The Trump administration has warned that New World screwworm larvae are being detected closer to the U.S. border, though federal data says the pest is not currently present in the United States and there are no confirmed domestic infestations. Agriculture Secr
The alarm didn’t come with sirens or shutdowns. It came with a virtual briefing call and a warning that sounded urgent even before the details were fully laid out: New World screwworm—a parasite whose larvae can eat living flesh—has been showing up increasingly close to the U.S. border.
On Tuesday afternoon, U.S. Agriculture Secretary Brooke Rollins posted on X that officials are closely tracking the fast-moving outbreak as it advances through Mexico. She said she held a “virtual NWS briefing call with over 700 attendees from media to stakeholders to elected officials” to deliver an update on the threat “as it nears our southern border.” She added that the administration is seeking to keep the public informed in real time “shutting down rumors” and “laying down the facts” about what officials and state partners are doing to protect American agriculture. livestock. and wildlife.
Federal officials say New World screwworm is not currently present in the United States. and there are no confirmed domestic infestations. Still. they are watching confirmed detections move closer to the border in recent months. including cases documented within a few hundred miles of Texas—an approach that has sharpened worry among agriculture officials and policymakers.
The United States eradicated the screwworm in the 1960s. But the outbreak reemerged in Panama and Costa Rica in 2023 and has since spread through all countries in Central America and into Mexico. where thousands of animal cases have been reported. Rollins’ warning lands against that backdrop: a pest that was wiped out once before, then returned and kept moving north.
The concern is not abstract. The New World screwworm is a parasitic fly whose flesh-eating larvae hatch in open wounds and feed on living tissue. Unlike many other maggots that feed on dead tissue. screwworm larvae consume healthy flesh. making the infestation especially destructive and potentially lethal for animals if not treated quickly.
Federal officials have also said they are tracking the northward movement through surveillance programs that include regular updates on detections within several hundred miles of the U.S. and coordination with Mexican authorities to contain the spread. To prevent entry into the United States, agencies are using containment measures, most notably the release of sterile male flies. The technique works by disrupting the reproduction cycle: females that mate with sterile males produce no viable offspring. gradually collapsing the population.
Officials have restricted livestock imports from affected regions and are working with partners to monitor outbreaks and prevent the parasite’s spread. The risk, officials say, largely comes from animal movement. Infected livestock, wildlife, or even pets can carry larvae into new areas, allowing the parasite to spread geographically.
Rollins’ post came as other warning signals have appeared from the Texas political sphere. On June 1, Texas State Representative Don McLaughlin issued an urgent call to action claiming the destructive pest had been identified within one mile of the Texas border.
Even as officials stress that there are no confirmed U.S. infestations, the threat carries a second kind of public fear: whether people could be affected. The screwworm primarily targets livestock and wildlife, but humans can become infected in rare cases. The infestation is known as myiasis and occurs when flies lay eggs in an open wound or body opening. When the eggs hatch, larvae burrow into the tissue and begin feeding on living flesh, causing painful, progressively worsening wounds. In severe instances, untreated infestations can lead to extensive tissue damage and secondary infections.
Symptoms can include unexplained, painful wounds or sores that do not heal; a foul-smelling odor or bleeding from the site; and seeing maggots or feeling movement in open wounds or sores, including areas of the body such as the nose, mouth, eyes, ears, or genitals.
There has been at least one travel-associated case in the United States. The case occurred in August 2025 after a patient returned to the U.S. following travel to El Salvador. Officials advise people traveling to impacted areas to keep wounds clean and covered and to seek medical care if signs of infestation occur.
In the background is the scale of what screwworm outbreaks can do to the U.S. economy if they take hold again. The USDA has said eradication from the U.S. is estimated to save the U.S. livestock industry $900 million per year. That figure—tied to decades of work that succeeded in eliminating the pest—helps explain why officials are treating the latest detections as more than a border story.
What happens next, federal officials warn, could be costly. A renewed outbreak could disrupt livestock production, trigger trade restrictions, and require expensive eradication campaigns. Protecting the agricultural sector is a top priority. they say. because even a limited outbreak could create significant economic and supply-chain impacts.
At the moment, the screwworm remains outside U.S. borders. But as the pattern of confirmed detections pushes northward—past previous landmarks and toward Texas—the administration’s message is clear: decades-long progress can be fragile, and the window to stop the next wave is narrow.
New World screwworm flesh-eating larvae Brooke Rollins USDA Texas border sterile male flies myiasis agriculture threat Mexico outbreak wildlife and livestock