Screwworm Shuts the US-Mexico Cattle Border: What Meat Traders Need to Know

A Century-Old Trade Route Grinds to a Halt

The United States has shut its southern border to live cattle imports, and the reason is a tiny flesh-eating parasite called the New World screwworm. The pest has now been found inside Texas, and the shutdown is sending shockwaves through the North American beef supply chain.

For meat buyers and sellers, this is more than an animal health story. It touches cattle supply, beef prices, and trade flows across the region.

What Is the New World Screwworm?

The New World screwworm is the larva of a fly whose scientific name is Cochliomyia hominivorax. The maggots feed on the living tissue of warm-blooded animals, and in rare cases they can affect humans too.

The region spent decades getting rid of this pest. A long campaign using the "sterile insect technique" pushed it all the way down to Panama by 2006. That method works by breeding male flies, sterilising them, and releasing them so that wild females lay eggs that never hatch.

The barrier in Panama held until 2022. Since then the parasite has moved north through Central America, into Mexico, and now across the US border.

Cases Inside Texas

According to the US Department of Agriculture, the country has confirmed 32 screwworm infestations, with 31 in Texas and one in New Mexico. The cases cover 12 Texas counties and 23 separate premises. The most recent detection, a sheep in Crockett County, was confirmed on 3 July 2026.

In Mexico, nearly 28,000 cases have been recorded since November 2024.

Texas officials have put strict controls in place:

21 Texas counties are under movement restrictions.
Warm-blooded animals cannot leave those areas without a certified inspection first.
All southern ports of entry are closed to livestock trade.
Infected animals cannot be sold or processed for meat.

Why This Matters for the Meat Trade

The border closure hits a trade route built over more than a century. Mexican ranches raise calves that are usually sent north to be fattened in US feedlots and processed in American plants.

Before the closure, the United States imported more than one million cattle a year from Mexico. That is about 4% to 5% of all cattle used for US beef production, according to industry data cited by Texas Public Radio.

The Texas cattle industry alone is worth around 41 billion dollars a year, and state officials warn the outbreak could push beef prices higher in shops. The disruption also adds pressure to a US cattle supply that was already very tight.

The View From Mexico

For Mexican ranchers, the pain is severe. Álvaro Bustillos Fuentes, who leads the Chihuahua Regional Cattlemen's Union, called it "the worst storm in the history of our livestock industry." He pointed to three years of harsh drought, followed by the return of the parasite and the loss of the US market.

He said only three border closures have happened in more than 120 years of cattle trade with the United States. The others came during the Mexican Revolution and a foot-and-mouth disease outbreak.

The numbers he shared are striking:

Chihuahua normally exports about 500,000 head of cattle a year.
Producers are losing roughly 1,000 dollars per head, which he estimates at 500 million dollars a year in lost opportunity for the state.
About 1.2 million head that would normally move north are now stuck in Mexico, pushing local prices down.

The Race to Rebuild the Fly Barrier

Both governments are now trying to expand sterile-fly production, but much of the new capacity is still being built.

The main existing facility, run by a US-Panama commission known as COPEG, makes about 100 million sterile flies a week. The Food and Agriculture Organization said in June that the emergency could need up to 600 million flies a week.

New projects are on the way:

In late June, US and Mexican officials opened a sterile-fly plant in Metapa de Domínguez, in the Mexican state of Chiapas. The USDA is investing 21 million dollars and expects it to add 60 to 100 million flies a week.
The United States is building a plant at Moore Air Base in Edinburg, Texas, with first output targeted for November 2027 and full capacity of 300 million flies a week.

The timing is the real problem. The region is expanding production only after the pest has already crossed into the United States.

What Buyers and Sellers Should Watch

The screwworm crisis is now a shared US and Mexico problem, and how the two governments respond will shape trade for months to come. Mexican industry leaders want science-based protocols and inspections rather than a blanket border closure.

For the wider market, the key questions are simple: how long the border stays shut, whether beef prices climb further as North American supply tightens, and how fast the new sterile-fly plants can come online.

The US Centers for Disease Control and Prevention says there are no locally acquired human cases, and that the risk to people remains very low.