REDFIELD, Iowa (DTN) -- Just one week after the announcement of the border gradually opening to Mexican cattle, bison, and horses which began July 7, U.S. Secretary of Agriculture Brooke Rollins has closed the ports of entry again due to movement northward of the New World screwworm (NWS).

On July 8, Mexico's National Service of Agro-Alimentary Health, Safety, and Quality (SENASICA) reported a new case of NWS in Veracruz, Mexico, about 370 miles south of the U.S./Mexico border. This is also 160 miles northward of the current sterile fly dispersal grid. The previous closure on May 11 came after the pest was detected 700 miles from the U.S. border. The reopening strategy was planned one port of entry at a time from July 7 through Sept. 15, but now the closure is effective immediately.

"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."

The National Cattlemen's Beef Association (NCBA) praised Rollins' decision to help keep the U.S. beef herd protected from NWS. "A key part of USDA's strategy for protecting American agriculture is continuously monitoring conditions on the ground," said NCBA CEO Colin Woodall. "Secretary Rollins has been working to balance the economic needs of U.S. cattle producers who rely on imports while at the same time protecting the overall U.S. cattle herd. The New World screwworm's northward movement jeopardizes the safety of American agriculture, which is why Secretary Rollins paused cattle movement again until we can push the screwworm further from our border."

Previously, in November 2024, the border was closed when the first case of NWS was found in southern Mexico and reopened on Feb. 1, 2025. Since the May 11 closure, more than 100 million sterile NWS flies were dispersed each week. Since the NWS only mate once, releasing sterile males to mate with the females helps decrease the population.

On June 18, USDA also announced the groundbreaking of a sterile fly dispersal facility in South Texas. This facility will provide a critical contingency capability to disperse sterile flies should an NWS detection be made in the southern United States. USDA is also moving forward with the design process to build a domestic sterile fly production facility to ensure it has the resources to push NWS back to the Darien Gap.

"Secretary Rollins has made significant gains holding Mexico accountable for their role in eradicating the New World screwworm. She successfully removed bureaucratic barriers to the screwworm sterile fly flights and increased surveillance in Mexico. Unfortunately, screwworm continues to move north through Mexico and it's clear that the United States needs a sterile fly facility of our own here at home. We cannot wait any longer and we urge USDA to immediately begin work on a sterile fly facility," Woodall added.

See, "USDA Announces Phased Reopening of the Boarder," https://www.dtnpf.com/…

Also see, "USDA Facility Will Help Combat NWS," https://www.dtnpf.com/…

Jennifer Carrico can be reached at jennifer.carrico@dtn.com

Follow her on social platform X @JennCattleGal

(c) Copyright 2025 DTN, LLC. All rights reserved.