Why British People Can't Donate Blood in America

On December 22, 1984, a cow on a farm in Sussex County, England, began displaying head tremors and a loss of coordination. It died a few months later, on February 11, 1985, while other cows began showing similar symptoms. It wasn’t until September of that year that a government pathologist determined that the cow had died from spongiform encephalopathy, later known as bovine spongiform encephalopathy (BSE) or more commonly, mad cow disease. It took several more years for scientists on the Spongiform Encephalopathy Advisory Committee to announce a possible link between the disease in cows and a similar disease in humans, sparking numerous efforts to curb its spread, including banning British beef exports and culling more than four million cows.

While early predictions estimated that the outbreak would kill thousands to tens of thousands of people, there have only been 231 human fatalities worldwide, the majority within the UK. However, in 2013, a study published found that one in every 2,000 people in the UK is carrying the abnormal protein that causes the disease but are not showing any symptoms—at least not yet. An estimated 31,000 people are still carriers of the disease. Preventative measures like blood donation bans are still in place to avoid transmission. In the U.S., if you spent more than three months in the UK from 1980 to 1996, you cannot donate blood. However, as blood shortages continue, hospitals are struggling to have enough on hand.

When BSE is transmitted to humans, it is called variant Creutzfeldt-Jakob disease (vCJD). This is just one of four major types of CJD, which are classified by how they are contracted. In addition to variant CJD, there is sporadic CJD, the cause of which is still unknown; familial or inherited CJD, which occurs when someone inherits an abnormal protein gene from a parent; and iatrogenic CJD, which occurs accidentally in a medical setting. One famous occurrence took place between 1958 and 1985 when thousands of children were injected with human growth hormone collected from deceased donors who were unknowingly infected with CJD.

CJD is an extremely rare but fatal condition caused by an abnormal infectious protein in the brain called a prion. Prions are misfolded proteins that can transmit their misfolded shape onto normal variants of the same protein, inducing them to change their conformation as well. This creates a chain reaction that propagates the disease and generates new infectious material. Before prions were discovered, it was believed that all pathogens, like bacteria or viruses, had to contain nucleic acids to enable reproduction, like DNA or RNA. The discovery of prions opened our eyes to a new mechanism of disease, which is particularly devastating. Their misfolded shape creates brain damage that quickly worsens over time.

Proteins are crucial to our body’s chemistry and are responsible for the structure, function, and regulation of our tissues and organs. They are large molecules made up of hundreds to thousands of organic compounds called amino acids, which are attached in long chains. These chains then fold into a 3D shape, which is key for each protein to perform its specific function. If a mistake occurs, proteins can misfold or fold incorrectly, leading to the formation of abnormal prions. Many diseases are caused by misfolded proteins, leading to a loss of function or causing clumps that disrupt cell function.

Prions also create holes in the brain as they build up, causing brain cells to die and releasing more prions. This results in a sponge-like brain damage that causes symptoms similar to other neurological disorders, like dementia. In variant CJD, psychological symptoms affecting behavior and personality typically develop first, followed by neurological symptoms such as coordination problems, slurred speech, numbness, dizziness, and vision problems. Over time, symptoms worsen until the patient is bedridden, completely unaware of their surroundings, and unable to communicate. The disease always progresses to death.

It took years of research to determine how BSE spread from cow to cow and from cow to humans. Eventually, they identified the source as the cows’ food. At the time, cows were often fed the remains of other cows, so if they ate infected meat, they too became infected. This led to a peak infection rate in 1993 of 0.3 percent of the UK national herd. The government banned the feeding of meat and bone meal to farm animals. Likewise, humans who ate beef containing infected nerve tissue contracted vCJD. Initially, it was thought that humans weren’t affected by the disease, but once it was made clear that they were, bans were quickly placed on British beef exports, and cattle over a certain age were banned from the food chain.

Eating infected beef isn’t the only way humans can contract vCJD, which is where the blood bans come in. There were four cases in the UK where a patient contracted vCJD after receiving a blood transfusion. Quickly, blood donation bans were put in place in countries like the U.S., Canada, and Australia, where people who spent several months in the UK in the 80s and 90s are not allowed to donate blood. This seems like a broad stroke to ban millions of potential donors from just four instances of blood transmission, but it has been necessary because it’s difficult to know for sure if someone has vCJD. There is no blood test that can simply tell you if you have it; typically, a diagnosis is made by considering the patient’s symptoms and through neurological tests like an MRI, which could show abnormalities typical of vCJD. However, even then, it’s not conclusive. The only way to confirm a diagnosis is by analyzing the patient’s brain tissue, which can only be done after death.

Scientists are working on developing a way to test for vCJD in living patients. If successful, the ban could theoretically be lifted. Prion proteins are primarily found in the brain, making them hard to detect in blood. Researchers have developed a method to amplify prions in blood samples called protein misfolding cyclic amplification (PMCA). This method takes advantage of the infectious prions’ natural tendency to convert normal proteins into an abnormal state by combining healthy proteins with a small amount of infectious prions and agitating the mixture with sound waves. Studies have shown that this method can accurately detect vCJD in human blood samples and distinguish it from other types of neurological disorders, including sporadic CJD.

In a 2016 study, it was found to correctly identify those with or without the disease 100% of the time. It can even detect it in patients who aren’t showing any symptoms. In another study published in 2016, tests detected vCJD prions in two patients 1.3 and 2.6 years before they began showing any signs of the disease. While these results are promising, a clinically available blood test has yet to be released. Nevertheless, some scientists believe it’s time to rethink the bans on blood donations, especially with the implementation of safety measures like leukoreduction, which removes white blood cells from blood, as these cells sometimes carry pathogens.

Increasing the number of potential donors is a priority due to blood shortages caused by the COVID-19 pandemic. Since the pandemic began, there have been alarming shortages of blood supplies. For one American blood center, 31 of their locations have a one-day supply or less. Fortunately, changes have begun. In 2019, the Irish Blood Transfusion Service lifted their ban, enabling around 10,000 individuals to donate blood. In 2020, the FDA lifted their ban on U.S. military veterans who served in Europe, now allowing 4.4 million more people to donate. With more testing and trials underway, these broad bans should be lifted in the U.S., saving hundreds of thousands of lives with much-needed blood.

How we treat our farm animals invariably affects our own lives. Diseases like mad cow disease, swine flu, and avian flu spread to us from livestock, often due to poor and overcrowded conditions in which we keep these animals. Keeping the animals healthy will, in turn, keep us healthy. Ending the practice of feeding cows to other cows was a solid step in the right direction, but there are still many other harmful practices, like overusing antibiotics, that need to come to an end. New technologies are being rolled out around the world to help with this, such as automated milking systems that allow cows to decide when they want to be milked, reducing the need for antibiotics.

To learn more about these advancements, you can watch “Milking Robots for Healthier Cows” on Curiosity Stream, part of the European Inventor Awards series. Curiosity Stream is a streaming platform with thousands of high-quality documentaries, and they have partnered with us to offer an incredible deal. By signing up for Curiosity Stream, you also get a subscription to Nebula, a platform made by educational content creators where we can upload our videos and podcasts ad-free. Our newest project is a podcast called “Modulus,” where we talk to the people behind the science we explore on YouTube.

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