USDA Confirms First Texas Screwworm Case Since 1966

The domestic confirmation of the New World screwworm in Texas escalates a critical agricultural emergency that has already disrupted highly integrated North American livestock supply chains. Following the United States' complete import ban on live Mexican livestock, northern Mexico's ranching export corridors face significant economic losses alongside stringent domestic movement controls enforced by SADER and SENASICA. To mitigate broader commercial volatility, both nations have intensified binational technical cooperation, accelerating multi-million-dollar biological containment infrastructure to suppress regional pest populations and establish a framework for a phased reopening of the border.

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The US Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed the detection of the New World screwworm (NWS) in a bovine in Zavala County, Texas. The case marks the first domestic detection following a year of advanced surveillance and cross-border containment efforts in Mexico and Central America designed to delay the parasite's entry into the United States.

The infestation was identified in the umbilical area of a 3-week-old calf. To date, no further detections have been reported. The NWS is a destructive pest that infests livestock, wildlife, pets, and occasionally humans by entering through open wounds or body openings to feed on living flesh.

In response to the detection, the USDA and Texas officials established a unified Incident Command Team with the Texas Animal Health Commission to deploy response personnel and execute containment protocols. Authorities implemented a 20km infested zone around the site, introducing strict quarantines, animal movement controls, and localized surveillance.

Eradication efforts include the expedited release of sterile NWS flies, a technique previously utilized to eliminate the pest domestically. Ground release chambers are being deployed to supplement the 4 million sterile flies already being released aerially in the region each week. Additionally, officials are increasing fly trapping along the border, initiating wildlife surveillance, and preparing resources from the National Veterinary Stockpile, including treatments and logistical equipment. "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, Under Secretary for Marketing and Regulatory Programs. Hoskins noted that federal models had projected the parasite entering the country in 2025, but coordinated efforts with industry and state partners extended the timeline for domestic preparedness.

The USDA confirmed that the commercial food supply remains safe, as screwworms do not infest processed meat or agricultural products. The Food Safety and Inspection Service (FSIS) continues to mandate inspections of all eligible animal species under the Federal Meat Inspection Act, ensuring any infested livestock is intercepted before entering the food supply. To minimize broader economic impacts, the USDA is collaborating with animal health officials and international trading partners to regionalize live-animal trade restrictions to defined geographic areas rather than executing nationwide bans.

Bilateral Containment Context and North American Trade Impacts
MBN has reported that the re-emergence of the NWS  in Mexico, which initially triggered the National Animal Health Emergency Protocol in July 2024, fundamentally altered the bilateral agricultural landscape. Following a continuous spread through southern and central Mexican states, the United States halted all imports of live Mexican livestock, including cattle, horses, and bison. This border closure significantly disrupted highly integrated North American supply chains. For northern Mexico's livestock sector, which previously exported thousands of cattle daily through states like Sonora and Chihuahua, the restrictions resulted in an estimated daily loss of US$11.4 million in foreign revenue. 

In response to the trade restrictions and the northward advance of the pest, Mexico’s Ministry of Agriculture and Rural Development (SADER) and the National Service for Agrifood Health, Safety, and Quality (SENASICA) deployed an extensive operational containment strategy. This included the activation of a 10-week regional suppression pilot plan across highly impacted polygons in Yucatan, alongside strict movement controls enforced via Internal Verification and Inspection Points (PVI), Itinerant Routes, and localized checkpoints. Furthermore, Mexican authorities implemented targeted technical sanitary protocols, such as distributing over 120,000 wound treatment kits and establishing strict quarantine circles stretching 20km to 40km around any newly detected cases.  

To counter the economic threat, Mexico and the United States have intensified binational technical cooperation, heavily relying on the expansion of biological control via the Sterile Insect Technique (SIT). While the USDA currently produces 100 million sterile flies per week at the operational COPEG facility in Panama, regional demand has required a massive infrastructure scale-up. To expand this capacity, the USDA has invested US$21 million to renovate a production facility in Metapa, Mexico. This site is expected to produce an additional 60 million to 100 million sterile flies per week once production begins in summer 2026, as reported by MBN. Together with a future plant in Texas, these facilities aim to eventually provide a total regional output of 500 million flies per week.

To complement these massive production efforts, a highly integrated network of cross-border dispersal facilities has already been rendered operational. In April 2025, APHIS and SENASICA partnered to establish a permanent dispersal facility in Tuxtla Gutiérrez, Chiapas, capable of distributing 100 million flies per week. This was strategically followed in November 2025 by the opening of a dispersal facility in Tampico, Mexico, to facilitate targeted aerial releases across northeastern Mexico to slow the pest's northward migration. 

Additionally, construction is complete on a critical dispersal facility at Moore Air Base in Texas, which is now fully operational and capable of dispersing 100 million flies per week along the US-Mexico border. Recent diplomatic and agricultural summits between the two nations continue to evaluate these technical indicators to establish a phased, gradual reopening of the border to Mexican cattle exports.