Beverley Mitchell

How We Harvest Horseshoe Crab Blood to Save Human Lives

by , 07/27/14
filed under: Animals, News

Do you give much thought to horseshoe crabs? No, me neither. But it turns out that without them, we could be in a very precarious position. Horseshoe crabs – or to be more precise, their incredible, baby blue blood – are used to test for bacterial contamination, thus saving countless lives each year during medical procedures. The only trouble is, we have to catch a quarter of a million horseshoe crabs each year to do this, and then we have to drain their blood.



Horseshoe crab blood is unusual for two reasons. Firstly, it gets its incredible blue color from the copper used to carry oxygen around the crab’s body, in the same way the iron in hemoglobin makes our blood red. Secondly, horseshoe crab blood reacts to the presence of bacterial endotoxins, coagulating around the contamination and trapping it in a gel-like substance. The blood is so sensitive that it will react to a contaminant concentration of one part per trillion. The chemical component of the blood that causes this reaction, coagulan, is isolated from crab blood to be used in what is known as Limulus amebocyte lysate testing or LAL. LAL tests are performed on medical equipment, vaccines and other injectables: if they don’t cause a coagulation reaction, they’re clean.

Related: The Future of Medicine May Lie in the Fur of the Sloth

In order to obtain horseshoe crab blood, around 250,000 live crabs are harvested along the east coast of the U.S. each year. They are transported to one of five companies, cleaned and then set up in racks for around 30 percent of their blood to be drawn. They are returned to the sea a few days after being caught and are returned quite a distance from the harvesting sites to ensure the same crabs aren’t bled repeatedly. It’s estimated that between 10 and 30 percent of the crabs die during or after the process. One study has also shown that the process is so taxing that female crabs travel less frequently to spawning grounds after being bled, thereby slowing down the rate of reproduction.

One quart of the crab blood extract used for LAL testing costs $15,000. The entire industry is worth $50 million annually. Until the use of of LAL tests was approved by the FDA in 1970, tests for bacterial infection were performed on rabbits. Not only were huge numbers of rabbits required for this process, but their fever reaction that indicates bacterial contamination takes around 48 hours to present. The LAL test takes around 45 minutes. Scientists are currently working on synthetic versions of the coagulant, with one product, PryoGene, already on the market. While this may be good for the horseshoe crabs in the short term, since the previous ways we’ve found to exploit them include using them as fertilizer and whelk bait, they may only be given a brief respite.

Via The Atlantic

Photos by PBS, and Chosovi via Wikimedia Commons

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10 Comments

  1. EthanAndAnna August 15, 2014 at 1:37 pm

    This is horrible. I can’t believe we can’t find another way. Instead of murdering all these animals. What are they going to do when all the animals are gone?

    I never eat these creatures and we all know the population of everything except humans is diminishing exponentially.

  2. rhodesmj August 13, 2014 at 2:09 pm

    think of all the crabs that are caught for human consumption. No complaints there. The loss of a fraction of the horseshoe crab population for the health benefit of humans is unfortunate but obviously necessary for now.

  3. ez August 11, 2014 at 1:11 am

    This really doesn’t make sense to me. When they make vaccines wouldn’t they use sterile ingredients?
    When using medical equipment wouldn’t they just autoclave(sterilise ) it?
    The whole reason they give for the use of using the LAL test just doesn’t add up to me. It just doesn’t make sense????????????????????????????????????????????????????????????????????????????????????????????????

  4. camelot August 9, 2014 at 4:00 am

    The horseshoe crab is a living fossil and it would be terrible if they died out just because they couldnt find another way to do these tests!

  5. meadmaid August 7, 2014 at 4:19 pm

    This is totally disgusting! Draining 30% of a sea creature’s blood by hanging them in the air strapped over bottles? I’ll bet way more than the stated 25% of them die from this “procedure”. So called smart humans can’t do better than this? The horrific things we humans do to animals on this planet makes me ashamed to be called human!

  6. ez August 5, 2014 at 11:50 pm

    Luckily for the crabs the torture won\\\’t go on for much longer as the radiation from Fukushima will either kill them or ruin the blood so it does\\\’t work in for testing and they get left in peace. O and let me guess, it is a Pharmacutical company that abuses these helpless creatures? And the old FDA which is run by the MILITARY that approves it! Of course it is, how convenient!

  7. Ez August 5, 2014 at 11:48 pm

    Luckily for the crabs the torture won\’t go on for much longer as the radiation from Fukushima will either kill them or ruin the blood so it does\’t work in for testing and they get left in peace. O and let me guess, it is a Pharmacutical company that abuses these helpless creatures? And the old FDA which is run by the MILITARY that approves it! Of course it is, how convenient!

  8. dontrue July 27, 2014 at 1:53 pm

    I’m sure there are other ways to check for bacteria other than horseshoe crab blood, enough of the lazy and unnecessary exploitation of animals.

    This is unnecessary use and/or find an alternative.

  9. heather downie July 27, 2014 at 10:47 am

    I,m sick of animals being exploited so relentlessly e.g. hermit crabs, crabs, mares for hormone replacement therapy when they make the mares pregnant every year and murder their foals – no freedom no space. Things could be handled better do you not think? There are synthetic hormones – this exploitation is unnecessary.

  10. Sridhar Pulluri July 25, 2014 at 1:04 am

    One more horrible thing human beings do.

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