The Current

Vaccine research threatens the health of a 'modern medical marvel' — horseshoe crabs

Conservationists are raising concerns that horseshoe crabs and the shorebirds that feed on them could become unexpected casualties of the COVID-19 pandemic.

Conservationists calling for industry to adopt alternative to using creature's blood

A unique compound in the milky blue blood of horseshoe crabs is critical to testing the safety of vaccines and other medical technology. (Mike Segar/Reuters)

Read Story Transcript

Conservationists are raising concerns that horseshoe crabs and the shorebirds that feed on them could become unexpected casualties of the COVID-19 pandemic.

"The milky blue blood of this ancient animal has made it into a modern medical marvel," David Wheeler, executive director of the Conserve Wildlife Foundation of New Jersey, said of the horseshoe crab.

The medical industry captures the critters to draw out some of their blood, because it contains a unique component called limulus amebocyte lysate, or LAL. LAL can detect harmful toxins in vaccines — including those being produced for COVID-19 — or other medicine undergoing testing, he told The Current's Matt Galloway

"It's really extraordinary," said Wheeler. "The concern now, of course, is at some point we would really like to see it shift to a synthetic alternative rather than continuing to only use the crabs for that."

The horseshoe crab isn't actually a true crab. In fact, it's more closely related to a spider or scorpion. The species is often referred to as a living fossil because it has been swimming in the seas for hundreds of millions of years — even before the time of dinosaurs.

Every spring, the species of horseshoe crabs that live in the Atlantic Ocean crawl onto North American coastal beaches to spawn, drawing a frenzy of shorebirds who feast on the critters' eggs. But horseshoe crab populations have suffered a decline in recent decades, and that's also hurting shorebird populations that rely on them to survive.

According to the Atlantic States Marine Fisheries Commission, most horseshoe crabs that are bled for medical purposes are released back into the wild, but a portion of them die from the procedure.

A 2010 study found that as many as 30 per cent die as a result — more than 10 times previous estimates, National Geographic reported.

The medical industry extracts blood from horseshoe crabs and then returns the animals to the wild. But some of the critters typically die as a result of the blood-draining process. (The Associated Press)

"Our concern is simply that there's just not a heck of a lot of transparency in this process," said Wheeler. "As a result, there's not nearly enough data for, I think, all the scientists studying this to feel confident that the [death] rates are as low as they're saying they are."

Given that the horseshoe crab population is much more vulnerable than it used to be, Wheeler worries about the medical industry's reliance on this single species for vaccine production.

If horseshoe crabs were to experience an even sharper decline, the vaccines, injectable drugs and medical devices we rely on would be left "in limbo," he said.

He suggested the medical industry should be more transparent about its practices, and adopt a synthetic alternative to the crabs' blood.

"We don't need to continue impacting this population and also making ourselves vulnerable by relying on just one species … for kind of the answer to all our prayers," Wheeler said. 

Recombinant factor C

Jay Bolden, a biologist with the pharmaceutical company Eli Lilly, has been working to make such synthetic alternatives a reality.

When he joined the company in 2000, he learned that the animals were facing a "dire situation" in parts of the world.

As an avid birder, Bolden took note and began pushing for alternatives to horseshoe blood.

"What we do have now, and what's been on the market for some time, is a synthetic version called recombinant factor C," Bolden told Galloway. 

"It's the exact same protein that is in the horseshoe crab. It's just produced by modern recombinant biotechnology processes." 

Recombinant biotechnology involves combining DNA molecules from two species, and putting them into another organism to produce new genetic combinations.

Scientists work near horseshoe crabs at Kimbles Beach, N.J. In the spring, shorebirds flock to the coastline to feast on horseshoe crab eggs. (Jacqueline Larma/The Associated Press)

Bolden said recombinant factor C is not yet widely used because the methods countries use to test medicine requires them to test for endotoxins using horseshoe crab blood.

However, this year, Europe published pharmaceutical testing methods allowing experts to use recombinant factor C to test for endotoxins, Bolden said. He added that research has proven the synthetic alternative to be safe and as effective as LAL.

"The reality is, the horseshoe crab blood has protected human health for 40 years, and certainly I can appreciate that," Bolden said. 

But he said that method comes with a cost.

"There's a better way of doing that. And that's that's exactly what we're trying to do," he said.

Written by Kirsten Fenn. Produced by Ben Jamieson.