US, Mexico inaugurate sterile fly plant in Chiapas in cross-border screwworm fight

METAPA, Mexico June 27 - Senior Mexican and U.S. officials inaugurated a sterile fly production plant in southern Chiapas on Saturday, a milestone in efforts to contain the New World screwworm outbreak as it has spread across borders and disrupted cattle trade.

Mexican President Claudia Sheinbaum and U.S. Agriculture Secretary Brooke Rollins attended the opening of the facility in Metapa de Dominguez, near the Guatemala border. The plant, a U.S.-Mexico project costing over $50 million, will eventually produce up to 100 million sterile flies weekly to suppress the wild screwworm population.

The parasite burrows into the flesh of warm-blooded animals and can be fatal if untreated.

Even with the new capacity, experts have said the total supply of sterile flies will fall short of what is needed to eradicate the pest.

The facility's launch comes more than 18 months after Mexico confirmed its first screwworm case in November 2024. The outbreak then advanced northward through Mexico and eventually into the U.S., where the first cases in decades were confirmed in early June in Texas. Those cases have heightened concerns about the risk to the U.S. cattle industry.

"Our countries have beaten this before, 40, 50 years ago. We will beat the New World screwworm again sooner than anyone would have thought because of the extraordinary work that is going to happen at this facility," Rollins said.

WARNINGS SINCE 2023

Despite warnings dating back to 2023 by the Panama-United States Commission for the Eradication and Prevention of Screwworm (COPEG) that screwworm was moving northward, officials struggled to contain the spread. The parasite has since infected more than 30,000 animals in Mexico. Neither Mexico nor the U.S., which is building its own sterile fly facility in Texas, announced plans for these plants until 2025.

In response to the outbreak, the U.S. has kept its border mostly closed to Mexican live cattle since May 2025, disrupting a trade that previously supplied more than 1 million animals annually to U.S. feedlots. The move has squeezed supply in Texas, leaving some feedlots with empty pens and contributing to historically tight cattle inventories.

The disruption has also driven a shift in Mexico. Ranchers who once exported live cattle north have increasingly opted to fatten and process animals domestically, investing in feedlots and slaughter capacity. With fewer live exports, Mexican beef shipments to the U.S. surged in 2026.

"Animal diseases, pests and the challenges of food safety aren't limited by borders," Sheinbaum said. "In the face of those challenges, the best response is to team up, share our experiences and build solutions together."

The new sterile fly plant is expected to double the number of insects available for release beyond what COPEG's plant in Panama produces. That plant has been operating at capacity with about 100 million flies per week. Those sterile flies have most recently been released along the U.S.-Mexico border near Texas.

(Reporting by Cassandra Garrison in Mexico CityEditing by Rod Nickel)

Copyright Reuters or USA Today Network via Reuters Connect.

This story was originally published June 27, 2026 at 6:15 PM.