The Trump administration shuttered the southern border to all livestock imports on Wednesday to combat the spread of a parasitic larvae that feasts on the live flesh of cattle known as the New World screwworm (NWS).
Department of Agriculture (USDA) Secretary Brooke Rollins announced the closure after receiving reports of a new NWS case in Mexico, according to the USDA. Though U.S. officials announced a phased reopening of cattle imports across the southern border in June, Rollins moved forward with a complete shutdown, as an NWS outbreak would ravage the American agriculture industry and spike the cost of beef, field insiders told the Daily Caller News Foundation previously.
“The United States has promised to be vigilant — and after detecting this new NWS case, we are pausing the planned port reopening’s to further quarantine and target this deadly pest in Mexico. We must see additional progress combatting NWS in Veracruz and other nearby Mexican states in order to reopen livestock ports along the Southern border,” Rollins said. “Thanks to the aggressive monitoring by USDA staff in the U.S. and in Mexico, we have been able to take quick and decisive action to respond to the spread of this deadly pest.”
I have ordered an immediate shutdown of live cattle, bison, and horse trade through the southern U.S.–Mexico border.
This decisive action comes after Mexico confirmed another case of New World Screwworm in Veracruz. As promised, @USDA remains vigilant to ensure the protection… https://t.co/7QQSS3tFfd
— Secretary Brooke Rollins (@SecRollins) July 10, 2025
“Mother Nature gave us a favor,” Colin Woodall, chief executive officer of the National Cattlemen’s Beef Association previously told the DCNF, explaining that screwworms are eradicated when exposed to sterile flies that cause them to die out as they go through their lifecycle.
The USDA announced a comprehensive plan to fight NWS on June 18, which includes aiding Mexico in combating the pest, ensuring vigilance at the southern border and building a domestic sterile fly facility in South Texas, among other initiatives to stymie the northward spread of the NWS.
As the Trump administration is aware of and working to stop an NWS outbreak in the U.S., some industry insiders are concerned for their livestock and the possibility of devastation in the near future.
“This is a significant concern in our industry,” Woodall told the DCNF previously. “This pest is a flesh-eating parasite, and we need to make sure that we can protect ourselves and ultimately eradicate it once it gets to the United States … This could be a fight that takes us a while to ultimately win.”
The Panama-U.S. Commission for the Eradication and Prevention of the Cattle Borer Worm (COPEG) lab in Panama has been producing millions of sterile flies every week, and the USDA pledged to invest $21 million into renovating another facility in Mexico as well. Woodall previously voiced concerns that the lab in Panama is not producing enough sterile flies quick enough to completely obliterate the threat of NWS.
“We know that our efforts will likely require more sterile flies than the facilities in Panama, and eventually, Mexico, can produce,” a USDA spokesperson previously told the DCNF, before it announced the coming Texas facility. “Mexico has been and will continue to be a key partner as we work to eradicate New World screwworm; we cannot do this alone.”
U.S. officials ended a screwworm outbreak in the 1960s through the same method of unleashing sterile flies, but not before the cattle industry suffered a multi-million-dollar loss.
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