The U.S. Department of Agriculture (USDA) announced on Monday a phased reopening of livestock import sites along the Mexican border, beginning July 7 with Douglas, Arizona.
Agriculture Secretary Brooke L. Rollins said the decision follows weeks of intensive collaboration with Mexican authorities to combat New World Screwworm (NWS), a devastating livestock parasite that prompted the closure of all southern border ports on May 11.
Why It Matters
The extended livestock port shutdown disrupted a critical trade relationship between the U.S. and Mexico, affecting ranchers and livestock operations on both sides of the border. NWS poses an existential threat to American agriculture—the parasitic fly lays eggs in open wounds of livestock, producing maggots that burrow into living flesh, causing severe injury and often death.
The USDA successfully eradicated NWS from the United States in 1966, but its return would devastate the livestock industry and threaten food security.
The economic stakes are substantial. A similar outbreak in Florida in 2016 required euthanizing 102 infected animals, demonstrating the pest’s destructive potential even in contained situations. The current threat represents the parasite’s northward march through Central America over two years, reaching Mexico in November 2024 and spreading to within 700 miles of the U.S. border.
NWS has systematically moved through Panama, Costa Rica, Nicaragua, Honduras, Guatemala, El Salvador, Belize and now Mexico, with cases detected in Oaxaca and Veracruz states.
What To Know
The reopenings span three months, with five ports gradually resuming operations. The other four are:
- Columbus, New Mexico, on July 14
- Santa Teresa, New Mexico, on July 21
- Del Rio, Texas, on August 18
- Laredo, Texas, on September 15
Each reopening will be evaluated for adverse effects before proceeding to the next phase. The parasite’s rapid spread through Mexico triggered the May suspension after the USDA’s February attempt to resume imports with enhanced inspection protocols proved insufficient.
The department’s response included deploying sterile fly dispersal operations, releasing over 100 million sterile flies weekly to disrupt the pest’s reproductive cycle. This sterile male technique, previously explained to Newsweek by Texas A&M Professor Phillip Kaufman, works because female screwworm flies mate only once—flooding areas with sterile males prevents successful reproduction. Five Animal and Plant Health Inspection Service teams conducted comprehensive on-site assessments in Mexico this month to evaluate containment efforts.
Strict import protocols now govern the reopening. Only cattle and bison born and raised in Sonora or Chihuahua, or those treated according to specific NWS protocols, qualify for import initially. Texas ports won’t reopen until Coahuila and Nuevo Leon adopt similar protocols. Equines from anywhere in Mexico can be imported but require a seven-day quarantine and compliance with equine NWS protocols.
Mexico is renovating its sterile fruit fly facility in Metapa, expected to produce 60 million to 100 million sterile flies weekly by July 2026. This represents progress toward the long-term goal of producing 400 million to 500 million flies weekly to reestablish the NWS barrier at the Darién Gap.
What People Are Saying
Rollins, in a Monday statement: “At USDA we are focused on fighting the New World Screwworm’s advancement in Mexico. These quick actions by the Trump Administration have improved the conditions to allow the phased reopening of select ports on the Southern Border to livestock trade. We are continuing our posture of increased vigilance and will not rest until we are sure this devastating pest will not harm American ranchers.”
Speaking previously to Newsweek, Kaufman, also head of the department of entomology at Texas A&M University, said: “To eliminate the fly, especially under a more widespread infestation, requires several complimentary approaches, including monitoring for infested wounds for larvae, using fly-specific traps, and the mass release of sterile males.”
He added: “The sterile male technique is crucial in this process as the female screwworm fly mates only once and by inundating the infested area with sterile males we in effect make the females lay eggs that do not hatch. As these wild females die out, the population drops, and the fly is ultimately eliminated. This takes time to accomplish but has been proven effective repeatedly.”
What Happens Next
The USDA will continuously monitor each port reopening for adverse effects before proceeding to the next phase.
Officials reported no notable increase in NWS cases or northward movement over the past eight weeks, indicating progress in containment efforts. Additional improvements in Mexico’s animal movement controls and surveillance efforts remain critical for remaining ports to reopen as scheduled.
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