US to reopen southern cattle ports in stages after year-long screwworm closure

The US Department of Agriculture (USDA) announced on 24 July 2026 a coordinated, phased reopening of the southern ports that had been closed to cattle to keep New World screwworm out of the United States. Beginning on 24 August 2026, the Douglas port of entry in Arizona would open to cattle trade from Mexico. The whole process was made contingent on Mexico's adherence to the two countries' Joint Action Plan, and every animal entering through these ports would undergo a full USDA inspection to make sure it showed no sign of screwworm.

USDA said the Douglas port borders the Mexican state of Sonora. By the department's account, the closest active case to Douglas was about 325 miles away and had been detected on 22 July 2026. Alongside Douglas, the department said it would simultaneously begin the operational steps needed for later openings at the Santa Teresa and Columbus ports in New Mexico.

After evaluating the success of the first opening and any change in impacts or risk assessment, USDA's Animal and Plant Health Inspection Service (APHIS) would then consider reopening Santa Teresa and Columbus to live cattle, bison and horses. USDA said the timeline would stay flexible and could be adjusted according to Mexico's progress on the Action Plan milestones, and that openings could be paused if post-opening audits or other information showed increased risk in Sonora or Chihuahua.

According to USDA, Sonora and Chihuahua have for many years maintained a strong animal health infrastructure built on successful disease control. It identified them as the lowest-risk Mexican states for the pest because of their well-established inspection programmes and their distance from southern Mexico, where most cases were concentrated.

Agriculture Secretary Brooke L. Rollins said that protecting the United States from screwworm and pushing the pest out of Mexico and back to the Darien Gap was a top priority for USDA. "The closure of the Southern ports of entry for the last year has been a tough but necessary action to control the spread of NWS in Mexico and protect the American livestock industry," she said, adding that it was now safe to reopen the Douglas port in 30 days "to resume the hundreds year old movement of cattle."

According to a USDA statement of 9 July 2025, the ports were first closed to Mexican cattle, bison and horses on 11 May 2025, after detections further north in Oaxaca and Veracruz. A phased reopening had been planned from as early as 7 July 2025, but on 9 July Mexico's animal health agency SENASICA reported a new case in Ixhuatlán de Madero, Veracruz, about 370 miles south of the US border, and the southern ports were shut again.

The Texas Tribune reported on 24 July 2026 that there had been 42 screwworm cases in the United States as of that day, all but one of them in Texas. Texas Agriculture Commissioner Sid Miller welcomed the decision as the right move for ranchers and consumers, saying the prolonged closure had taken a toll on producers and disrupted supply chains. He also said the decision should have come sooner and that USDA's screwworm response had not gone far enough; the report carried no USDA response to that criticism.

APHIS describes the New World screwworm (Cochliomyia hominivorax) as a fly whose larvae burrow into the flesh of a living animal and cause serious, often deadly, damage. It can infest livestock, pets, wildlife, occasionally birds and, in rare cases, people. Signs include irritated behaviour, head shaking, the smell of decay and maggots in wounds. Female flies lay 250 to 500 eggs in the exposed flesh of warm-blooded animals.

Using the sterile insect technique, APHIS says, the United States eradicated screwworm in 1966 and eliminated a small outbreak in the Florida Keys in 2017. In this method, released sterile male flies mate with wild females, which then lay unfertilised eggs.

Photo: Judy Gallagher / Wikimedia Commons (CC BY 2.0)

Sources: USDA, The Texas Tribune, USDA APHIS, Wikipedia