The New World Screwworm emergency comes amid broader tensions between the U.S. and Mexico over agricultural trade.
U.S. Secretary of Agriculture Brooke Rollins has sent a formal letter to her counterpart in Mexico demanding immediate action to remove restrictions on USDA aircraft and waive customs duties on eradication equipment. These barriers are critically impairing the U.S. response to the growing spread of New World Screwworm (NWS) in southern Mexico.
“Every delay in granting full operational authority and eliminating customs barriers undermines our collective ability to carry out this emergency response,” Rollins said in a USDA news release.
Additionally, Secretary Rollins informed the government of Mexico, “…that if these issues are not resolved by Wednesday, April 30, USDA will restrict the importation of animal commodities, which consist of live cattle, bison, and equine originating from or transiting Mexico to protect the interest of the agriculture industry in the United States.”
The USDA continues to take aggressive action to stop the spread of New World Screwworm before it reaches the U.S. border. NWS is a parasitic fly that attacks warm-blooded animals, including livestock and wildlife, by laying larvae in open wounds. The larvae feed on living tissue, causing severe injuries that often lead to death if left untreated.
The New World Screwworm emergency comes amid broader tensions between the U.S. and Mexico over agricultural trade. Over the past two years, the countries have clashed over Mexico’s attempts to ban imports of genetically modified (GM) corn for human consumption, a move the U.S. argues violates the United States-Mexico-Canada Agreement (USMCA). The dispute led to formal consultations under the USMCA framework, and the issue remains unresolved. In addition, concerns have risen around Mexico’s slower-than-expected approvals of biotechnology products, sanitary and phytosanitary measures that U.S. exporters say lack transparency, and enforcement barriers that hinder U.S. agricultural exports ranging from potatoes to dairy products.
These simmering trade frictions add weight to USDA’s urgent demands for cooperation in fighting the New World Screwworm outbreak. Agriculture remains a cornerstone of the U.S.-Mexico economic relationship, with two-way agricultural trade exceeding $73 billion in 2023.
The U.S. successfully eradicated NWS from its territory in 1966 through a sterile insect technique program, later expanding efforts into Mexico and Central America to maintain a protective barrier. However, recent detections in Mexico signal a resurgence of the pest, sparking concerns that it could again threaten U.S. livestock, wildlife and food security.
An outbreak of NWS in the U.S. would have devastating consequences, leading to millions of dollars in livestock losses and significant costs for treatment and containment. Continuous vigilance and international cooperation are critical to keeping the pest at bay.
More information on the New World Screwworm
The New World Screwworm (Cochliomyia hominivorax) is a parasitic fly that poses a deadly threat to warm-blooded animals. Adult flies lay their eggs in open wounds or body openings of livestock, wildlife and pets. After hatching, the larvae feed on living tissue, creating severe wounds that can quickly become fatal if untreated.
NWS infestations were once widespread across the southern United States, causing major losses in cattle, sheep and wildlife populations. The USDA, in partnership with Mexico and Central American countries, eradicated the pest through a sterile insect technique program, a decades-long effort completed in the 1960s and 70s. Since then, maintaining a screwworm-free zone has been critical to protecting North American agriculture and ecosystems.
Recent detections of NWS in Mexico have renewed fears of northward spread. An outbreak in the U.S. would not only endanger livestock health but also cause millions of dollars in economic losses, increased veterinary costs and significant trade disruptions.
Prevention hinges on early detection, aggressive eradication and close cooperation between international partners.
