The U.S. has halted all livestock imports from Mexico after deadly flesh-eating screwworms were detected, exposing troubling patterns in cross-border cooperation and raising concerns about America’s food security.
At a Glance
- U.S. Secretary of Agriculture Brooke Rollins suspended all cattle, horse, and bison imports from Mexico after detection of the New World Screwworm parasite
- The flesh-eating parasite, eradicated in the U.S. since 1966, can cause fatal infections in mammals by laying eggs in wounds
- Mexico restricted U.S. planes dispersing sterile flies and imposed import duties on equipment used to control the parasite
- The suspension will be reviewed on a month-by-month basis as U.S. officials assess the risk to border states
- The last U.S. screwworm infestation took 30 years for the cattle industry to recover from
Critical Border Action to Protect U.S. Agriculture
The U.S. Department of Agriculture has taken immediate action to prevent a potentially devastating parasite from entering the country through the southern border. Secretary of Agriculture Brooke Rollins announced the suspension of live cattle, horse, and bison imports from Mexico after authorities confirmed a case of New World Screwworm in Mexican livestock. The parasite, which was eradicated from the United States nearly six decades ago, poses a significant threat to American animals and the nation’s food supply, with officials particularly concerned about risks to border states like Texas where wildlife regularly crosses between countries.
The dangerous parasite was detected on remote farms in Mexico, approximately 700 miles from the U.S. border, prompting serious concerns about its northward spread. This marks the second suspension in recent months, following a previous halt to Mexican livestock imports in November after detection near the Mexico-Guatemala border. That suspension was lifted in February 2025 after increased surveillance measures were implemented, but new detections have forced U.S. officials to reinstate the ban to protect American agriculture from what could become a catastrophic infestation.
The Devastating Impact of Screwworm Infestations
New World Screwworm is not an ordinary parasite but a particularly gruesome threat to livestock and wildlife. The parasitic fly lays eggs in wounds or body openings of mammals, where the hatching larvae feed on living tissue, causing extensive damage that can lead to death if untreated. Symptoms of infection include isolation, loss of appetite, irritated behavior, head shaking, and the unmistakable smell of decay. The adult flies resemble common houseflies but have distinctive features that help specialists identify them as they spread through animal populations.
The United States successfully eradicated the New World Screwworm in 1966 using an innovative technique involving the release of sterile male flies, which prevents reproduction when they mate with wild females. This same approach has been used in recent decades to maintain a buffer zone in Panama, preventing the northward spread of the parasite from South America. The screwworm is typically found in South America and the Caribbean, which also poses potential risks to travelers with open wounds visiting these regions who could inadvertently transport the parasites back to the United States.
International Tensions Over Parasite Control
The livestock import suspension has highlighted growing tensions between the United States and Mexico regarding agricultural cooperation. In April, Mexico restricted U.S. planes dispersing sterile flies—a critical control method—and imposed import duties on related equipment, hampering eradication efforts. Mexican officials have criticized the ban, arguing that established protocols already ensure cattle are free of screwworms before crossing the border, but U.S. officials determined these measures were insufficient to protect American agriculture from what could be a devastating economic blow.
Mexican authorities temporarily avoided the ban earlier by allowing additional flights of sterile flies and waiving customs duties on essential equipment, but the recent detection has forced the USDA to implement stronger measures. Secretary Rollins emphasized that the suspension will be reviewed on a month-by-month basis as officials monitor the situation. While there are currently no confirmed cases of New World Screwworm in Texas or other border states, the proximity of infestations in Mexico has raised significant concerns about potential spread through wildlife that regularly crosses the international boundary.
