Horseshoe crab blood contains Limulus Amebocyte Lysate, which is used to ensure drugs, vaccines and medical devices. Shutterstock image
Can farming horseshoe crabs help the COVID-19 cause?
Wednesday, July 15, 2020, 17:00 (GMT + 9)
With RAS, medical researchers hope harvesting the species’ valuable LAL can continue with less harm done to wild stocks
Blood from horseshoe crabs (Limulus polyphemus) is a vital resource for modern medicine. It contains Limulus Amebocyte Lysate (LAL), an aqueous extract of amoebocyte cells that is used in sterility testing to ensure that drugs, vaccines and medical devices are free from potentially deadly bacteria called endotoxins. Since its approval by the U.S. Food and Drug Administration in 1977, the LAL assay has been the standard test for the contamination of medical devices by endotoxins.
The underside of a horseshoe crab tagged for research. Photo courtesy of Kepley BioSystems
However, attempts to detect such bacteria in human blood using LAL have been unsuccessful so far, due to interfering factors such as cross-reactivity and inhibitors. Meanwhile, the demand for horseshoe crab blood has raised questions over the impacts of harvesting from the wild, where approximately 600,000 crabs are removed each year. Horseshoe crabs are already vulnerable due to global warming and harvesting as bait to catch eels and whelks. Aquaculture methods have been trialled before to reduce mortalities and improve LAL supplies, but long-term efforts have been either unreported or unsuccessful.
Concerned over the pressure on horseshoe crabs in the wild and keen to develop LAL assays for human blood, a group of researchers in North Carolina recently published a new paper that could hold the key to addressing these issues.
“We wanted to find a more efficient and potentially more conservational way to harvest horseshoe crabs and transition the typical food aquaculture space into something that produces high-end biotechnology outputs with economic potential,” Dr. Anthony Dellinger, president of Kepley BioSystems, a life science start-up in North Carolina, told The Advocate.
A look at Kepley BioSystems’ RAS set-up for horseshoe crab research. Photo courtesy of Kepley BioSystems
In order to facilitate LAL harvesting and maintain animal welfare, Dellinger and his colleagues developed a recirculating aquaculture system (RAS) system of two holding tanks (4-by-6-by-1 feet, salinity 19.5 to 22.0‰), a biofiltration tank and a solids separation tank. The horseshoe crabs remain in the multi-tank setup long-term, receiving a special diet and periodically having blood drawn with an intravascular catheter that’s surgically implanted.
The team found that the horseshoe crabs maintained their natural behavior and body weight, grew consistently, survived catheter implantation and thrived for more than 12 months with a zero percent mortality rate. They also found that LAL can be extracted up to 24 times a year from horseshoe crabs that are kept in aquaculture long-term. Sufficient research and evidence also shows that horseshoe crabs can be bred and grown in captivity to replace aquaculture stock, which could potentially abolish the need to harvest them for the biomedical industry.(Continue...)
Author: Bonnie Waycott / Global Aquaculture Advocate