The New World screwworm fly has returned to south Texas. The U.S. Department of Agriculture confirmed a case involving a three-week-old calf in LaPryor, Texas, closer to the Mexico border. The parasite, known for its flesh-eating larvae, hasn’t been a threat in decades.
Quarantine Measures
Texas State Veterinarian Bud Dinges placed a 12-mile quarantine around the affected area. This measure restricts the movement of warm-blooded animals, including pets, outside the zone without an inspection. With no other reported cases in the U.S., officials highlighted that the larvae pose no risk to food. Proper treatment should help the infested calf recover.
History and Prevention
Agriculture Secretary Brooke Rollins and others have warned of the fly’s progression from Mexico, emphasizing historical economic losses from previous infestations. This case is the first in Texas since 1966. Efforts to prevent the fly’s return involved releasing sterile screwworm flies in the region to reduce wild populations.
No Mass Infestation Risk
Rollins expressed confidence in the current measures, stating there is no risk of mass infestation. The USDA’s preparations are evident as Rollins reassured, “there is no reason to believe this incursion will result in establishment of the pest in our country.”
Continued Vigilance
The USDA held a briefing about the threat when cases in Mexico were as close as 25 miles from the U.S. border. The screwworm fly, which survives in tropical climates, was confined to Panama until 2024.
The fly lays eggs in wounds, developing larvae that consume flesh, risking livestock, pets, and even humans. Infestations, without treatment, can be fatal. Past outbreaks include a Maryland case in 2025 and one in the Florida Keys, contained early in 2017.
New Facilities and Efforts
The USDA is boosting efforts with a $21 million investment to convert a fruit-fly facility in Mexico for screwworm flies and has initiated construction of a $750 million screwworm factory in Texas. The converted facility is expected to be operational next month. Additionally, they set up 8,000 fly traps along the border and have tested numerous fly samples.
Border and Community Response
Rollins recently closed the border to livestock imports from Mexico. Officials warned that the fly could travel with people, pets, and wildlife, though it does not naturally travel great distances.
Dinges urged ranchers and pet owners in the quarantine zone to cooperate. “Please help us prevent any further movement of this pest by staying put,” he stated.
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