Mad Cow Disease

Mad Cow disease - it conjures up visions of cows on the rampage. But it's not like that. Infected cattle tend to basically waste away. This is the result of their brain tissue degenerating or falling apart. Mad cow disease became news in 2001. But it isn't all that new.

Where it started

Bovine spongiform encephalopathy (BSE), known as mad cow disease, was first identified as a separate disease in 1986. Ground zero was Great Britain. At the peak of the epidemic in 1993, one thousand cases a week were being reported. Some other countries have had outbreaks but most of the cases have been in Great Britain.

The disease has a long incubation period, anywhere from 2 to 8 years. And even though it's a long time from infection to showing signs of the disease, once the signs are there, death comes quickly, 2 weeks to six months later.

What causes BSE

It's not exactly known what causes the disease, but scientists are zeroing in on nervous system tissue and some sort of agent, something smaller than a virus. According to USDA, it appears that BSE was spread by animal feed mixed with the body parts of infected animals. In the past, it was common practice to grind up unused parts of the cattle carcass and mix it with feed to be fed to other cows. Because of the long incubation period, infected animals that didn't show signs of the disease spread it when they were killed and their nervous system tissue was mixed into feed for other cattle.

U.S. action

Until late 2003, U.S. government officials said BSE had never shown up in the United States. However, just before Christmas 2003 USDA announced the first case in the U.S. had been discovered in an animal from a farm in Washington state.

In 1989, the USDA's Animal, Plant and Health Inspection Service (APHIS) banned the importation of cattle from countries where BSE had shown up. It also banned by-products from cattle such as bonemeal, blood meal and glands. Feed, that contained any cattle by-products, was also banned. The ban was extended in 1997 to include all the countries in Europe.

Human impact

March of 1996 saw a major announcement from researchers in the United Kingdom. It looked like BSE was showing up in humans as a new variant form of Creutzfeldt - Jakob Disease (vCJD). (Read about "Creutzfeldt-Jakob Disease") The new disease, vCJD, is a brain degenerative disease (Read about "The Brain") with a long incubation period and it is always fatal. It's believed that the disease was passed to humans by the consumption of cattle brains or other nervous system tissue in some way. The exact means has not been identified.

Continuing concerns

The USDA, the CDC and the Food and Drug Administration continue to run monitoring programs to keep potentially infected material out of the United States.

Outside the U.S., CDC officials say there is no way to measure precisely the risk of contracting vCJD from eating beef products in Europe. They estimate however that the chance of getting vCJD from beef is perhaps one in 10 billion servings of beef even in the United Kingdom. To reduce any risk, the CDC says travelers to Europe should consider the following:

• avoiding beef and beef products altogether
• selecting solid cuts of beef instead of burgers or sausage

Milk and other milk products from cows are considered safe, according to CDC, and are not believed to pose any risk of passing on the BSE agent.

The future

Because of the long incubation period before vCJD shows itself, health and agricultural officials on both sides of the Atlantic remain concerned. One of the first ten people who died from the disease had been a vegetarian for at least 5 years before they died. That means people may be infected today but won't show signs for months or years.

Related Information:

    Blood Donation Guidelines

    Microorganisms

    Food Safety