Smuggled horses expose border blind spot in U.S. screwworm fight
By Cassandra Garrison
REDFORD, Texas, Sept 5 (Reuters) - The trailer stood out on a quiet ranch road near this tiny Texas border town, and the deputies who stopped it found six horses that had not entered the United States legally. There were no health certificates, no customs records and no evidence the animals had passed through a proper livestock inspection. They crossed the Rio Grande from Mexico through a smuggling network, according to investigators, in the kind of movement that U.S. border defenses are not designed to catch.
The horses were not carrying New World screwworm. But for the officials now fighting the parasite, the late-May interception has become a case study in what remains outside their control.
New World screwworm is the larval stage of a fly that feeds on living tissue and can kill cattle, horses and other animals if untreated. Eradicated from the United States in the 1960s, it has swept through parts of Mexico since 2024. Mexico’s animal health agency, Senasica, has confirmed more than 2,000 equine cases since the outbreak began in 2024. Texas cattle began testing positive in June, and federal officials have now confirmed 48 animal infections in the United States. The response has included a ban on Mexican livestock imports lasting more than a year, inspectors on horseback and a program that releases sterile flies to interrupt the pest’s life cycle.
The import ban has carried its own consequences. It disrupted a livestock trade worth billions and helped push U.S. beef prices to record highs. The Trump administration has partially reopened the border to Mexican livestock to relieve consumers, even as Mexico’s outbreak continues to spread.
A screwworm outbreak is not just an animal health problem. Before the pest was eradicated in the U.S., it killed thousands of animals. Texas experts estimate that a widespread new outbreak could cost the state’s economy as much as $1.8 billion.
Federal officials have argued for more than a year that illegal livestock moving up from Central America helped bring screwworm to the region. Reuters reporting along the Texas-Mexico border found a parallel problem: animals are still moving illegally into the United States from Mexico, often on the same remote routes used for drugs and migrants.
Some of those animals are destined for legitimate-looking markets. Officers have intercepted high-value horses bought for racing or rodeo, horses tied to the traditional Mexican sport of charrería, cattle, dogs used in fighting rings and, in recent years, exotic animals including primates, bears and tigers, according to USDA officials, law enforcement and animal-industry experts.
A ghost town and a crossing spot
Presidio County Sheriff’s Sergeant Deputy Jaime Sanchez, who investigated the Redford trailer case, said the illegal horse trade is a business that avoids paperwork, taxes and veterinary costs. A smuggled horse can sell for at least $30,000 on the black market, he said, undercutting legal sellers and leaving no trace of where the animal came from. Many are taken to Houston or Dallas, he said, for ranches, racing or charrería.
Sanchez’s department has intercepted more than 50 smuggled horses in the past two years, usually by pulling over trailers in remote areas where horse trailers are uncommon. Redford, known historically as El Polvo, or the Dust, is now a near-ghost town of fewer than 20 families, with abandoned houses and a shuttered school. In August, Sanchez drove to a low bank of the Rio Grande and pointed to the route used in the May case. Smugglers walked the horses through the river, crossed private land owned by an elderly resident and loaded them into a waiting trailer just beyond view.
“It’s easy for them to pay someone $500 or $1,000 per horse to cross it, load it onto the trailer and drive off,” Sanchez said.
Sanchez said La Linea, a Mexican cartel the Trump administration designated as a Foreign Terrorist Organization in July, controls much of the illicit traffic in the area. The FBI has linked the group to border crime. “Since these are security matters, the issue of screwworm always comes up because it can hit economies very hard,” he said. “In reality, we are very concerned.”
Mexico’s environmental regulator Profepa said it cooperates with the U.S. Fish and Wildlife Service on trafficking investigations and the return of live animals. Spokespeople for Mexico’s security, agriculture and foreign ministries declined to comment.
An invisible path for disease
The USDA has not said how screwworm reached the United States, and investigators have not tied any of the 48 confirmed animal cases to smuggling. The agency said epidemiological work is ongoing. Many veterinarians and scientists believe the official count may be low, because smuggled animals do not pass through testing or treatment.
“These kinds of movements represent a risk because they allow the fly to travel much faster than it could move naturally,” said Oscar Rico, a researcher at Mexico’s National Autonomous University who co-authored a study on how animal movements could spread screwworm.
In Texas, ranchers are watching the uncertainty with unease. Ricardo Ramirez, 57, has spent his life on a family ranch in Zapata County that has been in his family since the 1940s. “Screwworm didn’t affect us for the last 50 years and lo and behold, here we are again with this thing upon us,” he said from beneath the shade of a tree.
The federal response has expanded beyond standard livestock checks. USDA Inspector General John Walk told Reuters that smuggling at the southern border “seems more pronounced,” and he described animal trafficking as a national security issue. “It could be a vector,” he said. Walk traveled to Brownsville, Texas, in July to raise the concern with local authorities. Agriculture Secretary Brooke Rollins said in early August that the department was “cracking down” on illicit livestock movements.
Trailers, drones and the cartel economy
One August morning in Zapata County, about 500 miles southeast of Presidio, a joint sweep brought about 80 officers from the Operation Lone Star Task Force to roads, waterways and remote staging areas. Their focus included horse trailers, a vehicle type so common in Texas ranch country that it can move through rural areas without raising suspicion.
Goliad County Sheriff Roy Boyd pointed to a 2024 traffic stop to explain why. Deputies stopped a livestock trailer and found 14 people, plus a neglected horse, inside. The driver said he had been paid $10,000, and investigators connected the vehicle to human smuggling. “Most people, when they think about the cartel, they think about either drugs or illegal aliens,” Boyd said. “The revenue streams for the cartels are far more diverse than people have ever suspected.”
Further west, in Terrell County, Sheriff Thaddeus Cleveland watched feral cattle cross the Rio Grande from his pickup. Plastic bottles and clothing discarded by migrants dotted the dry landscape. Cleveland, a former Border Patrol agent, said horses have long been used to move drugs over terrain too rough for vehicles. Seized horses often ended up with the USDA and were given to mounted agents, he said.
The risk, animal-health officials say, is that a smuggled animal may never come into contact with a veterinarian. If it is infected, it can carry screwworm well beyond the crossing point before anyone notices. Tawnee Preisner, founder of the Tennessee-based Horse Plus Humane Society, said her organization has treated horses with neck wounds, metal tracheotomy tubes and deep tissue pockets that raised concerns about drugs or contraband hidden inside the animals. The FBI contacted the group in 2025 for information on horse smuggling, she said.
“When horses are being used to move drugs and humans, if a horse gets screwworm, they’re not going to report it,” Preisner said. “They’re just going to shoot the horse, bury it and keep going.”
(Reporting by Cassandra Garrison; Editing by Emily Schmall and Rod Nickel)