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article imageHorseshoe crab blood is saving lives - now we need to save them

By Karen Graham     Dec 30, 2014 in Science
Horseshoe crabs have been around for over 450 million years, which is astounding enough, and they have also survived three great extinction events. But the most astounding thing about them is their blood. It is a bright baby-blue.
While not actually a crab, but like a "true" crab, they are members of the Arthropod family. They are thought to be the most primitive living examples of arachnids, like spiders, mites, and scorpions. But it's the blood of the horseshoe crab (Limulus polyphemus) that is so miraculous. The blue blood of this creature will coagulate and surround any bacteria, walling-off the invader and essentially healing the wound.
During WWII, while medical care had come a long way since the early 1900s, soldiers still had a fear of being treated on the battlefield or in field hospitals. Medical equipment, intravenous solutions, and supplies were often breeding grounds for pathogens, particularly Gram-negative bacteria, and wound infections were quite dangerous.
The horseshoe crab is truly a living relic from our past. They have been on earth for around 450 mil...
The horseshoe crab is truly a living relic from our past. They have been on earth for around 450 million years.
Today, with the advent of better medical hygiene and procedures, the chance of getting a severe infection while on a treatment table has been greatly reduced. Our safety, while receiving treatment, whether it's surgery, complicated procedures or getting intravenous medications is because of an unlikely source, the baby-blue blood of the horseshoe crab.
Limulus Amebocyte Lysate walls off "bad germs"
Horseshoe crab blood does not contain hemoglobin, the stuff that transports oxygen, like human blood. Instead, the horseshoe crab uses copper-containing hemocyanin to transport oxygen, and this is why its blood is blue. It wasn't until 1956 that Dr. Frederik Bang, a medical researcher at Johns Hopkins University, discovered that massive clotting occurred when a common marine pathogen was injected into the bloodstream of the horseshoe crab.
Screen grab from the PBS documentary   Crash: A Tale of Two Species   showing the harvesting of the ...
Screen grab from the PBS documentary " Crash: A Tale of Two Species," showing the harvesting of the blood from horseshoe crabs.
Further research uncovered a most unusual compound in the horseshoe crab's blood, called Limulus Amebocyte Lysate or LAL. Instead of an immune system, the LAL attacks infections, clotting around the germs, such as bacterial endotoxins, viruses, and fungi. The blood actually turns into a jelly-like glob, effectively isolating the pathogens. It was because of this unique component of the horseshoe crab's blood that the LAL was used to set up an international standard screening test for pathogens and toxins in the biomedical field.
Nature's method is now harvested on a grand scale
Research showed that the amebocytes of the horseshoe crab could form a clot around as little as one part in a trillion of bacterial contamination. Not only that, but the test only takes 45 minutes to complete. Coagulan is the name of the chemical that makes this happen. Today, Coagulan is used to test medical equipment and vaccines as well as other products before they are used.
On January 12, 1973, the Food and Drug Administration declared that LAL, derived from the blood of the horseshoe crab was a biological product. Over the next several years, the FDA got feedback that enabled it to set up a database on the drug. It wasn't until 1977 that the FDA was willing to advise the use of LAL as an end-product test for medical devices, vaccines, and other medical products.
The FDA guidelines on the use of LAL as an end-product test have been revised several times over the years, the most recent being in 2012. Digital Journal's Tim Sandle wrote an interesting paper on the FDA's 2012 Question and Answer guidelines that better explains the reasoning behind the unusual steps taken to achieve compliance by the FDA.
Horseshoe crabs mating in the Delaware Bay of Southern New Jersey.
Horseshoe crabs mating in the Delaware Bay of Southern New Jersey.
During the breeding season, horseshoe crabs head for the shallower coastal waters, occasionally coming onto land. This is when the crab is harvested in vast numbers for the blood-letting that goes on. Over 600,000 horseshoe crabs are captured each year during the spring mating season so that they can "donate" 30 percent of their blood. There are only a few of the specialized facilities in the U.S. and Asia that do the harvesting. The blue blood of the horseshoe crab is worth $60,000 a gallon, fueling an industry worth over $50 million annually.
We are depleting the horseshoe crab population
Conservation of the horseshoe crab is a vital concern. Of the crabs taken for harvesting of blood and then returned to the sea, about 10 to 15 percent die. Added to this mortality figure is the 1.5 to 2.0 million harvested for food or caught unintentionally by shrimp fishermen in their nets. Another problem being found is the loss of suitable beach habitat for breeding. The shoal areas of the Delaware and Chesapeake bays are essentially the nurseries for young horseshoe crabs who will spend the first two years of their lives in these protected areas.
The bottom line cannot be dismissed. The horseshoe crab population is falling. Regardless if the decline is due to over-harvesting or the degradation of the spawning grounds due to soil erosion and pollution, it seems ridiculous that an animal that has managed to survive for so long on this planet should now be facing a decline in numbers.
More about horseshoe crabs, blue blood, Limulus Amebocyte Lysate, Unsanitary conditions, FDA regulations
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