USDA Detects First Screwworm in U.S. Cattle Since 1982; $750M Facility Already Funded to Triple Sterile-Fly Production

U.S. cattle since 1982. A second case was confirmed Friday about six miles from the first site.

The New World screwworm is a species of blowfly native to the southern United States. Female flies are attracted to open wounds, where they lay 200 to 300 eggs. The larvae that hatch resemble wood screws and use specialized mouth hooks to tear into flesh and burrow deeper.

Unless larvae are removed and animals receive larvicide and antibiotics, infections are typically fatal. For humans the condition is extremely painful, though uncommon. The fly cannot survive winter temperatures.

The United States began an eradication campaign in the late 1950s. Factories and dispersal sites in Florida, Texas and Central America released hundreds of millions of sterile male flies each week. Because females mate only once, the sterile males created reproductive dead ends.

Cases in the United States reached zero in 1982, and the campaign continued southward until the pest was eliminated past the Panama Canal around 2004. As eradication advanced, northern production facilities closed. The only remaining sterile-fly plant is now in Panama.

In 2023 an outbreak began moving north from the Darién Gap, first through Panama and Costa Rica, then Mexico, and now into Texas. The USDA is spending $750 million to construct a new Texas facility that will produce about 300 million sterile flies per week, roughly three times current capacity. The plant is not expected to open before late 2027.

8 billion annually in livestock deaths, veterinary care and labor, according to 2024 USDA estimates. Until the new facility is operational, the risk of further spread remains elevated. In 2024 a group of bioethicists, conservation biologists and scientists met to consider whether genetic modification could be used to drive the species to extinction.