Flesh-Eating Parasite Returns to US After 60 Years, Threatens Livestock and Trade

The United States is confronting a severe agricultural threat with the confirmed return of the New World screwworm (Cochliomyia hominivorax), a flesh-eating parasite not seen in the country since its eradication in 1966. The first detection came in a calf in La Pryor, Texas, near the Mexican border, triggering a swift response from state and federal authorities. Within days, a second case was confirmed just nine kilometres away, in Zavala County, prompting Governor Greg Abbott to issue a disaster declaration for Zavala and Uvalde counties and mobilise all available state resources. The USDA has reinforced quarantine measures and surveillance along known cattle movement corridors, but the outbreak has already unsettled the heartland of American beef production.

The parasite's reappearance on US soil comes against a backdrop of a far larger outbreak in Mexico, where authorities recorded 2,024 active cases as of the third of June 2026, with the state of Veracruz leading in human infections. The Mexican outbreak has been building for months, despite intensified surveillance and fumigation campaigns by SENASICA, the national agri-food safety service. For Washington, the porous border with Mexico became an obvious vulnerability, and the USDA had already tightened import protocols. Yet the swift leap northward underscores the difficulty of containing a pest whose strategy centres on exploiting even the smallest wound in warm-blooded animals, including humans.

International trade disruption followed almost immediately. Canada's food inspection agency announced a temporary ban on all livestock that had been in Texas within the previous 21 days, effectively halting cattle imports from the top beef‑producing US state. Viewed from London, the ban signals a broader nervousness among trading partners about the screwworm's capacity to spread rapidly through global supply chains, a concern mirrored in European markets where analysts warn of upward pressure on steak prices if the outbreak is prolonged. The parasite's potential to devastate herds and wild populations alike has revived difficult bioethical debates as well, with some scholars arguing this is one of the few species humanity would be justified in driving to extinction.

The historical success of screwworm eradication—a decades‑long, multi‑billion‑dollar effort that relied on releasing sterilised male flies to collapse populations—once stood as a model of international cooperation. That barrier, maintained through a sterile‑fly plant in Panama, has frayed as the parasite pushes northward, possibly via legal or undocumented animal movements. The current crisis thus tests not only emergency protocols but also the durability of a half‑century‑old pest‑control architecture. Without a rapid, coordinated, and well‑funded response that reopens the sterile‑insect production pipeline, the fly could reclaim territory across the American South, with consequences reaching from the ranchlands of Texas to the dinner tables of the world.