Sonora Activates Emergency Protocols Over Screwworm Case

The detection of New World screwworm in Sonora has triggered emergency sanitary containment protocols and biosecurity measures across North American livestock corridors. With northern Mexican ranching states facing daily revenue losses of US$11.4 million due to cross-border live cattle trade suspensions, binational agencies are scaling sterile insect technique production to 500 million flies per week. The resurgence directly impacts cattle ranchers, meat processors, veterinary health authorities, and international agricultural supply chains navigating USMCA sanitary regulations.

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The Mexican state of Sonora activated emergency animal health protocols for surveillance, containment, and control following the confirmation of its first case of New World screwworm (NWS). Sonora Governor Alfonso Durazo announced the containment measures to safeguard the northern state's biosecurity status and prevent the parasitic fly from spreading into commercial cattle herds. "We reinforced the sanitary perimeter and actions in the area to prevent its dispersion and protect the sanitary status of our state," Durazo stated.

The emergency response in Sonora follows the re-emergence of the parasitic pest in Mexico, which initially triggered the National Animal Health Emergency Protocol in July 2024. The pest feeds on the living tissue of warm-blooded animals by entering through open wounds or body openings, posing a direct threat to livestock productivity, animal welfare, and wildlife populations. 

US Cases Signal Northward Advance

On June 3, 2026, the US Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed the detection of New World screwworm in a three-week-old calf in Zavala County, Texas. The case marked the first domestic detection in the United States following a year of surveillance and cross-border containment efforts in Mexico and Central America. Larvae were identified in the umbilical area of the calf.

In response to the Texas detection, the USDA and the Texas Animal Health Commission established a unified Incident Command Team to deploy response personnel and execute containment protocols. Authorities implemented a 20-kilometer infested zone around the site, introducing strict quarantines, animal movement controls, and localized surveillance. Eradication measures include ground release chambers supplementing the four million sterile NWS flies released aerially in the region each week, fly trapping along the border, and deploying treatments from the National Veterinary Stockpile. 

"Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action," said Dudley Hoskins, USDA Under Secretary for Marketing and Regulatory Programs. Hoskins noted that federal models projected the parasite entering the United States in 2025, but coordinated efforts extended the timeline for domestic preparedness.

Subsequent surveillance confirmed additional infections in the United States, including three calves and one goat in Texas, as well as a dog in Lea County, New Mexico. US Secretary of Agriculture Brooke Rollins testified before the US Senate that unauthorized livestock movements and illicit trafficking by Mexican criminal organizations facilitated the northward advance of the pest. 

"Tens of millions of people moving north toward the United States, bringing their livestock with them, and with the illegal trafficking of cattle by Mexican cartels, we knew this was coming," Rollins stated. However, US authorities have not disclosed evidence directly linking the confirmed Texas and New Mexico cases to cattle originating from Mexico, and investigations into the source of the infections remain ongoing.

Bilateral Containment

The northward spread of the parasite fundamentally altered the bilateral livestock trade landscape after Mexico activated its National Animal Health Emergency Protocol in July 2024. Following the continuous spread of the pest through Mexican states, the United States halted all imports of live Mexican livestock — including cattle, horses, and bison — in November 2024. For northern Mexico's livestock sector, which previously exported thousands of cattle daily through states like Sonora and Chihuahua, the border closure resulted in an estimated daily loss of US$11.4 million in foreign revenue.

To combat the outbreak, Mexico’s Ministry of Agriculture and Rural Development (SADER) and the National Service for Agrifood Health, Safety, and Quality (SENASICA) deployed extensive containment measures throughout late 2024 and early 2025, including a 10-week regional suppression pilot plan in Yucatan, Internal Verification and Inspection Points (PVI), the distribution of over 120,000 wound treatment kits, and quarantine circles stretching 20 to 40 kilometers around new detections. Meanwhile, in June 2026, a joint $1 million initiative by the International Atomic Energy Agency (IAEA) and the Food and Agriculture Organization (FAO) began deploying nuclear-based Sterile Insect Technique (SIT) applications across Central America and Mexico.

At the same time, Mexico and the United States have intensified technical cooperation to expand SIT capacity across key milestones. In May 2025, the USDA invested US$21 million to renovate a production facility in Metapa, Mexico, scheduled to begin production in summer 2026, adding 60 million to 100 million sterile flies per week alongside the 100 million flies produced weekly at the COPEG facility in Panama. 

Combined with a planned facility in Texas, total regional output is targeted at 500 million flies per week. Cross-border dispersal facilities were rendered operational in Tuxtla Gutiérrez, Chiapas, in April 2025, in Tampico, Mexico, in Nov. 2025, and at Moore Air Base in Texas in early 2026 to actively disperse sterile flies along migration corridors. 

The USDA confirmed that the commercial food supply remains safe, as the Food Safety and Inspection Service (FSIS) mandates inspections under the Federal Meat Inspection Act. As of Aug. 2026, bilateral agricultural officials continue evaluating technical indicators and containment protocols to establish a phased, gradual reopening of the border to Mexican cattle exports.