The flesh-eating New World screwworm has been detected in South Texas, marking the parasite's return to the U.S. decades after it was eradicated nationwide.
The U.S. Department of Agriculture confirmed the case Wednesday evening. USDA Secretary Brooke Rollins said the detection involved a three-week-old calf in Zavala County, about 60 miles from the U.S.-Mexico border.
The confirmation came hours after the federal agency said it was working to confirm the suspected case through laboratory testing in Iowa. No other cases have been reported, Rollins said.
The New World screwworm is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals, including cattle, wildlife, pets and, in rare cases, humans. Left untreated, infestations can cause severe injuries and death.
Federal officials stressed that the U.S. food supply remains safe. According to the USDA, screwworms don't infest meat, fruits, vegetables or other food sources.
Authorities have responded to the case by forming a quarantine zone around the detection site, increasing surveillance and trapping efforts, and accelerating the release of sterile screwworm flies designed to prevent the pest from reproducing.
The parasite was eradicated from the United States in the 1960s through a program that released sterilized male flies to stop the species from reproducing. The effort pushed the pest south, but in recent years it has steadily spread back north through Mexico, prompting state and federal officials to closely monitor its advance toward the U.S. border.
Earlier this week, the U.S. Department of Agriculture reported a confirmed case in the Mexican state of Coahuila, roughly 25 miles south of the Texas border.
The confirmed case marks a significant development for Texas livestock producers and wildlife officials, who've spent months preparing for the possibility that the parasite could cross into the state. The state already launched a response effort earlier this year, including plans for a new $750 million facility in South Texas aimed at preventing the parasite's spread.
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