U.S. Suspends Livestock Imports from Mexico Amid Screwworm Threat
The United States has once again halted imports of live cattle, horses, and bison from Mexico, citing concerns over the re-emergence and northward spread of the New World Screwworm (NWS), a dangerous and flesh-eating parasite that can devastate livestock populations. U.S. Agriculture Secretary Brooke Rollins announced the immediate suspension, emphasizing the critical need to protect American cattle and the nation’s food supply from this potentially devastating threat.
The decision follows the detection of NWS in remote Mexican farms within 700 miles of the U.S. border, prompting the Agriculture Department to issue a statement highlighting the "unacceptable northward advancement" of the parasite. Rollins, in a social media post, underscored the severity of the situation, recalling the last NWS invasion, which took three decades for the U.S. cattle industry to recover from. She vowed to prevent a similar recurrence.
The New World Screwworm, despite its name, is actually a fly. The larvae, or maggots, of this fly are the true danger. They burrow into open wounds or openings in an animal’s skin, creating extensive tissue damage as they feed. These maggots use sharp mouth hooks to tear at the host’s tissue, causing immense pain and potentially leading to death if left untreated. The adult screwworm fly resembles a common housefly but can be distinguished by its orange eyes, metallic blue or green body, and three dark stripes along its back.
The U.S. successfully eradicated NWS in 1966 through the release of sterile male flies and pupae. This innovative approach led to infertile screwworm flies, effectively disrupting the parasite’s reproductive cycle and eliminating it from the country. However, the recent detection in Mexico has raised concerns about a potential re-infestation in the United States.
The suspension of livestock imports has sparked disagreement and frustration from Mexican officials. Luis Fernando Haro, the chief of Mexico’s agricultural council, argued that the ban is unnecessary and ineffective, claiming that established protocols already guarantee that cattle crossing into the U.S. are screwworm-free. Mexican Agriculture Secretary Julio Berdegue also expressed his disagreement with the ban but remained hopeful that the two countries could reach a resolution soon.
Rollins, however, has defended the decision, emphasizing that the protection of U.S. animals and the safety of the nation’s food supply is a "national security issue of the utmost importance." She stated that the border will reopen for livestock trade once increased surveillance and eradication efforts in Mexico begin showing positive results. Rollins has also sought to dispel any notion of political motivation or punitive action against Mexico, reiterating that the decision is solely based on food and animal safety concerns.
This is not the first time the U.S. has taken such measures in response to NWS detections in Mexico. In November 2024, America halted livestock imports after Mexico reported a NWS detection in a cow at an inspection checkpoint near the Guatemalan border. Following that incident, the USDA increased sterile fly deliveries and supported additional surveillance programs, which ultimately led to the resumption of livestock imports in February of this year.
However, relations between the two countries became strained again last month when Mexican authorities began curtailing seven-day flights of USDA planes dispersing sterile flies and imposing import duties on "critical aviation parts, dispersal equipment and sterile fly shipments," according to Rollins in a letter to Esteban Moctezuma Barragán, Mexico’s ambassador to the U.S.
Mexico temporarily avoided the ban by reaching a deal to allow additional flights and waive custom duties. But clearly that agreement was not enough to satisfy U.S. concerns about the advancing threat of NWS.
While NWS does not regularly occur or spread in the United States, it is typically found in South America and the Caribbean. People who travel to these regions, spend time among livestock animals, sleep outdoors, and have an open wound are at greater risk of becoming infected with NWS. The U.S. government advises travelers to take precautions to avoid infection, such as wearing protective clothing, using insect repellent, and promptly cleaning and covering any wounds.
The economic implications of the livestock import suspension are significant for both the U.S. and Mexico. The cross-border trade in cattle, horses, and bison is a multi-billion dollar industry, and the ban will undoubtedly disrupt supply chains and impact prices. Mexican ranchers and livestock producers will face challenges finding alternative markets for their animals, while U.S. consumers may see increased prices for certain meat products.
The suspension underscores the importance of international cooperation in controlling and eradicating animal diseases and pests. The U.S. and Mexico have a long history of collaboration on agricultural issues, and it is crucial that they work together to address the NWS threat and ensure the safe and efficient trade of livestock across the border. Both countries must commit to implementing effective surveillance and eradication programs, sharing information, and resolving any trade-related disputes in a timely and constructive manner. The longer the suspension lasts, the greater the economic damage will be. Finding a mutually agreeable solution is critical to mitigating the long-term impact on both nations.
