A fresh case of the New World screwworm parasite has been detected near the U.S. border, intensifying a growing agricultural and biosecurity concern for ranchers on both sides. In Sabinas Hidalgo, in the Mexican state of Nuevo León, authorities confirmed that an eight-month-old calf transported from Veracruz was infected—a location less than seventy miles from Texas.

Mexican officials responded swiftly, declaring the case ‘‘isolated’’ and asserting that no adult screwworm flies were captured in surveillance traps in the surrounding region. Nonetheless, the discovery marks the northernmost known instance in the current wave of screwworm resurgence.

The parasite, Cochliomyia hominivorax, lays eggs in wounds of warm-blooded animals; its larvae burrow into living tissue, causing grievous harm if left untreated. After years of containment south of Mexico, the pest has advanced northward over recent seasons, undermining the U.S.–Mexico cattle trade and prompting import suspensions. Mexico reports more than 5,000 animal infections as of mid-August—an increase of roughly 53 percent over the prior month.

The United States, though uninfected to date, maintains strict vigilance. The U.S. Department of Agriculture has kept livestock imports from Mexico shuttered since early May and pledged a multi-pronged defensive strategy. Central to the plan is construction of a sterile fly dispersal facility in Texas, investment in Mexico’s fly-sterilization capability, intensified border surveillance, and deployment of advanced traps and monitoring systems.

Tension is mounting in bilateral trade dynamics. U.S. officials have criticized Mexico’s handling of recent outbreaks near the border, citing gaps in cattle movement control and monitoring. Mexico, in turn, emphasizes that it is following agreed inspection protocols, including frequent trap checks and a dual-inspection system for livestock origins.

In Texas, ranchers are watching closely. Many now brace for contingency measures should the parasite breach the border. For decades, the U.S. has lived free of screwworm, but the virus’s return would threaten not only farm incomes, but also livestock health, trade stability, and food supply systems across the region.