Every April in South Carolina, fishermen catch hundreds of horseshoe crabs as they crawl onto shore to mate. The crabs are transported to labs owned by Charles River, an American pharmaceutical company, in Charleston. There they are strapped to steel countertops and, still alive, drained of about a third of their blue-colored blood. Then they are returned to the ocean. This liquid is vital for America’s biomedical industry. A liter of it goes for as much as $15,000. Bleeding is not without harm to the crabs. Conservationists estimate that between 5% and 30% of them die on release…In 2016 the International Union for Conservation of Nature listed them as “vulnerable” to extinction… 

Parts of modern medicine have been unusually reliant on the horseshoe crab. Its blood is the only known natural source of limulus amebocyte lysate (LAL), an extract that detects endotoxin, a nasty and sometimes fatal bacterium. Drug firms use it to ensure the safety of medicines and implanted devices, including antibiotics, anti-cancer drugs, heart stents, insulin and vaccines. The immune cells in the crab’s blood clot around toxic bacteria, giving a visual signal of unwanted contamination. As pharmaceutical companies ramped up production of the covid-19 jab, demand for the blue liquid soared. In 2020 nearly 650,000 crabs were bled in America, 36% more than in 2018.

As crab numbers fall and demand for LAL rises, America’s biomedical industry will face a crunch. Yet a synthetic alternative to LAL is already available and used in China and Europe.

Excerpt from In America, crab blood remains vital for drug- and vaccine-making, Economist, Sept. 3, 2022