Sydney Heidtmann ‘22
October 2020

A miracle substance in horseshoe crab blood may hold the key to engineering a safe and effective vaccine for the novel COVID-19 virus, according to scientists. Though the prospect has drawn no small amount of opposition from conservationist groups concerned about the declining horseshoe crab population.

Horseshoe crabs have become increasingly important to the biomedical industry due to their primitive immune-like responses to bacteria. Their blood contains a substance called Limulus Amebocyte Lysate (LAL), which reacts with endotoxins in cells to find and measure bacterial toxins in the blood. This natural process is one of the main reasons that horseshoe crabs have survived for hundreds of millions of years. Over the past four decades, scientists have found a way to apply this chemical process to modern medicine.

Throughout the engineering stage, scientists have to ensure that there are no dangerous bacteria present in vaccines. This is where LAL comes in. Scientists can use something called the “LAL test” to detect harmful toxins in newly developed vaccines. When this test is performed, the solution will clump up, or change in color to indicate the presence of toxins in vaccines. Scientists believe this technique will be useful in clearing a potentially dangerous drug such as a vaccine for COVID-19.

Because LAL is unique to horseshoe crabs, they are a crucial resource for drug companies. Over forty thousand of them are harvested and bled annually in American labs. This bleeding process has led to a steady decline in the horseshoe crab population over the past couple of decades. Initially, scientists believed that nearly all horseshoe crabs returned to their natural habitats unharmed after being bled.

However, in recent years it has been estimated that up to 30% of horseshoe crabs do not survive being “bled”. There is also a theory that blood loss can cause females to be less likely to mate. This would lead to lower reproduction rates which in turn would contribute to population decline. Drug companies will have to bleed even greater numbers of crabs if they plan on using LAL to clear the Coronavirus vaccine.

These variables could prove diasterous for ecosystems, say wildlife conservationists. Larry Niles, a conservation biologist at the Wildlife Foundation of New Jersey, is concerned about the impact bleeding might have on migratory shore birds. Birds like the Red Knots rely on horseshoe crab eggs as a vital food source. The crab's calorie-rich eggs are the perfect fuel for long distance flying. This year, the number of Red Knot birds that stayed in the Delaware Bay decreased by about 25%. The shore birds are less numerous partly due to the decreasing amount of horseshoe crab eggs, Niles says. He warns that a single weak link in the food chain could have disastrous consequences.