The Agriculture Department has confirmed the presence of the New World screwworm in a 3-week-old calf in La Pryor, Texas. This marks the first occurrence in U.S. cattle since the 1960s.
The New World screwworm fly, whose larvae consume the tissue of animals, was first detected at the Guatemalan-Mexican border in 2024. Upon confirmation of the screwworm case this Wednesday, Agriculture Secretary Brooke Rollins announced swift measures to contain and eradicate the pest in South Texas.
Officials worry that additional cases could severely impact the American cattle industry if left untreated. Although the screwworm was eradicated from North and Central America by the mid-2000s, it has been moving north, last seen on Mexico’s border with Guatemala in 2024.
Screwworm flies typically do not travel far but can spread if infected animals are transported. Mexico has already reported over 20,000 cases. U.S. officials have barred Mexican cattle from entering the country for over a year as a precaution.
The Agriculture Department assures that the screwworm doesn’t affect fruits or vegetables. Food Safety and Inspection Service will ensure beef, poultry, and eggs remain safe for consumption.
A 20-kilometer quarantine zone has been announced where the affected calf was found. There is heightened surveillance and restricted movement of all warm-blooded animals from the area. Both federal and Texas state animal health teams are active in the region.
Efforts to control the screwworm rely on releasing millions of sterile flies. This method involves sterile male flies mating with wild females, effectively reducing the screwworm population.
Currently, only one facility in Panama manufactures these sterile flies, producing around 100 million each week. The U.S. Army Corps of Engineers is constructing a new facility in Edinburg, Texas, with an estimated cost of $750 million. It is projected to start producing 100 million sterile flies weekly by late 2027, scaling up to 300 million subsequently.
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