The US has a new center in Texas to disperse sterile screwworm flies to block a parasite it spawns

U.S. Opens First Domestic Sterile Screwworm Fly Facility in Decades to Protect Cattle Industry

A new center for dispersing sterile screwworm flies opened Monday in Edinburg, Texas, marking the first such facility on U.S. soil in decades. The center represents a critical defense against the flesh-eating parasite that threatens to cross the Mexican border and potentially devastate the American cattle industry.

U.S. Agriculture Secretary Brooke Rollins and Texas Governor Greg Abbott unveiled the facility, located at a former Air Force base. The center will enable the dispersal of millions of sterile male New World screwworm flies—bred in either Mexico or Panama—along both sides of the U.S.-Mexico border.

“It’s a real testament to the all hands on deck—federal, state and local—the fact that we do not have the pest in our country yet,” Rollins said during the opening ceremony.

The new facility serves as an interim solution while the USDA constructs a larger, more permanent breeding operation. The department is investing $750 million in a fly factory in the same region, though construction isn’t expected to be completed until late 2027. Additionally, the USDA is allocating $21 million to convert an existing fruit fly breeding facility in southern Mexico into one that can produce screwworm flies beginning this summer.

The sterile fly strategy employs a simple but effective biological control mechanism. When sterile male flies mate with wild females—who only mate once during their brief adult lives—the eggs laid in open wounds or on mucous membranes fail to hatch into the destructive maggots that devour the living flesh of infected animals.

These flesh-eating larvae pose a serious threat to livestock, wild mammals, pets, and potentially humans, making the control program essential for agricultural biosecurity.

The Mexican cattle industry has already suffered significant losses from screwworm infestations. In response, the United States closed its border to imports of cattle, bison, and horses from Mexico last July, disrupting an important trade relationship between the two countries.

Governor Abbott emphasized the urgency behind the new facility: “We knew we needed a short-term, gap-filling solution, which is exactly what we are cutting a ribbon on today.”

This isn’t the first time the U.S. has battled screwworm flies. A similar program breeding sterile males had largely eradicated the pest from American territory by the early 1970s. Since then, outbreaks have been rare and contained, including a limited incident in the Florida Keys in 2017 and a recent case involving a horse being imported from Argentina into Florida, which was promptly treated.

After eliminating the pest domestically, the U.S. had shuttered its fly factories. For years, a single facility in Panama has been the Western Hemisphere’s only producer of sterile males, with a capacity of about 117 million flies weekly. The planned new Texas facility will significantly expand this capacity, designed to produce up to 300 million sterile flies per week.

In November, the USDA opened a dispersal facility in Tampico, central Mexico, to distribute Panama-bred flies. However, that location sits approximately 330 miles south of the U.S.-Mexico border, limiting its effectiveness for protecting U.S. territory.

Beyond the new facilities, the USDA announced last month it would offer up to $100 million in grants for innovative projects aimed at improving fly breeding techniques, developing more effective traps and lures, and creating new treatments for infestations.

The comprehensive approach highlights the serious threat screwworm poses to American agriculture and the significant resources being deployed to prevent its reestablishment in the United States, protecting both the economic interests of the cattle industry and animal welfare across the region.