Cross-border cattle trade between the United States and Mexico resumed on Monday under a phased reopening plan, even as Mexico increases efforts to contain the spread of screwworm in its northern states. The U.S. Department of Agriculture (USDA) reopened the port of Douglas, Arizona, to Mexican cattle imports, marking the first easing of a ban that has been in place for more than a year.
The trade suspension was originally implemented to prevent the New World screwworm, a parasite that feeds on the flesh of living animals, from entering the United States. While the reopening has begun, the parasite has recently been detected in the Mexican states of Chihuahua and Sonora, as well as in the U.S. states of Texas and New Mexico. Mexican authorities reported that Chihuahua has seen 183 confirmed cases since July, while Sonora has confirmed two cases.
To manage the outbreak, Mexican Agriculture Minister Columba Lopez announced the reinforced dispersal of sterile flies in northern border regions. This technique involves releasing sterilized male flies that mate with wild females but produce no offspring, eventually reducing the population. Mexico recently opened a production facility for these flies in Chiapas, and the U.S. is currently constructing a similar plant in Texas, which the USDA expects to complete by the spring of 2027.
The scale of the trade involves thousands of animals moving through specific border ports. Initially, the reopening is limited to the Douglas, Arizona, port, but the USDA is evaluating the future reopening of Santa Teresa and Columbus in New Mexico. The impact on a per-ranch basis would be felt through the resumption of revenue from sales that were halted during the year-long ban. However, the USDA has stated that it will pause port operations if audits or observations indicate an increased risk in Sonora or Chihuahua.
The knock-on effects extend to the North American agricultural supply chain and long-term biosecurity policy. The reliance on sterile fly technology sets a precedent for how the two nations manage transborder biological threats. The success of this phased reopening depends on Mexico's ongoing compliance with screwworm-control measures and the completion of the U.S. sterile fly plant in 2027. What happens next includes a series of post-opening audits by the USDA and the potential expansion of import eligibility to horses and bison at additional New Mexico ports.