Mexico's Screwworm Fly Plant Smells of Rotting Meat, and the Town Wants It Gone

The complaint is not about the science. It is about the air.

On Thursday, residents of Metapa de Dominguez, a town in Mexico's southern Chiapas state, took to the streets to demand the removal of the sterile-fly plant that the United States and Mexico built as the centerpiece of their joint campaign against New World screwworm. The smell coming off the facility, they told Reuters, is like rotting meat and spoiled food — pungent enough to cause nausea. What used to stay near the plant's walls now drifts across town when the wind turns, and it has reached schools near the fence line, disrupting classes.

"We don't care about the investment they made. What we want is for this plant to leave here, because the smell coming over the town is too much," said Mercedes Becerra de la Cruz, a truck driver, according to the wire service.

The timing is awkward for both governments. Mexican President Claudia Sheinbaum and U.S. Agriculture Secretary Brooke Rollins inaugurated the facility on June 27, less than four months ago. Washington put $21 million into the $51 million plant, which is expected eventually to produce 100 million sterile flies a week.

Inside, flies are bred by the million, their larvae fed a formulated mix of egg, milk and powdered hemoglobin that mimics the nutrient-rich conditions of a wound. Males are sterilized before release, then fly out to mate with wild females that produce no offspring. The technique is what pushed screwworm out of the United States in the 1960s, and Metapa now sits close to the top of the supply chain that is trying to do it again.

That is where Texas enters the story. The fly — whose larvae burrow into the living flesh of cattle and other warm-blooded animals and can kill an untreated animal — has moved north out of Central America through Mexico, prompting Washington to keep a ban on Mexican cattle imports in place for more than a year. Reuters put Mexico's outbreak at nearly 48,000 cases and the U.S. total at 53. The USDA APHIS public case list has carried 54 confirmed records, all but two of them in Texas.

The northern end of that campaign runs on flies, and until the United States builds its own capacity, a large share of them are flown in from Metapa and from a facility in Panama. The USDA's new plant at Moore Air Base in Edinburg, Hidalgo County, is scheduled for completion in April 2027, with production ramping to 100 million flies a week in a first phase and 300 million once a second phase is finished. That is more than a year of dependence on a plant whose neighbors are now organized.

"We need the federal government to respond and have the plant relocated. It is far too close, right in the middle of the town," said Rosalba Merida Herrera, 49, a homemaker, in the same report. "For the sake of our children and our elderly, we are asking them to look at the situation, as this issue is now affecting the entire town."

A spokesperson for Mexico's Agriculture Ministry did not immediately respond to a request for comment.

The underlying problem is siting, and it is not unique to Chiapas. Rearing insects at industrial scale means rearing what they eat, and the byproduct is odor that a buffer zone would normally absorb. Build the plant inside a town's footprint and the buffer disappears. The technical case for sterile insect technique — a method with no chemical residue and a decades-long record against this specific pest — does not answer a resident who cannot open a window.

For Texas ranchers, veterinarians and hunters in the affected counties, nothing about the reporting routine changes this week. Suspect wounds get inspected, not treated quietly, and cases go to the Texas Animal Health Commission at 800-550-8242, the same line that has been in place since June.

But it is worth noticing what happened in Metapa. An eradication program that depends on one production site also depends on that site's neighbors, and four months in, they are asking it to leave.