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News
The flesh-eating New World screwworm has now infected its first horse in the U.S., detected in Presidio County, Texas. Authorities have banned the movement of warm-blooded animals outside a designated "infested" zone. The outbreak, which began in cattle earlier this year, could cost Texas up to $1.8 billion if it spreads widely.
The New World screwworm — a parasitic fly whose larvae burrow into living flesh — has now been confirmed in a horse for the first time in the United States, detected in Presidio County, Texas, near the Mexican border. The Texas Animal Health Commission responded swiftly, issuing a movement ban on warm-blooded animals outside a designated "infested" zone covering Presidio and Jeff Davis counties.
This marks a troubling escalation of an outbreak that has been building for months. The parasite was first confirmed in U.S. cattle in early June 2026, and cases have since climbed to at least 15 animals across Texas and New Mexico. The U.S. and Mexico have been racing to contain the spread, including inaugurating a joint $50 million sterile fly production plant in Chiapas in June — though experts say even the combined output of existing and planned facilities falls short of the 600 million sterile flies per week needed for full eradication.
By the Numbers:
Why it matters: The expansion of screwworm to horses signals the parasite is broadening its host range in the U.S., raising urgent concerns for the equine community and livestock industries alike. With sterile fly supplies still insufficient and key USDA staffing gaps, the path to containment remains uncertain.
