Imagine a field with millions of cows casually grazing. Imagine them all suddenly dead. Bovine Spongiform Encephalopathy, more commonly known as Mad Cow disease, or BSE, has killed over 4.4 million cows. BSE is a temperate disease, meaning it stays inside of the cow for years, before it finally attacks. Mad Cow disease isn’t like other diseases, as it isn’t caused by a virus or bacteria, but by a protein called a prion.
A prion is a misfolded protein, they are the cause of multiple fatal neurological diseases called TSEs or Transmissible Spongiform Encephalopathies including BSE in cattle, Chronic Wasting Disease (CWD) in deer, Scrapie in sheep, Feline Spongiform Encephalopathy (FSE) in cats and Variant Creutzfeldt-Jakob disease (vCJD) in humans. All of the TSEs are fatal. Because scientists don’t know how the proteins fold into prions it is nearly impossible to find a cure. Though there is a medicine that will slow the symptoms.
The prions journey begins inside of the body of a dead cow. Often the parts of a cow that are not eaten get ground up and used as an ingredient in animal feed, this is what happens to that dead cow, and the prion. A one-year-old cow will then eat some of this contaminated food. The prion enters the cows body. Inside of the cows system the prion works its way to the central nervous system (the brain and spinal cord), there it clumps in brain and waits. In about five years the cow will start to show symptoms of BSE. They may show aggression or nervousness. They may have abnormal posture, bad coordination, difficulty rising and decreased milk production. Once a cow shows the symptoms, they will die in two weeks or up to six months.
Essentially, prions are like little ninjas, slipping into a cows body, killing it and moving into new cow, repeating the process. Because the disease is a temperate disease, the cows body has no way of knowing that they may die. Prions are extremely resistant to things like heat, ultraviolet rays, ionizing radiation, usual sterilization processes, and disinfectants that are usually used for viruses and bacteria (no surprise there). Prions are even able to go through a cell’s cytoplasm unnoticed and evelove specifically for each host.
One thing that is interesting about prions and the immune system is that the immune system does not attack the prion. This is because prions are misfolded proteins, so the immune system doesn’t see anything wrong, just a protein. This makes the immune system not attack and send B-cells out of the bone marrow or T-cells out of the thymus glands to stop it. Thus, the prion is able to head to the cows central nervous system.
If the immune system were to notice the prion it would probably go to its third option: Immune response. During immune response the helper T-cells sends a chemical alarm through the body to the B-cells to get them to attack the disease. B-cells are able to produce antibodies that chemically invade the disease. If the disease dies T-cells stop the attack while memory T and B cells stay in the bloodstream. If the disease is still alive the attack goes on until either the infected or the infector dies. It was in 1986 when the first case of Mad Cow disease was discovered in the United Kingdom. After that there were BSE cases left and right, killing 180,000 cattle in just 15 years. Thats 12,000 cows dead per year and about 32 deaths each day. In January 1993, the epidemic in Britain reached its peak, with almost 1,000 cases being reported each week this had previously been about 230. Three years later the first case of vCJD was reported. The European Union then decided to ban British beef, the French decided to continue this ban for another three years.
On May 20, 2003, Canada found its first case of BSE in an eight-year-old cow. A day later multiple countries decide to temporarily ban Canadian beef. That December the USDA (United States Department of Agriculture) conforms the first US case of Bovine Spongiform Encephalopathy in a Washington cow that had been born and imported from Canada four months before the US banned Canadian beef. Around this same time Japan, South Korea, and China all banned US beef. On January 9, 2004, the USDA say that they will be killing the 130 other herd-mates of the cow that tested positive of BSE. Later, on the 26, safeguards were put up by the Food and Drug Administration that banned chicken waste from cattle feeding and restaurant scraps from being used in animal feed. On June 20, 2004, Charlene Singh, the first person to live in the United States with vJCD dies. On January 2, 2005, Canadian officials conform a case of BSE in a 10-year-old cow. On June 24 and March 13, two more cases in the US were found.
Then on September 5, 2008, Canadian scientists announce a discovery that paves the way for diagnostic testing of live cows, rather than postmortem. Eight days later, an Alabama research study shows that BSE can sometimes be caused by genetic mutations. On March 14, 2009 US government permanently bans the slaughter of cows to sick or weak to stand on their own, to minimize the contraction of mad cow disease.
On April 24, 2012 the USDA conformed a fourth case of BSE in a dairy cow. Then, after fifteen years, the US finally decided to lift the ban on beef off of the European Union. In 2016, France conformed the first case of BSE since 2011. More recently, on October 18, 2018, Scotland confirmed an isolated case of BSE on a farm in Aberdeen. With the fact that cases of BSE have been dying down, I don’t think that there will be another empedemic like the one in 1986. Maybe scientists will find a cure for any or all TSE diseases or maybe they will find what causes proteins to misfold. Both of these will create a more hopeful future for neurological diseases and cows.
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