United States Announces Reopening of its Border to Mexican Livestock After Screwworm Crisis

After seven weeks of closure of livestock trade between the United States and Mexico, the border will again allow the crossing of cattle, bison, and horses from Mexico to the north starting July 7. The United States Department of Agriculture (USDA) announced on Monday that collaboration between both countries to curb the crisis of the screwworm has yielded positive results with monitoring initiatives and the release of sterile flies. “We have not observed a significant increase in reported cases of screwworms in Mexico, nor any movement of the screwworms north in the last eight weeks,” they stated in the document.

The United States assures that the progress achieved in pest control has been possible due to the “resolution of difficulties” in conducting constant flights in Mexico to disperse 100,000 sterile flies per week. Thanks to these organisms, which mix with the fly population in their habitat to ensure no offspring, the pest that devastated livestock in the 1970s has been eradicated. The USDA’s statement also highlights the work of five American teams from the Animal and Plant Health Inspection Service in Mexican territory to “intensify initiatives for monitoring, detection, and eradication of the screwworm.”

The border had been closed to Mexican livestock since May 11, when the closure was announced unexpectedly and unilaterally by the United States, after a series of negotiations where Mexico believed an agreement had been reached. The halt in livestock trade from Mexico, a country that exports over $1 billion in livestock to the U.S. each year, raised tensions among producers and the Sheinbaum government.

The Secretary of Agriculture under President Donald Trump, Brooke R. Rollings, emphasized the role of “vital pest surveillance measures” and “sterile fly dispersal initiatives” in the joint work with Mexican authorities. “These swift actions by the Trump Administration have improved conditions to allow the gradual reopening of selected crossings on the southern border for livestock trade,” she stated, adding that her department will not rest “until we are sure that this devastating pest will not affect American ranchers.”

The first crossing point to reopen traffic for Mexican livestock on the first Monday of July will be Douglas (Arizona), which U.S. authorities consider to be the least risky due to its proximity and connection to Sonora. If there are no adverse effects after the USDA’s evaluation, Columbus (New Mexico) will follow in the next week. Santa Teresa (New Mexico) is set to reopen on July 21, Del Río in Texas on August 18, and finally Laredo on September 15. The opening of additional crossing points will depend on the number of infection cases and ongoing efforts in Mexico “to curb illegal animal movements and implement more rigorous inspection and treatment protocols.”

The USDA has taken this opportunity to ask Mexico for more control over the entry of illegal animals through its southern border. “While Mexico has made significant progress in controlling and monitoring animal movement, additional advancements will help ensure the reopening of remaining U.S. ports,” the agency indicated. Currently, there are 26 recorded cases of human myiasis due to screwworm in Mexican territory, half of whom are hospitalized, with the majority concentrated in Chiapas.