Bovine Spongiform Encephalopathy, often called mad cow disease, made the news most recently when the USDA confirmed its fourth case in a dairy cow in central California. According to the USDA statement "[i]t was never presented for slaughter for human consumption, so at no time presented a risk to the food supply or human health. Additionally, milk does not transmit BSE."
A Closer Look at Mad Cow Disease
Dangerous or not, it left many wondering whether they were ever at risk of contracting mad cow, so I thought it prudent to take a closer look at what the disease actually is and the dangers it presents to both humans and animals.
Bovine Spongiform Encephalopathy (BSE) has a confusing name, but each portion of the name makes good scientific sense. Bovine means cow, spongiform refers to the idea that infected cow brains look like sponges, and encephalopathy means disease of the brain.
It’s a chronic degenerative disease affecting the central nervous system of cattle. It gets worse over time and the body doesn’t know it’s infected so it can’t fight the disease. Symptoms in cattle include incoordination, trouble walking and getting up, anxiety, and violent behavior.
Cows can have the disease for four to six years before even showing symptoms and they usually die two weeks to six months after the symptoms occur. There is no treatment, no vaccine, and no reliable way to test for it. Although after the cow has died, you can tell by looking at the brain.
How Cows Get Mad Cow Disease
Cows get mad cow disease from eating feed that’s contaminated with diseased cattle. You heard it right. Some cow parts or reused in the feed that they then eat. It’s like cannibalism but for cows. It’s usually eaten in feed during their first year of life though cows aren’t diagnosed with it until years later. In April 2009, the FDA banned “high risk” cow parts, including brains and spinal cords, from being used in feed as a safety precaution.
The first infections were recorded in 1986 in two cattle in the United Kingdom and infections peaked in 1993 when 1,000 cases were recorded each month in the UK. As of February 2011, 22 cases were found in North America, 3 in the U.S., and 19 in Canada.
Mad Cow in Humans
The human form of the disease is called variant Creutzfeldt-Jakob disease not to be confused with the non-variant form of Creutzfeldt-Jakob disease. Researchers think humans get it from eating cows contaminated with mad cow though you can’t get it from drinking milk. Four cases of the disease have also come from blood transfusions though patients didn’t show symptoms until years after getting the transfusions.
Human symptoms are first characterized by depression, anxiety, and painful senses. Later, victims experience difficulty walking, involuntary movements and when they are upon death, they may go mute and become immobile. In 2011, there were only 29 cases worldwide.
There have been no cases of mad cow disease from cattle raised in the U.S. and the federal government has thus far been very successful at keeping it out of the food supply. The USDA tests about 40,000 cows a year out of the 34 million slaughtered. Though undoubtedly a nasty disease with a scary name, it's very rare especially when compared with salmonella and e coli.