Engineering Execution: Colossal’s Radical Plan to End the Screwworm Crisis

Colossal Biosciences made its name promising the impossible in reverse — pulling the woolly mammoth, the dodo, and the dire wolf back from the far side of extinction. So there's a strange symmetry in its newest ambition: this time, the Dallas biotech wants to push a species into the void, on purpose. The target is the New World screwworm, a flesh-eating parasite that just resurfaced in a Texas calf for the first time since 1966 — and that ranchers fear could tear through a national cattle herd already stretched to its breaking point.

The screwworm is exactly as grim as it sounds. Females lay their eggs in open wounds; the larvae hatch and chew into living flesh, and an untreated infestation can kill a full-grown steer.

For 60 years, the United States has held the fly at bay with a single laborious trick — raising millions of male flies, sterilizing them, and releasing them so wild females, who only breed one time in their entire life, mate but produce nothing. It works. It also never stops, demands an endless supply of flies, and, according to frustrated officials this week, moves too slowly to outrun a fast-moving outbreak.

Colossal thinks the approach would benefit from an injection of modern technology.

What makes its plan genuinely radical isn't the speed. It's the premise. Rather than flooding the world with flies forever, Colossal wants to reach into the screwworm's DNA and rig the most basic rule of inheritance. Normally, a new trait has a coin flip's chance — fifty-fifty — of reaching the next generation. A gene drive weights that coin so it lands the same way nearly every time, forcing an engineered edit into almost every offspring.

Aim that edit at female fertility, and each generation carries more daughters that cannot breed — until the arithmetic turns against the species and the population simply runs out of mothers. Colossal calls it "genetic biocontrol." In plain terms, it's an extinction the fly builds into itself, one the company believes could empty an infested zone in a year instead of decades.

The argument is as much economic as biological.

“The New World screwworm is advancing faster than existing control efforts can keep pace, and relying indefinitely on decades-old methods like mass sterile insect releases is an increasingly costly and unsustainable strategy,” said Ben Lamm, CEO and co-founder of the Texas-based Colossal Biosciences. “Through Colossal’s next-generation genetic biocontrol technologies, we now have the ability to safely, precisely, and efficiently eliminate screwworm populations. To prevent a widespread outbreak that threatens livestock, wildlife, food security, and the economy, we must act now before the screwworm decimates the U.S. cattle industry.”

For years, Colossal's whole promise has been that extinction doesn't have to be permanent. The screwworm turns that promise inside out. Here is one species the company would like to make permanently gone — and, for once, it's betting the world will agree that some things are better off staying that way.