The easing marks the first crack in a U.S. ban imposed more than a year ago to block New World screwworm, a parasite whose larvae feed on the open wounds of livestock and, occasionally, humans. Shipments are initially moving through Arizona, with additional New Mexico ports scheduled to open as the rollout expands. The USDA reported 46 screwworm cases identified in Texas and New Mexico, with two still active.
Why the Ban Started and Why It Is Lifting Now
The original suspension halted a trade pipeline that historically moves hundreds of thousands of feeder cattle northward each year, supplying feedlots across the Southwest and underpinning beef supply chains in both countries. Mexican ranchers bore the brunt of the shutdown, forced to hold animals longer at added cost, while U.S. feeders scrambled to replace lost inventory.
Resumption comes as Mexico intensifies screwworm containment in its northern border states, where recent detections prompted heightened scrutiny of livestock exports. Mexican authorities have leaned on the sterile-insect technique, releasing irradiated male flies that mate with wild females and produce no offspring, gradually collapsing local populations.
Sterile Fly Production Ramps Up
Mexico’s Chiapas facility is now producing sterile flies, a critical tool in the decades-old eradication playbook. A dedicated U.S. sterile-fly plant is slated to come online by spring of 2027, giving American agriculture its own domestic production capacity rather than relying entirely on Mexican output.
That timeline matters. Sterile-insect release is effective but slow, requiring sustained weekly drops over vast territory. Any gap in production or logistics can allow wild populations to rebound, particularly in warm, humid regions where the pest thrives year-round.
Critics Question the Phased Reopening
The plan has drawn criticism from ranchers and veterinary experts who argue that two active domestic cases, plus the broader 46-case count across Texas and New Mexico, suggest the threat has not been fully extinguished. Some industry voices want tighter pre-shipment inspection protocols, mandatory quarantine periods, and broader surveillance funding before ports beyond Arizona are cleared.
USDA officials have defended the phased approach as risk-based, allowing trade to restart where surveillance and containment are strongest while keeping pressure on areas where the pest persists. The agency has not publicly detailed the specific thresholds that would trigger additional port openings or a renewed suspension.
What Happens Next
Watch the New Mexico port expansion closely. If case counts in Texas and New Mexico stay flat or decline through the fall, the reopening will likely accelerate and restore a significant share of normal Mexican cattle imports. A spike, however, could force USDA to pause or reverse course, repeating the supply-chain whiplash of the past year.
The 2027 sterile-fly plant in the United States will be the longer-term bellwether. Until domestic production capacity exists, the entire containment strategy hinges on Mexican facilities in Chiapas and the political stability of cross-border cooperation. For now, the border is open, but the screwworm is not gone, and every shipment moving north carries the weight of that unresolved tension.
— Isabella Morales, food desk, AXO News