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Reluctant donors: why do pharmacists need horseshoe crabs blue blood and how will it help the COVID-19 vaccine?

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They have ten eyes, they reach 60 centimeters in length, live on Earth for more than 300 million years, and they really have pale blue blood, which is highly valued in pharmacology and saves our health.

Photo: ru.wikipedia.org

No, this is not science fiction, but ordinary, good old science. Meet: horseshoe crabs, or, as they are also called, horseshoe crabs - although, strictly speaking, they, in fact, are not crabs, but their closest relatives are arachnids.

People are very dependent on horseshoe crabs, or rather, on their blood, which, among other things, is used to determine the purity of medicines, and now also to create a potential vaccine against coronavirus.

However, each medal has a flip side, in this case it is the life of the horseshoe crabs themselves, who also need their blood (in fact, hemolymph, in fact, is a cross between blood and lymph).

Therefore, conservationists want to end the practice of milking these crabs (let's call them that for convenience).

What are the benefits of horseshoe crabs?

The blood of these "living fossils" has a unique property: it coagulates when even the smallest amount of pathogenic bacteria or other foreign microorganisms gets into it, turning into jelly. Thus, the immune system of horseshoe crabs protects other organs from damage.

By checking new medicines using an extract made from the cells of this hemolymph, scientists can be absolutely sure that they have not gotten bacteria or their waste products, which can then harm a person.

Only the blood of horseshoe crabs has a similar amazing property.

Therefore, every year thousands of these crabs are caught in the sea and sent to American laboratories, where some blood is taken from them, and then released.

The reagent extracted from the hemolymph of horseshoe crabs is highly valued - the cost of one liter Limulus amebocyte lysate is about 15 thousand dollars, which makes it one of the most expensive medicines in the world.

What then happens to the "donors"

Every year, more than half a million of these animals are caught for the needs of pharmaceuticals.

At first, experts believed that almost all horseshoe crabs safely survive such forced donation. Another ability of these sea creatures is that they donate exactly as much blood as they can donate without harming their health.

However, according to recent estimates, as a result of this procedure, up to 30% of individuals die.

Other studies have shown that female crabs are less likely to mate after blood is drawn.

And all this in aggregate, according to animal rights activists, creates serious problems for these arthropods.

“Right now, they are milking about half a million crabs,” laments Dr. Barbara Brammer, who leads a group of environmentalists in New Jersey, where most of the American horseshoe crabs are caught.

In an interview with the BBC, she complained that no one knows for sure how blood sampling affects the future life of crabs after they are released.

As a result, American horseshoe crabs have approached the threshold beyond which they can be officially considered endangered.

At the same time, large pharmaceutical companies point to statistics according to which the number of horseshoe crabs has remained unchanged over the past years.

Can't you find an artificial substitute?

Research aimed at creating an artificial analogue of the extract from the hemolymph of the horseshoe crab has been carried out for a long time, but the real breakthrough occurred only in 2016.

Scientists managed to create a substitute that was approved for use in Europe. Some American pharmaceutical companies have also started using it.

It would seem, what is the problem then?

And the fact is that in June of this year, the organization responsible for drug safety in the United States (the Food and Drug Administration, or FDA), said that it could not guarantee that the substitute worked as reliably as natural product.

Therefore, all companies that want to sell their drugs in the United States are required to use horseshoe crabs to test them for purity.

The same applies to any potential coronavirus vaccine: whoever invented it will be obliged to test it in the old proven way if he wants to sell his product to millions of Americans.

Dr. Brammer wants to force the American authorities to reconsider their approach, especially since in other countries an artificial substitute is already being used everywhere.

“We need to stop depending on this natural source,” she says.

Some pharmaceutical companies say they can meet the need for a coronavirus vaccine without increasing their crab catch.

However, according to Barbara, at least 30 companies are working on the vaccine, and each of them will be required to test.

“So I am very concerned about the size of the horseshoe crabs population,” says Dr. Brammer. "After all, they are the key link in the ecosystem."

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