On May 11, 2025, U.S. Secretary of Agriculture Brooke L. Rollins announced the immediate suspension of live cattle, horse, and bison imports through southern border ports of entry from Mexico. This decision was made in response to the continued and rapid northward spread of the flesh-eating New World Screwworm (NWS), a dangerous parasitic insect that poses a serious threat to livestock.
The suspension, which takes effect immediately, comes after recent detections of NWS in the Mexican states of Oaxaca and Veracruz, around 700 miles from the U.S. border. The nited States Department of Agriculture (USDA) stated it continues to work closely with Mexican authorities, but the northward progression of the pest presents an unacceptable risk to U.S. animal health and food security.
What is the New World Screwworm?
The New World Screwworm is a flesh-eating fly whose larvae burrow into the living tissue of warm-blooded animals, causing severe wounds and often death if left untreated. This dangerous pest can infect livestock, pets, wildlife, and in rare cases, humans.
Although the U.S. and Mexico had successfully eradicated NWS decades ago through costly and prolonged efforts, the pest has re-emerged in southern Mexico in recent months, even in remote areas with minimal animal movement.
Since the first confirmed case in Mexico in November 2024, the parasite has steadily spread across Central America, including Panama, Costa Rica, Nicaragua, Honduras, Guatemala, El Salvador, and Belize, before reaching parts of southern Mexico, heightening regional alarm.
Import Suspension and Safety Measures
The USDA’s Animal and Plant Health Inspection Service (APHIS), in collaboration with U.S. Customs and Border Protection (CBP), will enforce the suspension until a significant window of containment is achieved. This suspension will be reviewed on a monthly basis.
Livestock currently held at ports of entry will undergo standard veterinary inspections and treatments by APHIS to ensure they are not carriers of New Castle disease (NWS) before they are permitted to enter the U.S.
“This is not about politics or punishment of Mexico, rather it is about food and animal safety,” said Secretary Rollins. “The protection of our animals and the safety of our nation’s food supply is a national security issue of the utmost importance.”
She highlighted the continued cooperation with Mexican authorities, stating that discussions are ongoing to build on existing surveillance and eradication strategies. A data review is scheduled within two weeks to evaluate progress and adjust strategies accordingly.
To curb the spread of NWS effectively, the USDA is implementing a comprehensive three-pronged strategy. The first pillar involves active surveillance and public education, aimed at increasing awareness, promoting early detection, and preventing outbreaks.
The second step includes controlled animal movement, focusing on reducing the spread of the parasite through livestock trade. The third approach applies the Sterile Insect Technique (SIT), a biological control method that involves releasing sterile male flies into affected areas to disrupt reproduction and reduce NWS populations.
APHIS is currently deploying both aerial and ground teams to distribute sterile flies in high-risk zones across southern Mexico and Central America. Additionally, USDA’s “Tick Riders” are patrolling the U.S.-Mexico border, monitoring both domestic livestock and wildlife for signs of infestation, especially in areas beyond formal ports of entry.
The USDA acknowledges that suspending livestock imports may impact trade but highlights that failing to contain the NWS outbreak could lead to billions in losses and take years to recover. The department has reaffirmed its commitment to resuming trade once containment goals are achieved and surveillance data shows a positive trend.
