Turns out that the blood of horseshoe crabs has some components that are superb at detecting infection. The blue-colored blood of horseshoe crabs was selling for $14,000 per quart, and the crabs were in danger of being wiped out in certain of their long-time habitats.
Now Sarah Zhang offers an update in "The Last Days of the Blue-Blood Harvest," appearing in The Atlantic (May 9, 2018). The subtitle reads: "Every year, more than 400,000 crabs are bled for the miraculous medical substance that flows through their bodies—now pharmaceutical companies are finally committing to an alternative that doesn't harm animals. Zhang writes:
"Contemporary humans do not deliberately kill the horseshoe crabs—as did previous centuries of farmers catching them for fertilizer or fishermen using them as bait. Instead, they scrub the crabs clean of barnacles, fold their hinged carapaces, and stick stainless steel needles into a soft, weak spot, in order to draw blood. Horseshoe crab blood runs blue and opaque, like antifreeze mixed with milk. ... Horseshoe-crab blood is exquisitely sensitive to toxins from bacteria. It is used to test for contamination during the manufacture of anything that might go inside the human body: every shot, every IV drip, and every implanted medical device. So reliant is the modern biomedical industry on this blood that the disappearance of horseshoe crabs would instantly cripple it."Jeak Ling Ding and her husband and research partner Bow Ho from the National University of Singapore started a quest to find an alternative. After a number of false starts over a couple of decades, they had identified the gene for "factor C," which is the key to detecting infection, and spliced it into "insect gut cells, turning them into little factories for the molecule. Insects and horseshoes have a shared evolutionary lineage: They’re both arthropods. And these cells worked marvelously."
The scientific discovery was in the late 1990s, but the wheels of medical innovation can grind slowly. It took until 2003 for the first test kit to come out. But for a decade, there was only one supplier. Regulators like the Food and Drug administration seemed ambivalent about whether the new technology would be acceptable. Existing companies using horseshoe crab blood had no reason to switch. Pharmaceutical companies were risk-averse, too. It's not until the last few years that more suppliers have entered the market, and regulators and drug companies are opening up to the switch.
In one of those ironic turns, medical technology first imperiled the horseshoe crab, but gene-splicing technology may end up saving it. Sometimes the answer to problems created by one technology is an alternative technology.