow disease, and they are permitted to accept "downer" animals for processing. There is no national system for tracking individual cows, as there is in many other developed countries. There have been occasional tests of animals sent to slaughterhouses for mad cow disease, but the percentage of animals tested remains extremely low. (This has been one of the reasons Japan has not dropped its ban on American beef just yet.)

Needless to say, there is a lot of room for more legislation on this issue, which made it an excellent exercise for our class. Now, if you'll excuse me, I'm going to go get me a burger. With the USDA on the case, I know it's safe!

Posted by Carey at November 7, 2004 10:38 PM