Starting Monday, the United States will begin gradually reopening cattle imports from Mexico after a two-month suspension due to concerns over the spread of the screwworm, a dangerous livestock parasite.
Screwworms are parasitic larvae of the Cochliomyia hominivorax fly. Female flies lay their eggs in wounds or mucous membranes of warm-blooded animals, including humans, and those larvae then burrow into the animal. The larvae use tiny hooks in their mouths to eat the flesh of their victim and if that infestation is left untreated, an adult cow can die from it in just a few weeks.
Concerns were raised about the flies in 2024 after an outbreak was discovered in southern Mexico. Imports were restricted in November, then lifted in February before the screwworm made “unacceptable northward advancement” and the ban was implemented in May. USDA Secretary Brooke Rollins said at the time, “The protection of our animals and safety of our nation’s food supply is a national security issue of the utmost importance.”
The USDA announced that the first port to resume operations will be in Douglas, Arizona. The agency said this location poses the lowest risk due to its geographic position and its “long history of effective collaboration” with officials in Sonora, Mexico.
To support containment efforts, the USDA announced last month it would open a new sterile fly dispersal facility in Texas and invest $21 million to update a similar plant in Mexico. That facility will distribute sterile flies that are grown in Panama. No sterile fly factory exists right now in the United States.
Secretary Rollins confirmed the phased plan in a public statement, highlighting efforts by the Trump administration to contain the pest.
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