New Detections in Two Texas Counties
Federal agriculture officials confirmed three additional New World screwworm cases in Texas on Sunday, bringing the total number of U.S. infections to 15 since the pest was first detected domestically earlier this month. The cases represent the first screwworm infestation on American soil in six decades.
Within a 24-hour window, one lamb tested positive in Crockett County and two calves tested positive in Edwards County. Those detections follow the initial confirmed case on June 4, when a calf near Crystal City, Texas, tested positive — marking the first domestic screwworm finding since the parasite was eradicated from the United States in the 1960s.
The New World screwworm is a parasitic fly whose larvae burrow into the living tissue of warm-blooded animals, creating severe wounds that can prove fatal if left untreated. Texas ranchers had watched the pest steadily advance northward through Mexico over the past year, anticipating it would eventually cross the border.
USDA Deploying Sterile Fly Strategy
The U.S. Department of Agriculture is responding with what officials describe as aggressive eradication measures, including the dispersal of tens of millions of sterile flies over affected areas. The sterile insect technique works by flooding a population with non-reproducing males, gradually collapsing the pest’s ability to sustain itself.
To support long-term containment, the USDA broke ground in April on a dedicated facility to mass-produce sterile flies. That facility is not expected to be operational until late 2027, leaving officials reliant on existing production capacity in the interim.
The economic stakes are significant. Analysts have projected that a widespread screwworm outbreak across Texas could cause as much as $1.8 billion in economic damage to the state’s livestock industry. Texas cattle ranching is among the largest agricultural sectors in the country, and any sustained infestation would carry ripple effects through beef supply chains that reach Idaho and other western states.
For Idaho cattle and sheep producers, the development is worth monitoring closely. While no cases have been detected outside Texas, the pest’s rapid spread from Mexico to multiple Texas counties within weeks underscores the threat it poses to livestock operations throughout the West. Idaho’s agricultural sector is already under pressure from water supply reductions along the Snake River, and a screwworm spread northward would compound challenges for ranchers already managing difficult conditions.
What Comes Next
The USDA is expected to continue sterile fly dispersal efforts across affected Texas counties while monitoring for any spread beyond the current detection zone. Livestock producers in neighboring states are advised to inspect animals regularly for unusual wounds or signs of fly strike. With the sterile fly production facility still more than a year from coming online, containment in the near term will depend entirely on existing eradication tools and rancher vigilance. Federal officials have not yet indicated whether additional counties or states have been placed under heightened surveillance protocols.