A flesh-eating parasite once thought eradicated from the United States has resurfaced in Texas, triggering an urgent response from federal authorities and raising concerns over potential impacts on the livestock industry.
The U.S. Department of Agriculture (USDA) confirmed on Wednesday that a case of the New World screwworm had been detected in a three-week-old calf in La Pryor, South Texas. It marks the first known infection in U.S. livestock in decades.
The New World screwworm is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. Female flies lay their eggs in open wounds, where the larvae hatch and begin consuming flesh, potentially causing severe infections, organ damage and even death.
Although officials stressed that the parasite does not pose a food safety risk to consumers, experts warned that an outbreak could have devastating consequences for livestock production and the wider economy. Previous estimates suggest a major infestation could cost billions of dollars and contribute to higher beef prices.
In response, the USDA has activated emergency containment measures, including establishing a 20-kilometre control zone around the affected area, enforcing animal movement restrictions and intensifying surveillance efforts.
Authorities are also accelerating the release of sterile screwworm flies, a long-standing strategy used to suppress wild populations. The technique works by flooding affected areas with sterile male flies, preventing reproduction and gradually reducing the number of fertile insects.
USDA Secretary Brooke Rollins expressed confidence that the parasite could be contained if farmers and livestock owners follow treatment and movement-control guidelines.
The discovery comes amid a surge in screwworm cases across Central and South America, where health and agricultural authorities have been monitoring the parasite’s spread. The pest had previously been eradicated from the United States through decades of coordinated control efforts involving sterile insect programmes and international cooperation.
The parasite also poses a threat to wildlife and household pets. Veterinarians across Texas, Arizona and New Mexico have been urged to remain alert for symptoms, while pet owners have been advised to watch for unusual wounds, irritation or signs of larvae around body openings.
Human infections remain extremely rare but can be serious. The most recent U.S. case involved a traveller diagnosed in Maryland last year, who later made a full recovery.
Federal authorities have already taken several preventive measures, including tightening animal import restrictions along the U.S.-Mexico border, deploying specially trained detection dogs and expanding sterile-fly production programmes. A new facility in Texas capable of producing hundreds of millions of sterile flies each week is expected to begin operations next year.
Experts warn that while the immediate risk to public health remains low, the return of the New World screwworm represents a significant challenge for the agricultural sector and could become one of the most costly livestock threats the country has faced in decades.
