By Bianca Licitra
As concerns grow surrounding the reappearance of the New World screwworm in the United States, research universities are rising the meet the challenge, using decades of scientific research to combat the outbreak.
The New World screwworm is a parasitic blowfly native to subtropical regions of the globe. The adult flies lay their eggs on animals, where their larvae develop and burrow or “screw” into the tissue. This behavior can lead to nonhealing wounds, secondary infections, and – if left untreated – death. The U.S Department of Agriculture has now confirmed six cases of New World screwworm in the United States – five in Texas and one in New Mexico – after the outbreak spread north from Panama, Costa Rica, and Mexico beginning in 2023.
Throughout the early to mid-20th century screwworms were prevalent across the American South, killing livestock and costing livestock producers millions of dollars a year. But, in the 1950s, a pioneering research discovery led to the development of the “sterile insect technique.”
Building on the work of Nobel laureate Herman J. Muller, who studied radiation and sterilization in fruit flies at the University of Texas at Austin, two scientists worked with the USDA to develop the technique. In the 1950s, while studying the breeding practices of screwworm flies, Eward F. Kipling and Raymond C. Busland discovered that they could sterilize male screwworms with radiation but still release them to mate with female flies, resulting in unviable eggs. (They later received a Golden Goose Award for their pioneering research.)
In the years that followed, through the release of sterilized male flies into the environment, the New World screwworm was pushed out of the United States. Though the species was declared eradiated in the United States in 1966, smaller outbreaks persisted into the 1970s due to the migration of flies from Mexico, until collaborative efforts led to eradication in countries further south.
The sterile insect technique is still used today. As part of the current eradication efforts, the Environmental Protection Agency is considering an emergency measure to speed up the release of a genetically engineered New World screwworm, called NovoFly, which accelerates production of sterile males.
According to USDA estimates from 2024, a New World screwworm outbreak could cost the Texas economy alone approximately $1.8 billion dollars a year due to livestock deaths, veterinary services, extra labor, and more. Further, with U.S. cattle herd numbers at an all-time low, a New World screwworm outbreak could exacerbate the rising beef prices that consumers have already been dealing with.
As the crisis mounts, AAU institutions are partnering in multiple ways with local and federal agencies to work toward New World screwworm eradication again:
- Texas A&M University’s AgriLife program and its task force are working to support Texans with practical, science-based guidance for detecting and dealing with potential infestations. This support includes educational programs and resources for livestock producers, Texas families, veterinarians, and wildlife managers, as well as support for USDA and state agencies. Texas A&M is also supporting response and diagnostic efforts. In addition, Texas A&M System Regent John Bellinger was chosen by the Trump administration as the senior advisor for New World screwworm preparedness, which will allow him to support the USDA’s ongoing efforts.
- Last year, the University of Arizona joined the national effort against the New World screwworm when their Arizona Veterinary Diagnostic Laboratory was named one of three sites in the country to aid the USDA in screening for the pest. University of Arizona Cooperative Extension is also supporting the response through a monitoring and detection pilot program.
- A research project out of the University of Florida aims to protect food supplies in the event of a screwworm outbreak using computational models that determine how long antiparasitic drugs remain in animals’ systems after treatment.
- In California, where dairy and cattle lead the agricultural economy, the state’s Department of Food and Agriculture is funding a research project at the University of California, Riverside that is monitoring the state for early signs of the pest’s return.
Decades of federally funded, curiosity‑driven research made it possible to eradicate the screwworm from the United States in the past, thereby protecting the health and livelihoods of millions of Americans across the country. As the screwworm threat emerges again, university experts continue to build on past knowledge gained through basic research to protect farmers’ livelihoods and our food supply.
Bianca Licitra is editorial and communications assistant at AAU.