US Shuts Border Again as Flesh-Eating Fly Spreads North

The United States has once again closed its southern border to livestock imports after discovering that a dangerous parasite has spread farther north in Mexico than initially believed by experts. The parasite, known as the New World screwworm fly, poses a serious threat to cattle and other animals. Its larvae are notorious for feeding on the live flesh of warm-blooded animals, which can lead to severe wounds and even death if not treated quickly.

American officials are especially worried that the fly could cross into Texas, a state with a major cattle industry. The United States Department of Agriculture (USDA) remembers the economic damage the pest caused decades ago before it was largely eradicated in the 1970s. Back then, scientists successfully used a method of breeding sterile male flies and releasing them into the wild to interrupt the reproductive cycle. Since then, the parasite was mostly contained in Panama and Central America until detections began in southern Mexico around late 2024.

Just last month, the USDA began reopening some ports of entry after closing the border in May. But the recent report of an infestation approximately 185 miles northeast of Mexico City, about 370 miles from the U.S. border, changed those plans; this detection lies roughly 160 miles farther north than earlier cases, significantly closer to Texas.

USDA Secretary Brooke Rollins announced the new closure, praising the quick work of inspectors in both countries. “Thanks to aggressive monitoring by USDA staff, we’ve been able to take decisive action to stop the spread of this deadly pest,” Rollins said.

In Mexico, President Claudia Sheinbaum criticized the U.S. decision as “exaggerated,” asserting her government is following established containment protocols, and noting that animal infection figures reported at 392 cases are down nearly 19% since June 24.

Meanwhile, the USDA is investing roughly $29.5 million to fight the parasite, including an $8.5 million sterile fly dispersal facility in Texas and a $21 million renovation of a facility in southern Mexico, with operations expected to begin by mid‑2026.

Lawmakers in the United States are also pressing for faster approval of anti-parasite treatments to protect livestock in case the pest gets closer to America.