U.S. Secretary of Agriculture Brooke L. Rollins on Sunday announced the imme-diate suspension of live cattle, horse and bison imports through U.S. ports of entry along the southern border due to the continued rapid northward spread of New World screwworm in Mexico. NWS was recently detected in remote farms with minimal cattle movement as far north as Oaxaca and Veracruz, about 700 miles away from the U.S. border. The first case of NWS in Mexico was reported to the U.S. in November 2024. When NWS fly larvae burrow into a living animal, they cause serious, often deadly damage to the animal. NWS can infest livestock, pets, wildlife, occasionally birds, and in rare cases, people. Over the last two years, the screwworm has spread north throughout Panama and into Costa Rica, Nicaragua, Honduras, Guatemala, El Salvador, Belize and Mexico. The U.S. and Mexico continue efforts to interdict and eradicate NWS in Mexico and work in good faith. However, despite these efforts and the economic impact on both countries due to this action, there has been unacceptable northward advance-ment of NWS and additional action must be taken to slow the northern progression of this deadly parasitic fly. As such, effec-tive immediately, the USDA Animal Plant Health Inspection Service in conjunction with Customs and Border Protection will restrict the importation of live animal commodities originating from, or transit-ing Mexico. The suspension will continue on a month-by-month basis. The USDA will collaborate with Mexico and review data and metrics in two weeks. Any livestock currently in holding for entry into the U.S. will be processed normally, this includes an APHIS port Veterinary Medical Officer inspection exam and treatment to ensure screwworm in Mexico,” Rollins said. “Secretary Berdegué and I have worked closely on the NWS response; however, it is my duty to take all steps within my control to protect the livestock industry in the United States from this devastating pest. Once we see increased surveillance and eradication efforts, and the positive results of those actions, we remain committed to opening the border for livestock trade. This is not about politics or punishment of Mexico, rather it is about food and animal safety.”
Effective eradication requires a threepronged approach: robust active field surveillance with education and outreach to ensure prevention, treatment, and early detection; controlled animal movement to limit spread; and sustained sterile insect dispersal.
Suspending livestock transport through southern ports of entry will assist in the effort to limit northbound transport of NWS through livestock commerce, and will allow the U.S. to reassess whether current mitigation standards remain sufficient. It is important to note the northward spread of NWS is possible through natural wildlife movements, including wildlife that transit the border region without impediment.
USDA is taking all possible actions to monitor for, and limit, the northward movement of NWS, including the utilization of the USDA Tick Riders to monitor livestock and wildlife along the southern border region, between the ports of entry, for the presence of NWS.
APHIS is releasing sterile flies through aerial and ground release at strategic locations, focusing on Southern Mexico and other areas throughout Central America. A complete list of regions APHIS recognizes as affected by NWS as well as more detailed information on trade restrictions can be found on the USDA APHIS Animal Health Status of Regions website.
The U.S. previously and successfully led the eradication of NWS in the U.S. and Mexico, however this cost billions of dollars and took decades. Recent detections in Mexico show NWS is back and remains a serious threat.