US-Mexico cattle trade set to resume amid persistent screwworm fears

The United States is set to partially lift a ban on Mexican cattle imports on Monday, marking the first easing of restrictions imposed over a year ago to prevent the spread of the flesh-eating screwworm parasite. The phased reopening will initially allow shipments through Arizona, with additional ports in New Mexico expected to follow.

Mexican Agriculture Minister Columba Lopez announced that authorities will intensify the dispersal of sterile flies in the northern border states of Sonora and Chihuahua. This technique, which involves releasing sterilized flies to mate with wild females and produce no offspring, is a key strategy in eradicating the pest.

The decision to resume trade has drawn criticism from some US cattle groups and state officials, who argue that the parasite continues to spread in northern Mexico and has already been detected in Texas and New Mexico. The US Department of Agriculture (USDA) has stated that the reopening will be phased and contingent on Mexico's compliance with screwworm-control measures.

Chihuahua, a major cattle-exporting state, has reported 183 confirmed screwworm cases since its first detection in July. Neighboring Sonora has confirmed two cases after announcing its first detection last week and has activated emergency surveillance and containment protocols.

Mexico recently opened a sterile-fly production plant in Chiapas, while the US is constructing its own facility in Texas, expected to be completed by spring 2027. Mexican President Claudia Sheinbaum defended the sterile fly technique as a "modern" and "effective" method to combat screwworm, stating that it "allows us to open the border."