What Causes Mad Cow Disease?
Mad Cow disease is technically known as Bovine Spongiform Encephalopathy. It belongs to a class of diseases, known as transmissible spongiform encephalopathies. Basically meaning, diseases that leave your brain looking like a wet sponge. Humans are obviously not part of the bovine species, thus, when Mad Cow is transmitted to humans, the diseases name is called variant Creutzfeldt-Jakob disease (vCJD). Creutzfeldt-Jakob (CJD) being one of 4 types of human spongiform diseases, and Mad Cow being the cause of a variant of that. Now that you’re confused from the start, let’s talk about what all of this really means.
Spongiform encephalopathy’s leave the brain riddled with tiny holes, giving it a sponge-like appearance. As you can imagine, your brain filled with holes will leave you with all sorts of symptoms. Things like; personality changes, psychiatric problems, and lack of coordination. As the disease worsens, those symptoms progress in to involuntary jerking movements, confusion, and memory problems progressing to severe mental impairment. The victim then loses the ability to move or speak altogether. Once enough holes are present within the brain, it will cease to work properly and the victim dies. This not-so-rosy outlook for those diagnosed, can owe it all to a type of protein called a prion.
Proteins in the body start out with a primary amino acid sequence. Then they fold into secondary shapes. Normally giving it a structure known as an alpha-helix. This allows them to fulfill whatever function the body needs. When an animal or human is born with a certain type of abnormal gene (condon 129), it causes those proteins to fold into a structure called a beta-sheet, instead of its normal alpha helix. These malformed proteins are known as prions.
Prions clump together into fibers called amyloids. Amyloids bind together on the surface of brain arteries and cells. The result is death to those cells. Prions also have the Borg-like habit of forcing other proteins around them with similar amino acid sequences, to take on their shape (Shameless Star-Trek reference intended).
All of these amyloids spread throughout the infected central nervous system, causing numerous pockets of dead cells that result in the holes in your brain and spinal cord. Alzheimer’s disease is also thought to be a result of the accumulation of Amyloids within the brain. Prions, however, are not the cause in Alzheimer’s case.
Mad Cow disease is only one of numerous diseases throughout the animal kingdom that cause this same problem. There is Scrapie, affecting sheep and goats. Chronic Wasting disease in elk and deer. Human forms of spongiform diseases include; kuru, fatal familial insomnia, Gerstmann-Straussler-Scheinker disease and the aforementioned CJD.
The first cows thought to be infected with Mad Cow were from a Pitsham farm in West Sussex, England. They began showing unusual symptoms in December of 1984. It was their abnormal behavior and loss of ability to do simple things that got them the name “Mad Cow”. Mad being a term for crazy. It wasn’t until 2 years later, in 1986, that the Central Veterinary Laboratory in Weybridge England formally diagnosed the disease as Bovine Spongiform encephalopathy.
In 1996 researchers noticed a new form of CJD and called it vCJD. It was then discovered the prions from vCJD were molecularly similar to the ones in Mad Cow. Scientists then realized this disease could cross the species barrier and paranoia surrounding possible infection spread through the UK, and the world, like a cold in a 1st grade class room.
No one knows for sure where Mad Cow disease came from, but the prevailing theory is that it came from Scrapie, the sheep version of the disease.
Prior to Mad Cows outbreak, it was common to make dietary supplements for cattle from the meat and bones of sheep and other cows. The timing also coincided with changes in the way this protein slurry was processed in the UK. Instead of liquefying the carcasses of sheep and cows into a proteinaceous mix, they instead fed the meat through rendering equipment. It was thought this resulted in uneven heating of the slurry. When the UK banned this practice in 1987, 5 years later there was a marked downturn in the number of new Mad Cow Cases. 5 years being the average intra-species incubation period of Mad Cow.
All told, there have been approximately 184,500 confirmed cases of Mad Cow disease in the UK. Only 4 known cases have ever been confirmed in the United States. The number of infected peaked in 1993 with around 1,000 new cases found each week. Due to the strict regulations set in the processing and handling of cattle, new cases have drastically been reduced to just 11 total cases in all of 2010.
Despite the millions of people who were exposed to beef during the highest points of outbreak, to date, only 153 total people have died from vCJD as a result of eating infected meat, or from blood transfusions from those who were infected. 143 were from England, and 10 were from other countries.
While Creutzfeldt-Jakob disease affects approximately 1 in every 1 million people, the variant form that comes from Mad Cow is even rarer. With the total number of Mad Cow cases becoming increasingly scarce, it’s sure to follow that vCJD will also become a problem of the past.
So eat your beef secure in the knowledge it didn’t come from mad cows. Although, I’m sure they were still a bit upset about being eaten, despite their happy demeanor.