Mexico’s major initiative to eradicate the screwworm will be ready in July 2026

In 1991, the Mexican state of Chiapas was the epicenter of the first eradication of the cattle screwworm infestation in history. An old sterile fly plant, which operated for about seven years in Chiapa de Corzo — about nine miles from the capital, Tuxtla Gutiérrez — once produced millions of flies that achieved that initial victory over the pest. Now, 34 years later, the same disease is causing alarm in North and Central America.

The Mexican government is preparing a major response to this problem. The Ministry of Agriculture and the United States government are converting a 14-hectare complex in the Chiapas municipality of Metapa de Domínguez into the most modern facility in the world: Moscamed, as the factory is called, will begin manufacturing 100 million sterile flies by July 2026.

Until now, the sterile flies that are spread throughout the country to combat the screwworm plague (100 million each week) are brought from a plant managed by the Panama-United States Commission for the Eradication and Prevention of the Cattle Screwworm (Copeg), in Panama, where they have been working at maximum capacity to control the pest since January 2025. Copeg is, for now, the only plant that manufactures sterile flies of the species Cochliomya hominivorax, more commonly known as screwworm fly, and whose larvae are responsible for causing myiasis disease in warm-blooded species, including humans.

The sterile insect technique is a form of birth control for the population; it tries to prevent more insects from being born

Geneticist Salvor Meza

On the Chiapas side, in the large Metapa de Domínguez complex—located just over a mile from the border with Guatemala and about 19 miles from the city of Tapachula—a large scientific and technical community made up of geneticists, agronomists, veterinarians, and other professionals work every day to manufacture millions of sterile Mediterranean flies, a species that damages more than 250 types of fruits and vegetables, a plague that Mexico is so far free of, although if it were to reach national territory it would be a commercial and food catastrophe.

This complex was inaugurated in 1979 with funding from the International Atomic Energy Agency (IAEA), and for more than 40 years it was an international benchmark in the fight against one of the 10 pests considered the most lethal in the world: the Mediterranean fruit fly (Ceratitis capitata). In 2021, the Mexican government built a new plant there, arguing that it was still necessary to “protect national fruit and vegetable production, which includes more than 250 plant species” and was valued at $19 billion in 2024 in domestic consumption and exports, according to official data.

Human, economic, and governmental efforts around the facility, called Moscamed, have had to be reoriented since the screwworm myiasis disease re-emerged in Costa Rica in July 2023 and spread rapidly northward.

Two years later, in July 2025, Mexican Secretary of Agriculture Julio Berdegué inaugurated work on the conversion of part of the Moscamed complex. This building, 28% of which was completed as of October, has been completely dismantled and emptied. In a few months, it will become Panama’s replacement for the production of sterile screwworm flies on national soil.

Although it is still in its infancy, authorities from the National Service of Health, Safety and Agri-Food Quality (Senasica) are optimistic and estimate that by July 2026 this space where sterile Mediterranean flies were formerly manufactured will be fully operational for the production of the screwworm species.

Hunberto Gomes Velasques, Moscamed program coordinator, explained: “An analysis was made according to the viability of this property for the production of sterile screwworm flies and we found three advantages: one of them is that this property has a BSL-2 laboratory [of 4 that exist] and has 2,016 square meters of biocontainment area, which means that it is restricted for the entry and exit of materials, and we also have a Cobalt 60 irradiator that, with certain adjustments, can be adapted to [the new] production.”

Moscamed opens the door

It’s early morning and at Tapachula International Airport, several small planes belonging to Servicios Mubarqui S. de R.L. de C.V. are preparing to receive the cargo from the Moscamed packing facility in the same city. The flies have arrived in metal containers and will be dropped from the sky. For several hours, the flies have been kept in cooling rooms at temperatures between 0 and 3 degrees Celsius, which keeps them dormant or lethargic until they are loaded onto the aircraft.

Twice a week, these small planes release sterile flies, in flights typically lasting an average of four hours — there are 3.6 million flies per flight — in so-called release zones, the areas of the country where the pest is present: Chiapas, Oaxaca, Veracruz, parts of Guerrero, and, most recently, Querétaro.

José Luis Quintero Fong, coordinator of the Moscamed operational program, recalls that the first eradication of the screwworm pest in the country took almost two decades. He adds: “We hope the screwworm fly pest will be eradicated from Mexico in less than 19 years. We are working toward that goal, and we hope we can do it in a much shorter timeframe. [...] This will be possible if we spread the word. The more we know about the pest, the more informed we are, the easier it will be to prevent its spread.”

By the time they are released, the Mediterranean flies—whose eggs are provided by another program facility, El Pino, located in Guatemala — are already sterile and have gone through complex processes in Metapa. These include incubation, feeding, growth, larvae collection, feeding, dyeing — to differentiate them from wild flies—and irradiation with Cobalt 60, the technique that nullifies their reproductive capacity.

The sterile insect creation process, which lasts about 21 days, takes place in this gigantic complex where dozens of interconnected buildings house the long, tall rooms acclimatized to different temperatures to accommodate each life stage of the insect.

Geneticist Salvor Meza explains: “Our production is focused on creating a biological barrier to prevent insects from entering the country. The sterile insect technique is a form of birth control for the population; it tries to prevent more insects from being born. It is environmentally friendly, completely ecological, and avoids the use of thousands of liters of pesticide; this is the function of this plant.” All the processes that take place at Moscamed, although currently monopolized for sterile Mediterranean flies, will be carried out in very similar ways for the production of screwworm flies in a few months.

The project to convert this new, exclusive space for the screwworm fly is backed by a joint investment between Mexico and the United States of $51 million, of which the Mexican government contributes $30 million and the United States $21 million. The goal is to strengthen the control and eradication strategy, which began in mid-2024. According to Quintero Fong, the new plant in Metapa is expected to start with a production of between 30 and 60 million sterile flies per week, a figure that will increase to reach 100 million additional insects to those manufactured by Copeg.

With the other leg of the project, the construction of a manufacturing plant for these flies in Texas, international efforts project a production of up to 500 million flies per week, which will be released throughout the region. If international cooperation continues, myiasis could be eradicated in less time than the first time. Some representatives of Senasica have even talked about achieving this goal in five years.

The crisis in numbers

Information from Senasica indicates that cases of myiasis caused by the screwworm in Mexico have decreased by 28% compared to September 11, when the incidence peaked. The agency’s most recent data indicates a total of 7,943 positive cases recorded in Mexico, representing 0.02% of the national livestock herd.

From November 2024 to August 31, 2025, the cost of the health deployment to combat the screwworm amounted to 1.128 billion pesos, more than $60.34 million. Furthermore, Senasica estimates that 700,880 head of live cattle have not been exported to the United States as a result of the disease. The lost exports — due to the closure of the northern border — represent $642 million. The impact on cattle ranchers from selling in the Mexican market instead of exporting is estimated at $103.4 million (approximately 2,022.50 million pesos).

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