Arizona-Sonora Border Reopens Cattle Trade After Screwworm
The Douglas-Agua Prieta border crossing between Arizona and Sonora, Mexico, is set to become the first U.S.-Mexico port of entry to reopen to cattle shipments after a more than yearlong closure triggered by an outbreak of the New World screwworm parasite. According to KJZZ/NPR, the reopening is scheduled for August 24, 2026, marking a significant step toward normalizing agricultural trade between the two countries.
Background: A Parasitic Crisis
New World screwworm (Cochliomyia hominivorax) is a parasitic fly whose larvae feed on the living flesh of warm-blooded animals, causing severe tissue damage and potentially death if left untreated. The female fly lays eggs in wounds or mucous membranes, and the hatched maggots burrow into the tissue. While the parasite primarily affects livestock, it can also infect pets and, rarely, humans.
The United States successfully eradicated New World screwworm in the 1960s using the Sterile Insect Technique (SIT), a method in which sterilized male flies are released to mate with wild females, producing no offspring. However, the current outbreak represents a re-emergence of the parasite in North America after decades of successful control.
The outbreak was first detected in Mexico in November 2024 and has since spread to 29 of Mexico’s 32 states. In response, the U.S.-Mexico border ports were closed to cattle imports in May 2025. The first confirmed case in the United States occurred in early June 2026 in Texas. As of late July, the parasite had spread to more than 40 animals in Texas, with additional cases reported in southeastern New Mexico.
The Reopening Plan
The U.S. Department of Agriculture (USDA) announced a phased reopening plan for southern ports on July 24, selecting the Douglas-Agua Prieta crossing as the first to resume livestock trade. As Capital Press reported, the USDA cited the crossing’s low-risk profile: no screwworm has been detected within 325 miles of the port, and the bordering Mexican state of Sonora maintains robust animal inspection programs.
Sonora has reported zero cases of the parasite, making it one of two Mexican states — along with neighboring Chihuahua — that the USDA considers the lowest risk for New World screwworm due to their geographic distance from southern Mexico, where the bulk of the country’s cases have been concentrated.
Arizona’s Enhanced Screening Protocols
Arizona has implemented new protocols to ensure the safe importation of livestock. The Arizona Department of Agriculture (AZDA) issued Director’s Administrative Order 26-04, establishing heightened screening, tracking, and inspection requirements. Notably, cattle crossing into Arizona will be monitored using electronic identification methods rather than traditional ear tags, which were found to cause trauma to ear tissue and increase the risk of screwworm infestation.
Arizona Governor Katie Hobbs expressed confidence in the state’s preparedness, stating: “Arizona has consistently demonstrated its readiness to confront the challenges of screwworm, taking swift action to safeguard our cattle industry and ranchers from this latest outbreak.”
Arizona Department of Agriculture Director Paul Brierley echoed this sentiment, emphasizing the collaborative effort behind the reopening. “We have worked tirelessly with USDA, the cattle industry, our sister states and Mexico to assure a safe border opening when the time came,” Brierley said. “Sonora is known for their excellent disease protocols, and we have implemented new requirements to assure the safe importation of livestock.”
Bilateral Cooperation and Control Efforts
Mexican President Claudia Sheinbaum highlighted the cooperative nature of the response at a press conference, characterizing it as “good coordination and good collaboration between both governments.”
The United States and Mexico have jointly retrofitted a facility in southern Mexico that began producing sterile New World screwworm flies this summer. It becomes one of two facilities producing sterile flies for the region, which are dispersed throughout the region to reduce and prevent outbreaks. Experts consider the sterile fly dispersal method the most effective strategy for combatting the parasite.
Economic Implications
The reopening comes at a critical time for the livestock industry. The U.S. cattle herd is at historically low levels, making the industry particularly vulnerable to additional disruptions. Beef prices have been elevated, and the border closure had severely impacted ranchers on both sides of the border. Sonora is a major cattle-producing state in Mexico, and the Douglas-Agua Prieta crossing is a key trade corridor for livestock between Sonora and Arizona.
The National Cattlemen’s Beef Association and the Meat Institute have supported the reopening, while some critics, including R-CALF CEO Bill Bullard, have argued that the border should remain closed until the U.S. ramps up sterile fly production and Mexico stops the illegal movement of cattle.
What’s Next
Additional ports in Santa Teresa and Columbus, New Mexico, could reopen later depending on progress under the Joint Action Plan between the U.S. and Mexico. The success of the Douglas pilot reopening will inform decisions about other crossings. Continued monitoring of screwworm cases in Texas and New Mexico will be critical as authorities work to prevent further spread of the parasite while restoring normal agricultural trade. The sterile fly production facility is a positive development but requires sustained investment to achieve the capacity needed for long-term control.