Horseshoe Crabs & Vaccine Research

A species present for over 450 million years, horseshoe crabs are older than dinosaurs. In the medical community, these animals are known for their bright blue blood, which contains immune cells that show extreme sensitivity towards toxins. Once the immune cells in the blood encounter toxins, the cells clot and encircle the endotoxins, preventing any potential infection from spreading. This discovery led to the Limulus Amebocyte Lysate (LAL) test. The LAL test relied on horseshoe crabs' toxin sensitivity to detect potential endotoxins (toxins present inside cells) before vaccine distribution. The LAL test was a massive breakthrough in vaccine quality checks. The test was "3 to 300 times more sensitive" than previous vaccine contamination tests (D’avella, 2021).

Nevertheless, vaccine testing harms the horseshoe crab population, as about 15% of crabs die after blood collection. Furthermore, the loss of horseshoe crabs is detrimental because of their significant impact on ecosystems. Horseshoe crab shells serve as micro-ecosystems for microorganisms, the crabs nourish sediment health along the coastline, and their eggs are primary food sources for birds and fish. When incorporating animals into medical research, human intervention and accountability are necessary to ensure adequate care and humane handling for animal well-being. It is through this that ethical animal involvement can occur in medical research.

Fortunately, efforts toward the horseshoe crabs' safety have been made through implementing better methods to reduce mortality during blood collection, manufacturing synthetic alternatives to the crabs' sensitive blue blood, and the recent push in 2019 for legislation to protect horseshoe crabs.

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References

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Chen, C.-P., Yeh, H.-Y., & Lin, P.-F. (2004). Conservation of the horseshoe crab at Kinmen, Taiwan: strategies and practices. Biodiversity and Conservation, 13(10), 1889–1904. SpringerLink. https://doi.org/10.1023/b:bioc.0000035868.11083.84

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D’avella, J. (2021, September 8). Paleozoic Paladin: Horseshoe Crabs and their Contribution to Vaccine Research. Cpp-College.netlify.app; The College of Physicians of Philadelphia. https://collegeofphysicians.org/programs/education-blog/paleozoic-paladin-horseshoe-crabs-and-their-contribution-vaccine-research

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Maloney, T., Phelan, R., & Simmons, N. (2018). Saving the horseshoe crab: A synthetic alternative to horseshoe crab blood for endotoxin detection. PLOS Biology, 16(10), e2006607. https://doi.org/10.1371/journal.pbio.2006607

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Pavid, K. (2021, January 15). Horseshoe crab blood: the miracle vaccine ingredient that’s saved millions of lives. Www.nhm.ac.uk; Natural History Museum. https://www.nhm.ac.uk/discover/horseshoe-crab-blood-miracle-vaccine-ingredient.html

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Sargent, W. (2021). Crab wars : a tale of horseshoe crabs, ecology, and human health. Brandeis University Press. (Original work published 2023)

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The Horseshoe Crab. (2023). » Biomedical Use of Horseshoe Crabs | The Horseshoe Crab. The Horseshoe Crab. https://horseshoecrab.org/biomedical-use-of-horseshoe-crabs/