As US border reopens to Mexican cattle, concerns persist over screwworm spread

Mexico is bolstering its screwworm containment campaign in northern border states where recent cases have been detected, heightening scrutiny of livestock exports as cross-border trade resumed on Monday under a phased U.S. reopening. The reopening marks ‌the first easing of a U.S. ban imposed more than a year ago to keep out the flesh-eating pest, as imports resumed initially through Arizona. The plan has drawn criticism from some U.S. cattle groups and state officials who argue that resuming imports could increase screwworm risks even as the parasite continues to spread in northern Mexico and has already been detected in Texas and New Mexico.

Mexican Agriculture Minister Columba ‌Lopez said authorities would reinforce the dispersal of sterile flies in Sonora and Chihuahua, a key eradication strategy aimed at preventing the parasite from reproducing. Agriculture Secretary Brooke Rollins told reporters on Monday that ‌the USDA feels it has "taken every step to protect the American (cattle) herd and the American consumer, and so now we can slowly begin to reopen the ports." The USDA plans to open two more New Mexico ports, one in 30 days and another in 60 days, Rollins said. "We don't plan to open any Texas ports anytime soon just because that is where the real activity is," Rollins said. The USDA has identified 46 cases of screwworm in New Mexico and Texas, with ⁠two currently ​active, according to the agency's website. NEW CASES IN MEXICO

A ⁠USDA website on Monday said it reopened the Douglas, Arizona, port to cattle imports from Mexico "guided by overlapping safeguards and a science-based import protocol" agreed upon by the two countries. The USDA will next evaluate the reopening of ports in Santa ⁠Teresa and Columbus, New Mexico, to cattle, bison, and horses. "The opening of ports may be paused if USDA identifies increased risk in Sonora or Chihuahua via post-opening audits or other observations/information," the site said.

The reopening will begin ​with exports of 700 head of cattle per day during the first week, increasing to 900 per day in the second week and gradually rising to around 1,300 per ⁠day, according to Mexico’s National Confederation of Livestock Organizations (CNOG). If additional Chihuahua border crossings are reopened in the fourth quarter, Mexico could export up to 200,000 head of cattle in 2026, with an estimated value of about $420 million at U.S. market prices, CNOG said. Its ⁠base ​scenario for 2027 projects exports of 1.09 million head of cattle, valued at roughly $2.1 billion in the U.S. market.

Chihuahua, one of Mexico's most important cattle-exporting states, has reported 183 confirmed screwworm cases since detecting its first case in July, while neighboring Sonora state has reported two confirmed cases after announcing its first detection last week. Sonora has activated emergency surveillance and containment protocols, while Chihuahua has ⁠intensified inspections, livestock movement controls and treatment campaigns to prevent further spread. The sterile insect technique works by releasing millions of sterilized screwworm flies that mate with wild females but produce no offspring, gradually ⁠driving down the pest population. Mexico recently opened a ⁠sterile-fly production plant in Chiapas, while the U.S. is building its own production facility in Texas, expected to be completed by the spring of 2027. Mexican President Claudia Sheinbaum referred to the sterile-fly technique as a "modern" and "effective" way to fight screwworm.

"That allows us to open the border," Sheinbaum said in her daily press ‌conference.