Flesh-eating Screwworms Have Returned. Which New Technologies Could Stop Them

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• Mario Aguilera - [email protected]

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They may look like any ordinary species of flies buzzing around on a given day, but the New World screwworm is quite extraordinary. Screwworm flies are highly destructive parasitic flies that feed on the tissue of warm-blooded animals, including humans (though the risk to humans is low). They burrow their way in a spiral (screw) pattern into wounds and bodily openings such as the ears, nose and mouth, laying hundreds of eggs.

The flies were well known in the 1960s and 1970s for inflicting hundreds of millions of dollars in losses on the livestock industry while causing widespread animal suffering before they were eradicated. Screwworms have now re-emerged in parts of Central and North America, including recently confirmed cases in Texas and New Mexico in cows, goats and sheep.

To put the issue in perspective, we turned to University of California San Diego Department of Cell and Developmental Biology Professor Omar Akbari, who studies insect genetics and has developed several technologies designed to suppress insect populations. His lab recently received government funding to develop safe, rapidly deployable technologies to protect U.S. agriculture and ecosystems from invasive species that threaten the nation's economy and security.

Q: As the New World screwworm returns to North America, which new technologies could help control the outbreak?

The New World screwworm was once considered one of the greatest pest-eradication success stories in history. A coordinated international campaign eliminated the pest from the United States and much of Central America, protecting livestock while preventing immense animal suffering. After decades of successful control, it has re-emerged across Central America and Mexico and has recently been detected again in parts of the United States.

That resurgence is raising concerns for livestock producers, wildlife managers and public health officials. The stakes are high. The New World screwworm threatens the U.S. livestock industry, and historical analyses have estimated that widespread outbreaks could result in billions of dollars in economic losses while causing significant animal suffering.

One of the most promising developments is our growing ability to understand the screwworm at the genetic level. Scientists have sequenced its genome in unprecedented detail, helping us identify genes involved in reproduction, development and host-seeking behavior. Researchers are also learning more about how screwworm flies locate animals and wounds through chemical cues. Together, these advances can improve surveillance and monitoring efforts while helping researchers design more targeted control strategies.

Importantly, the original screwworm eradication campaign was not achieved through a single technology. While the sterile insect technique (SIT) - which controls pest populations by releasing sterile male flies that cannot produce offspring - played a central role, success also depended on surveillance networks, livestock treatment programs, animal movement restrictions, population monitoring and sustained international cooperation. In many ways, the lesson from that success is that no single tool solves the problem on its own.

Today's response builds on that same principle by combining immediate control measures with investments in next-generation technologies. While current efforts rely on proven approaches such as surveillance, treatment programs and sterile insect releases, researchers are also working to expand the range of options available should future outbreaks grow in scale or complexity.

Many of the technologies highlighted in the review build on that principle. One of the most advanced examples is a genetically engineered male-only screwworm strain known as NovoFly. This strain builds on a technology originally developed more than 25 years ago and has been adapted and refined for screwworm control over the past decade. NovoFly is engineered so that female flies do not survive to adulthood, producing only male flies for release. NovoFly is currently undergoing regulatory review for emergency use in response to the ongoing screwworm outbreak.

Researchers are also developing technologies that make it easier to separate male and female flies, helping sterile insect programs become more efficient and less expensive. One example is SEPARATOR, a genetic sex-sorting technology that enables the efficient separation of males from females during mass rearing, reducing production costs and helping scale sterile insect programs. Other approaches use gene-editing tools such as CRISPR (clustered regularly interspaced short palindromic repeats) to produce sterile males without using radiation, potentially making them better able to survive and compete after release.

Looking further ahead, emerging technologies such as precision-guided sterile insect techniques (pgSIT), which our laboratory previously demonstrated as a powerful genetic population-control strategy, and other advanced genetic population-suppression technologies may provide additional tools for regional population suppression. While these approaches remain at different stages of development and regulatory evaluation, they illustrate the expanding range of options that could complement existing screwworm control programs in the future.

While some of these technologies remain under development, others are already moving toward real-world implementation. They have tremendous potential to become important components of future screwworm control programs, helping ensure that decision-makers have a broader set of evidence-based options available if the threat continues to expand. I don't see them replacing the proven strategies that successfully eliminated screwworm from the United States decades ago. Instead, I see them as complementary technologies that can improve surveillance, increase efficiency and strengthen long-term control and eradication efforts.

The recent resurgence of screwworm reminds us that successful pest control requires continued vigilance and innovation. By combining modern advances in biotechnology with the lessons learned from one of the world's most successful pest-eradication programs, we have an opportunity to build a stronger and more sustainable toolkit for protecting livestock, wildlife and public health throughout the Americas.

Resurgence of the New World Screwworm and the Future of Genetic Biocontrol (Trends Open, July 23, 2026)

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