The United States Department of Agriculture (USDA) has suspended the importation of live cattle, horses, and bison through all southern border ports of entry following the continued northward spread of New World Screwworm (NWS) in Mexico. The suspension, announced by U.S. Secretary of Agriculture Brooke L. Rollins, takes effect immediately and will be reassessed monthly based on containment progress.
NWS, a dangerous parasitic fly, has been detected in remote regions of Oaxaca and Veracruz, nearly 700 miles from the U.S. border. The pest poses a serious threat to livestock, wildlife, pets, and in rare cases, humans. The larvae of the NWS fly burrow into the flesh of living animals, causing severe tissue damage and, if untreated, death.
Despite ongoing collaboration between the U.S. and Mexican governments to manage the outbreak, the spread has accelerated in recent months. In response, the USDA’s Animal and Plant Health Inspection Service (APHIS), in coordination with U.S. Customs and Border Protection (CBP), has suspended imports of live animals originating from or transiting through Mexico. Livestock already in holding for entry will still undergo veterinary inspection and treatment before being allowed into the U.S.
This move follows previous actions taken in November 2024, when USDA first suspended trade after the initial detection of NWS in southern Mexico. Imports were briefly resumed in February 2025 after the implementation of a pre-clearance protocol with Mexico. However, the pest has continued to spread throughout Central America and into Mexico despite mitigation efforts, including the aerial and ground release of sterile flies aimed at disrupting the breeding cycle.
The USDA emphasizes that halting livestock imports is a necessary step to limit the pest’s movement through commercial animal trade. The agency is also expanding surveillance between ports of entry, deploying USDA Tick Riders to monitor livestock and wildlife along the border.
Experts stress that successful eradication requires a coordinated approach, including:
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Surveillance and outreach to detect and prevent outbreaks,
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Controlled animal movement to curb transmission, and
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Sterile insect dispersal to suppress breeding populations.
The United States previously eradicated NWS through a decades-long campaign that cost billions. The return of the pest now threatens not only the health and welfare of livestock but also the stability of the U.S. food supply chain.
More information, including affected regions and current trade restrictions, is available on the USDA APHIS Animal Health Status of Regions website.
