Key facts
- Panama and Mexico produce about 150 million sterile flies a week, per US and Mexican government data.
- Experts recommend 500 million sterile flies a week as the benchmark to keep the pest south of Panama.
- Mexico has recorded about 51,000 confirmed screwworm cases and the United States 120, per the report.
- USDA spokesperson Nancy McNiff said the agency has acted urgently to get more sterile flies into the field.
- A Texas plant under construction is not expected to start production until spring 2027.
- USDA awarded a $610 million contract to M.A. Mortenson to build the Texas facility, per spending records.
The United States has recorded 120 screwworm cases in cattle and still has no sterile-fly production plant of its own, more than three years after the parasite broke through a sterile-fly barrier in Panama in early 2023, according to a Reuters report published on November 9. The report, based on interviews with 15 current and former officials and experts in the US, Mexico and Panama, said efforts to scale up fly production still lag.
Panama and Mexico together produce about 150 million sterile flies a week, according to US and Mexican government data. That is less than a third of the 500 million per week used during a 1960s campaign that eradicated the screwworm in the US, and which experts recommend as the benchmark to keep the pest contained south of Panama. The US has no plant of its own, and one under construction in Texas is not expected to start production until spring 2027.
The parasite has spread across most of Mexico, with about 51,000 confirmed cases, the report said. In late February 2023, officials in Panama's Darien province confronted about 800 cases inside the jungle that had served as North America's last line of defense. In April 2023, COPEG, the US-Panamanian organization that gets most of its funding from the US, decided to increase sterile-fly production to 100 million a week from 20 million a week, a Panamanian official involved in the response said. Panama declared the spread an emergency in July 2023.
In December 2023, the administration of former US President Joe Biden announced nearly $110 million in additional funding for screwworm detection and sterile-fly production in Panama and elsewhere. Panama's plant reached 100 million flies a week in November 2024, the same month Mexico confirmed its first cases in Chiapas, the Panamanian official said. By then, authorities knew 100 million flies a week was not enough, the official told Reuters.
Elections in the United States and Mexico slowed the response, the report said. A Mexican official familiar with the response said outgoing officials in September 2024 warned their successors the epidemic needed immediate attention, and the handover delayed the effort by three to four months. In May 2025, the Trump administration announced $21 million for the Metapa project and closed the border with Mexico to cattle imports for more than 15 months, disrupting a multibillion-dollar trade. Sterile-fly drops from COPEG shifted to the Texas-Mexico border in February 2026, and the first US case was confirmed on June 3. Mexico inaugurated the Metapa plant on June 27, more than 18 months after its first case, by which time the parasite had spread across 27 states.
USDA spokesperson Nancy McNiff said in emailed responses that the agency has "acted urgently and pursued every practical avenue to get more sterile flies into the field as quickly as possible." Spokespeople for Mexican President Claudia Sheinbaum, Mexico's agriculture ministry, COPEG and Panama's government did not respond to requests for comment, Reuters said.
In March, the Trump administration awarded a $610 million contract to M.A. Mortenson to construct the Texas facility, according to publicly available records of the contract through a US government spending database. USDA initially believed the project could take up to five years, McNiff said. At a September meeting of the Texas A&M Board of Regents, Agriculture Secretary Brooke Rollins said Defense Secretary Pete Hegseth had moved the project to the top of the Army Corps' priority list, cutting the timeline to about 18 months, or fall 2027. John Bellinger, Rollins' advisor on screwworm and a member of the board, said he pushed to move even faster: "For only $250 million more, we got it moved to April 1 of next year."
Mortenson spokesperson Cameron Snyder said in an email that the company is committed to working with the USDA and the Army Corps to deliver the plant quickly. Until the plant opens, the US remains reliant on flies produced elsewhere. Although Chiapas remains Mexico's hardest-hit state with about 8,200 confirmed infestations, USDA said all sterile flies produced in Panama and Mexico are being released in northern Mexico and the US. Sonja Swiger, an entomologist at Texas A&M University, said: "We don't have enough flies. They knew that right away." Some experts estimate it could take as long as a decade to push the infestation back to Panama.