advertisement

Infectious Diseases

Updated 08 June 2020

This animal’s blue blood is going to be in high demand to test coronavirus vaccines

The horseshoe crab’s special blue blood is used to test intravenous drugs for bacterial contaminants.

  • The blood of the horseshoe crab is used to test the safety of vaccines
  • There is an alternative test that's more animal friendly
  • The numbers of horseshoe crabs have been declining


As the world races towards a vaccine for the potentially deadly Covid-19 virus, one key substance is set to become highly sought after.

The unique blue blood of the horseshoe crab is used in a vital process that checks whether or not intravenous drugs – like vaccines – have any antibacterial contaminants, to ensure they're safe for humans.

And as pharmaceutical companies rush to test vaccines for the deadly coronavirus, demand for its blood is set to surge, according to the New York Times.

It has been used in the pharmacological industry for almost 50 years. According to a study of the ancient creature, its blood contains amebocytes - a mobile cell that defends against pathogens and is highly susceptible to endotoxins. These form part of bacteria that could lead to toxic shock or cause severe fever.

The extract from the blood is called limulus amebocyte lysate (LAL), and when added to medicine, it will thicken solutions contaminated with bacteria. Otherwise, the medicine continues its normal flow through the process. 

But what about the crabs? The harvesting practices and use of their blood have been hotly contested in the industry by conservationists, especially as an alternative test was developed 15 years ago called recombinant Factor C (rFC). 

It’s a synthetic equivalent grown in a lab, and while it’s accepted as a viable alternative in Europe, laboratories have to jump through extra hoops in the US if they use rFC instead of LAL according to wildlife conservation organisation Revive & Restore that focuses on the biotechnology field.

horseshoe crab infographic

Initially, the US Pharmacopeia – which has worldwide influence – had been working on putting rFC and LAL on an equal footing for approval of medicine, but backtracked at the end of May, scrapping the process and making rFC a separate charter to LAL, making it more arduous for companies to use the alternative. 

The New York Times reports that despite the expected surge in demand, companies that make LAL say that supplies of the crab blood are still adequate to handle the increase for now. Very little of the horseshoe crab’s blood is required to perform the tests, which are used multiple times during the medicine manufacturing process. 

Revive & Restore, alongside other organisations, launched a new partnership at the start of June – The Horseshoe Crab Recovery Coalition – which aims to implement best practices for the bleeding of horseshoe crabs and promote the use of rFC.

The populations of horseshoe crabs in North America are on the decline, and their smaller numbers have a knock-on effect on shorebirds dependent on the crab’s eggs.

Image credit: Pixabay