A fourth case of mad cow disease and still the safest food supply in the world.

As you may already know, a dairy cow in California was diagnosed with Bovine Spongiform Encephalopathy (BSE), commonly known as Mad Cow Disease. The 10 year old cow died at an undisclosed dairy farm, and the disease was found when her body was sent to a rendering facility. Here is the official release from USDA.

Why am I not worried about this?

First, the cow was not destined for our food supply. She was at a rendering facility. These are companies that dispose of dead animals and produce inedible products. There is a testing system set in place by USDA to test the bodies of a certain number of the cows for BSE before they go through their process.

What about the milk she produced? BSE is not transmitted through milk.

I heard on the radio last week that her offspring are going to be euthanized to keep them out of the food supply, too.

What about the rest of the beef supply? BSE is not transmitted through meat, either. However, BSE is found in the nervous system. The USDA has very stringent rules in place to keep BSE out of our food supply.

What are those safeguards?

The molecule that causes BSE is only found in a few places in the body including the nervous system, small intestine, and tonsils. The small intestines and tonsils of all beef cattle are no longer used in the food supply. Also, BSE is much, much more prevalent in older animals. The USDA requires that beef processors look at the teeth of every animal slaughtered to determine how old they are. If they are older than 30 months, then the spinal cord, brain, eyes, and any parts that may contain nervous tissue are also removed from the food supply. They refer to those parts as Specified Risk Materials.

Cows that have BSE have a very hard time walking and eventually get where they can’t move on their own. We refer to those cows that cannot get up on their own as ‘down(ers)’ or non-ambulatory. Down cows are far more likely to have BSE, and when cows are down, veterinarians cannot observe the signs of BSE. Therefore, if a cow is down and cannot get up, then she may not be harvested for human food.

Also, BSE was previously transferred from cow to cow because meat and bone meal from cattle and sheep was fed to other cows as a protein source. The US (FDA) banned that practice in the 1997. So, we shouldn’t be spreading the disease anymore.

Are the safeguards working?

Yep. Like a charm. This was only the 4th case in the US ever and last year there were only 29 cases worldwide. In 1992, there were over 37,000 cases.

Although some people were sickened in Britain in the 1980’s and 1990’s, no one in the US has been known to have been sickened from eating beef from BSE infected cows.

How do cows get BSE?

BSE is an infectious disease that is transferred from animal to animal in a rather unique way. The infectious agent of BSE is a protein called a prion (pronounced pree-on). All animals have prions. Prions, like all proteins, long chains that are folded up in a specific way. In healthy animals, the prions are folded into several helical shapes (kind of like a slinky gone wrong). Scientists call them alpha-helices.

  In animals with BSE, the prions have refolded and the helical shapes have changed to flat, sheet structures, called beta-sheets. These beta-sheets allow the prions to stick together and form plaques. Those plaques cause changes in brain function and make the animal sick.

What is weird about BSE is that, when these bad prions are introduced to the body, the bad prions teach the good prions how to be bad. Somehow, they cause the healthy prions to refold themselves. Maybe we should call them zombie prions.

So, when a bad (zombie) prion is introduced, it takes a while, but it can teach all the healthy prions to refold. How are bad prions introduced?

 1. Well, sometimes the prions just sporadically decide to change. That is really rare. But, when it happens, the animal will slowly form more and more bad prions until it becomes ill.

2. Sometimes it is genetic. The bad prions are passed from parents to offspring.

The dairy cow in California has been found to have atypical BSE, which means she developed BSE in one of the above ways.

3. BSE used to be passed between cows through feed. When animals are slaughtered, not every part can be eaten by humans. Some parts and pieces are converted to a product called meat and bone meal. Farmers used to feed meat and bone meal back to other cows as a source of protein. Bad prions were being spread that way in Britain in the 1980’s and 1990’s. When scientists realized that was happening, this practice was banned. So, the cow should not have gotten BSE that way.

What about other animals?

Cattle are obviously not the only animals that get this type of disease. Humans have similar diseases caused by bad prions known as Creutzfeldt-Jakob disease, Kuru (found in native people in New Guinea who practiced ritualistic canabalism), Gerstmann-Straussler-Scheinker disease, and Fatal Familial Insomnia. The bad prions in humans come from similar sources as cows; including genetic, sporadic, and from food (meat containg nervous tissue from cattle with BSE). Some people have gotten the disease through neurosurgery or eye implants.

Scientists think BSE in cattle may have originated from a disease in sheep called scrapie. Meat and bone meal from sheep fed to cattle contained bad sheep prions.

Deer and elk also get a disease called Chronic Wasting Disease. Big cats and exotic ungalates (antelopes etc.) contracted forms of spongiform encephalopathies during the height of the BSE epidemic in Europe.

The safegaurds in place to protect humans are also protecting these other species.

There are lots of websites with information about BSE.

My friend Ryan Goodman at I am agriculture proud has compiled several sites.

There is a new website called BSEinfo.org. Several of my links will take you there.

If you have any questions or concerns, please feel to comment.