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73. The Crab and the Vampire

03 Apr

Horseshoe Crabs, odd little creatures indeed. They wander around in shallow ocean waters, surrounded by clouds of dirt and silt. It has been around for over 250 million years. Now it has something new to worry about… vampires.

The Horseshoe Crab has blue blood; and we want it. We are their vampires.

So why? What on earth has possessed us to make us want to harvest the precious blue blood of this harmless relic from many years past. The simple answer is to sustain us. Simply, their blue blood is a bona fide medical marvel.

In 1971 some scientists decided to introduce E. coli bacteria to some of the blood. The blood reacted, it clotted and stuck around the bacteria, preventing further spread. This was great news for the scientists, it showed a reaction to endotoxins produce by many types of bacteria that can cause humans to get fevers or haemorrhagic strokes.

Filled with delicious blood!

The simple clotting mechanism was very useful indeed. For the crabs it is their whole immune system, living in an environment where there can be billions of bacteria per millilitre they hang under the constant threat of infection, and the clotting mechanism is their way of fighting it. The secret is a compound in the blood called LAL (Limulus Amebocyte Lysate) which performs all of the clotting action, neutralising threats from fungi, viruses and bacterial endotoxins.

That is good for the crab and good for us. The clotting happens in under an hour and Horseshoe crabs were plentiful, as well as easy to catch. The Biomedical industry saw its opportunity and once the FDA approved the blood clotting test the blood frenzy began. These days the crab-blood test is the worldwide standard screening for bacterial contamination. A worldwide standard requires resources.

A $50,000,000 industry sprung up, harvesting the crabs along American coasts and selling them. How many? 250,000 crabs a year. Each of which are carted off to LAL laboratories wherein they are washed and examined for any signs of ill health or wounds, we are conscientious vampires after all. If they pass muster we then get about the blood business, draining each crab of up to one third of their blood with a large gauge needle. The blood is then carefully bottled and sent around the world at a handsome profit. One quart (just under a litre) of the blood fetches $15,000, such is our desire for it.

Now, we are not vampires in reality. We don’t really want the blood, just the LAL inside it, and unfortunately the only way to get that compound is to get that precious blood. You see, we need it for just about everything medical. For any drug to be approved, it has to pass trial by blue blood. Any surgical implant such as a pacemaker or prosthetic limb, trial by blue blood and so on. There is a demand and it puts strain on the species.

After harvesting the crabs are placed back in the ocean and take several months to recuperate and build up their blood levels, unfortunately they can go through it all again. The excessive trawling means that it is possible for crabs to be harvested up to four times a ear, an amount that can certainly result in some sick crabs.

The practice of draining their blood is not so safe either, recent surveys suggest that between 20,000 and 38,000 crabs die after bleeding. That’s a death rate of 10 – 15%. Populations then dropped in size and now we are finally taking steps to protect these creatures. Regulations have been put into place so as to prevent over-harvesting. These are all steps in the right direction, however an alternative may be needed. Scientists are working hard to try and produce LAL on its own in the lab, or at least find another source. Until then, humanity shall be medicinal vampires.

Think on that for moment the next time you have any pill or medicine. Think ‘I am a crab vampire’. Even if it makes no sense, at least it’s an interesting thought.

Further reading : detailed article

 
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Posted by on April 3, 2011 in Articles, Trivia

 

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