USDA Reports New Cases of New World Screwworm, Accelerates Eradication Efforts

The U.S. Department of Agriculture (USDA) confirmed three new cases of New World screwworm, including the first reported infections in dogs and goats, on Monday, raising the national case count to five. The agency pledged to intensify mitigation strategies, including deploying artificial intelligence (AI) monitoring, expanding sterile fly production, and exploring an emergency authorization for a genetically engineered fly strain.

New Cases Highlight Resurgence of Eradicated Pest

The latest cases were identified in a calf in La Salle County, Texas; a goat in Gillespie County, Texas; and a dog in Lea County, New Mexico. While the dog’s travel history remains unclear, officials initially suspected it may have been exposed in Mexico before later stating its movement patterns were unknown. The USDA had previously reported two calf cases in Zavala County, Texas, last week.

Secretary of Agriculture Brooke Rollins acknowledged the re-emergence was not unexpected, citing the parasite’s northward movement through Central America over recent years. “Every model showed that the New World screwworm would be here in Texas by early last summer, so we bought ourselves an additional year to prepare for this moment,” she said.

Mitigation Strategies Include AI, Sterile Flies, and Genetic Innovation

Federal and Texas officials are leveraging AI to track screwworm populations, training ranchers to identify infections, and expanding facilities that produce and release sterile male flies. The sterile insect technique, which eradicated the pest from the U.S. in the 1960s, relies on releasing sterile males to reduce reproduction. However, separating males from females in mass production has proven inefficient, leading to the development of the NovoFly strain.

NovoFly, a genetically engineered screwworm, contains genes that cause female embryos to die unless an antidote (tetracycline) is administered. This allows only sterile males to reach adulthood, potentially doubling the number of sterile flies released. “It’s going to allow us to almost instantaneously double the number of sterile flies that we put in the fight,” said Scott Hutchins, under secretary for research at the USDA.

Emergency Authorization for NovoFly Under Review

The Environmental Protection Agency (EPA) is considering an emergency exemption to expedite NovoFly’s release, given the public health and economic risks of an outbreak. If approved, the strain could become one of the few genetically engineered animals released into the wild, following precedents like the Oxitec mosquito and modified pink bollworm. However, field testing remains pending, according to Maxwell Scott, an entomologist at N.C. State University who contributed to NovoFly’s development.

“It’s never been tested in the field, and that has to be the next step,” Scott said. The USDA has emphasized its commitment to pursuing all viable strategies, including NovoFly, to achieve eradication ahead of the 2027 spring season.

Historical Context and Public Health Implications

The New World screwworm, a blowfly that lays eggs in open wounds, can kill animals within a week if untreated. While human infections are rare, a travel-related case was confirmed in Maryland in 2025. The USDA’s 2017 eradication of a Florida Keys outbreak using sterile insects remains a key precedent. Gov. Greg Abbott of Texas reiterated confidence in the agency’s approach, stating, “We prevented and eradicated this pest before. We can do it again.”