The United States will begin accepting limited livestock imports from Mexico on Aug. 24 through the Douglas, Arizona, border crossing, easing a yearlong ban imposed over the spread of a flesh-eating parasite known as the New World screwworm fly.

The ban has strained cattle and beef industries on both sides of the border. In the U.S., it deepened an existing livestock shortage and added pressure to an already tight beef supply chain, while in Mexico it hit a ranching sector already weakened by drought and the loss of a cattle export business that generated $1.2 billion for the country last year.

The reopening starts at Douglas, which borders Agua Prieta in Mexico's Sonora state. If it goes smoothly, the U.S. Department of Agriculture could permit imports through additional ports. Shipments will initially face restrictions designed to prevent the parasite from spreading — a concern that has already materialized, with authorities battling cases in Texas and New Mexico.

The screwworm takes its name from the maggots' habit of burrowing — or "screwing" — into a wound, according to the USDA Animal and Plant Health Inspection Service. Any warm-blooded animal, including wildlife and pets, can be infested, and occasionally even humans.

In Mexico, the outbreak was first detected in November 2024 and has since spread to 30 of the country's 32 states. The most recent arrival is Sonora, where the first case was reported Wednesday in the community of Munihuasa, near the borders with Chihuahua and Sinaloa — two states where infections have also proliferated.

Mexico currently has 1,969 active screwworm cases, less than half the number reported a year ago. Authorities describe the decline as evidence of progress in containing the outbreak, while acknowledging that full eradication will take time.

Against that backdrop, ranchers in Sonora are preparing to resume live cattle exports — among them Martín Alfonso Ibarra, who at daybreak takes advantage of the cooler hours in northern Mexico's desert to oversee the milking of his cows and tend to 16 prized calves he hopes will soon head north. But optimism is tempered by new U.S. controls expected to slow cross-border shipments.

"This is not over yet," said the 58-year-old rancher, noting that the export halt cut his income by 40% last year.

Under the protocol defined by U.S. authorities, only 700 cattle per day will be allowed through in the first week of reopening. The cap will rise to 900 in the second week and then gradually increase until it reaches 1,300 cattle per day, veterinarian Arturo Ruiz, responsible for animal health for the state of Sonora, told The Associated Press.

The new rules also require cattle to be fitted with radio-frequency identification tags in their ears and screened by electronic readers and trained dogs. Officials from the U.S. Department of Agriculture will conduct the inspections before allowing the Mexican cattle to cross into Arizona, Ruiz explained.

Mexico accepted the U.S. protocols, but the restrictions have frustrated some local ranchers.

"We are at a complicated moment when we need authorities to think less politically and more technically and reasonably," said Juan Carlos Ochoa, president of the Regional Livestock Union of Sonora, referring to tensions between the Mexican and U.S. governments when the ban was first imposed in May 2025.

Ochoa said the new U.S. restrictions would limit shipments and argued that a greater flow of cattle across the border is needed to address supply shortages in both countries.

Although both countries felt the effects of Washington's decision, the impact was greater in the U.S., particularly for consumers facing record-high beef prices that led some to cut back on meat. Juan Carlos Anaya, general director of agricultural consulting firm Grupo Consultor de Mercados Agrícolas, said U.S. ranchers were unable to make up the supply shortfall, contributing to closures at some meat-processing plants and hurting feedlot operations.

Before the border closure, Mexico exported about 1.2 million head of cattle to the United States each year, mainly from its northern states. When exports were suspended, Mexican ranchers turned to the domestic market, where they sold their cattle for nearly 40% less than they had received in the U.S. — a loss of income that forced many to sell some of their cattle or cut spending and investment.

Back in Sonora, in the stifling August heat of the capital, Hermosillo, Ibarra was cautiously optimistic about finally sending his 16 calves to the U.S. But he said he would temper his expectations until October, when the cattle have gained enough weight and the sale could be finalized.

"There's no need to get too excited," he said.

Source: Fortune