Pathologists may be interested to learn that though a substitute for horseshoe crab blood has been available for nearly 20 years, it has not been widely adopted in the US

Since the 1970s, the blue blood of the horseshoe crab has saved countless human lives by detecting deadly toxins in medical products, as well as its use in a number of medical laboratory tests. Now, that unique blood is playing a vital role in the fight against COVID-19 as well, by enabling pharma companies to ensure the coronavirus vaccines they are giving are free of bacterial contaminants—such as endotoxins—that can harm or kill patients.

Microbiologists and clinical laboratory scientists are familiar with the Endotoxin Activity Assay (EAA), which uses LAL as a way to detect if a critically-ill patient may have whole blood endotoxemia. Published studies show that the detection of elevated endotoxin activity levels is associated with an increased disease severity in patients with sepsis and septic shock.

Horseshoe crab blood is an opaque blue color due to its high copper content. The blood contains limulus amebocyte lysate or LAL (pronounced “el-ay-el”), which either clots or changes color in the presence of bacterial endotoxins. LAL has become the standard to test the safety of many medical devices and pharmaceuticals—including coronavirus vaccines. There are currently no other tests that can analyze the purity of medications and cleanliness of medical devices with the same accuracy as the LAL test.

“The crabs live only on the east coasts of Asia and North America,” Yahoo News reported. “The world’s largest population of American horseshoes winters off Maryland shores and spawns each spring in Delaware Bay. The latest trawl survey puts this population at more than 14 million mature crabs.”

Futuristic Clean Rooms for Extracting Blood

After the crabs are dredged from the ocean floor, or captured as they come ashore for breeding, they are transported to one of a handful of facilities authorized to perform the bleeding process. Once there, the horseshoe crabs are cleaned and sterilized, suspended upside down, and inserted with a needle which extracts approximately one third of their blood.

“These things are being produced in ‘clean rooms’ that look like the stuff they make microchips in,” Glenn Gauvry, Founder and President of the Ecological Research and Development Group Inc. (ERDG) told Yahoo News. ERDG is a 501(c)3 non-profit wildlife conservation organization. Its primary focus is the conservation of the world’s four horseshoe crab species.

bleeding horseshoe crabs in a laboratory for covid-19 testing chemicals
In futuristic-looking labs (above), technicians withdraw the prized blood cells from the tubular heart of the crab and then spin the blood in a centrifuge to isolate the LAL. The resulting product is then sold as endotoxin test kits to pharmaceutical companies that test medical and clinical laboratory supplies, including COVID-19 vaccines. (Photo copyright: Popular Mechanics.)

Certain laboratory tests developed from horseshoe crab blood are used to detect bacterial contamination in everything from heart stents, saline drips, and flu shots, to surgical implants such as pacemakers and prosthetic devices.

Federal law mandates that any medical device that is inserted or injected into a human body must pass the LAL test for contamination. This makes horseshoe crab blood vital for ensuring the new COVID-19 vaccinations are free of potentially-deadly toxins.

“Without LAL, you’re not going to be able to produce the billions of inoculations that are going to have to come about to handle this pandemic,” John Tanacredi, PhD, Professor of Earth and Environmental Sciences, Department of Biology, Chemistry and Environmental Studies at Molloy College, told CBS News.

A $60 Million/Year Industry

Once the LAL has been withdrawn, the crabs are returned to the wild. The horseshoe crabs typically spend one to three days in the lab while the LAL is extracted. They can survive out of water for up to four days, as long as their gills stay moist.

The crabs are then returned to the fishermen who originally caught them, to be gently placed back into the sea. “We treat these crabs like babies,” Yahoo News reported one fisherman saying. “Blue bloods save lives,” said another fisherman.

The Atlantic States Marine Fisheries Commission estimates that in 2019 labs extracted blood from approximately 640,000 horseshoe crabs in the US. Researchers estimate the industry makes about $60 million per year and that the coveted blue blood is worth about $60,000 per gallon, Yahoo News reported.

There are only four labs in the US authorized to extract blood from the horseshoe crabs. They are located in Maryland, Virginia, South Carolina, and Cape Cod. In Maryland, only three trawlers hold permits to catch the horseshoe crabs from the waters surrounding that state.

“We have a 450 million-year-old creature that for the last 45 years has improved the safety of medicines for humans and animals,” John Dubczak, Director of Operations at Charles River Laboratories, told CBS News.

Allen Burgenson, Global Subject Matter Expert-Testing Solutions, Lonza Walkersville, a division of Lonza Bioscience, told Yahoo News “the [pharmaceutical] industry produces enough tests in one day to screen five billion doses of coronavirus vaccine.”

Synthetic Substitute for Horseshoe Crab Blood Available, But Not Widely Used in US

In response to pressure from conservation groups, researchers in Singapore successfully cloned the blood of horseshoe crabs and developed a synthetic test for endotoxins. The synthetic test, known as Recombinant Factor C (rFC), has been commercially available since 2003 and in some countries in Europe is accepted as equal to tests using horseshoe crab blood. However, rFC has not yet been approved for widespread use in the US.

“You’ve got a very large, biomedical bleeding industry with a vested interest in keeping those horseshoes crabs coming in and basically protecting this monopoly,” Ryan Phelan, co-founder and Executive Director of Revive and Restore, a wildlife conservation group based in California that lobbied for the synthetic, told Yahoo News.

In 2017, Dark Daily reported on the potential threat to horseshoe crabs due to blood harvesting. In “Medical Laboratories Could Be Threatening the Survival of Horseshoe Crabs,” we noted growing concerns that the biomedical industry was having a negative impact on the horseshoe crab population. Since then, not much movement has been made toward establishing the synthetic as the standard test in the US.

Recombinant Factor C might eventually eliminate the need to harvest blood from living creatures. But for now, horseshoe crabs continue to provide a critical component for safeguarding humans against contaminants in medical supplies and pharmaceuticals, including COVID-19 vaccinations.

According to Dubczak, the LAL test “has unequivocally elevated the quality and safety of injectable pharmaceutical drugs and medical devices, and that includes all of the vaccines that protect us,” he told USA Today.

—JP Schlingman

Related Information:

How the Coronavirus Vaccine Relies on Maryland’s Strangest Fishery: Horseshoe Crabs

Horseshoe Crabs have a Vital Role in the Development of a Coronavirus Vaccine. Here’s Why

Horseshoe Crabs Help Keep Vaccines Safe. Now, They’re in Big Trouble

Endotoxin Activity Assay for the Detection of Whole Blood Endotoxemia in Critically Ill Patients

The Atlantic Horseshoe Crab and COVID-19

USP Provides Guidelines for Recombinant Factor C (rFC) a Non-animal-derived Reagent Critical to Development of Vaccines and other Sterile Pharmaceutical Products

Horseshoe Crab Anatomy

Why This Crab’s Blood Could Save Your Life

Saving the Horseshoe Crab: A Synthetic Alternative to Horseshoe Crab Blood for Endotoxin Detection

Medical Laboratories Could Be Threatening the Survival of Horseshoe Crabs