Horse Smuggling Puts Holes in the US Fight Against Screwworm

Near the small town of Redford, Texas, sheriff's deputies stopped a truck pulling a trailer and found six horses inside. The horses had been secretly brought across the Rio Grande from Mexico without any health checks or legal paperwork. The discovery showed a serious gap in the United States' effort to stop a dangerous parasite called New World screwworm from spreading into the country.

Screwworm is a flesh-eating parasite — a type of fly whose larvae burrow into the skin of living animals and feed on them. The US has been battling to keep it out, but the fly began showing up in US cattle in June 2025. To fight back, the government banned cattle imports from Mexico for more than a year, sent inspectors on horseback to patrol the border, and even released huge numbers of sterile flies to stop screwworms from reproducing.

The six horses caught near Redford in late May were not infected with screwworm, but their capture shone a light on a part of the problem that hasn't gotten much attention. While the US was cracking down on legal cattle trade and costing businesses billions of dollars, criminals were quietly moving horses and other animals across remote stretches of the border. Law enforcement officers say these smuggling networks are linked to Mexican drug cartels.

The risk is huge. A screwworm outbreak in the past killed thousands of animals before the pest was wiped out in the 1960s. Experts say a big outbreak could cost the Texas economy up to $1.8 billion, and beef prices are already at record highs partly because of the long ban on Mexican cattle imports.

Smuggled animals range from expensive racehorses and rodeo horses to dogs used in illegal fighting rings and even exotic animals like primates, bears, and tigers. Mexico's animal health agency has confirmed more than 2,000 horse cases of screwworm since the outbreak began in 2024. A researcher named Oscar Rico explained the danger: 'These kinds of movements represent a risk because they allow the fly to travel much faster than it could move naturally.'

Reuters reporters spent a week in August visiting three small communities along the Texas-Mexico border, riding along with local officers and talking to sheriffs, animal doctors, and former Border Patrol agents. Everyone described how hard it is to watch hundreds of miles of rough, wild land where animals, drugs, and people can cross without being detected.

Sergeant Deputy Sheriff Jaime Sanchez of Presidio County said smuggled horses can sell for at least $30,000 on the black market. Smugglers can charge less than legal sellers because they skip the required paperwork, taxes, and health checks. The horses are often taken to Houston or Dallas, where they are sold for farm work, racing, or charrería — Mexico's traditional horse sport. Sanchez's department has stopped more than 50 smuggled horses in just the past two years.

Redford is nearly a ghost town, with fewer than 20 families, empty homes lining its roads, and a shuttered school. It sits along a shallow stretch of the Rio Grande where smugglers walk horses across the river and load them into waiting trailers. Sanchez said criminal groups pay people $500 to $1,000 per horse to help with the crossing, and he linked the operation to La Linea, a cartel labeled a Foreign Terrorist Organization by the US government in July 2025.

US officials have not proven that any of the country's 48 confirmed screwworm cases came from smuggled animals, but many experts believe that number is too low. Animals crossing the border illegally skip official checkpoints, so no one tests or treats them for infections. Scientists and animal doctors told Reuters that this creates the same disease risks that officials have already flagged in illegal cattle movements from Central America.

The USDA's top inspector, John Walk, said animal smuggling at the southern border 'seems more pronounced' lately and called it a national security issue made worse by screwworm. 'It could be a vector,' he said, meaning smuggled animals could be a pathway for the parasite to spread. In July, he traveled to Brownsville, Texas, to warn local law enforcement, and Agriculture Secretary Brooke Rollins posted on social media in August saying the department was 'cracking down' on illegal livestock movements.

One morning in August, about 80 law enforcement officers gathered in Zapata County for a major sweep as part of Operation Lone Star Task Force. Patrol trucks rolled down highways, and officers searched waterways for signs of illegal activity. Investigators paid close attention to horse trailers, which blend into rural life and are easy to overlook.

Officers in Goliad County pointed to a 2024 case in which deputies stopped a livestock trailer and found 14 people hidden inside, along with a neglected horse. The driver said he had been paid $10,000, and investigators determined the vehicle was tied to human smuggling. Sheriff Roy Boyd said, 'The revenue streams for the cartels are far more diverse than people have ever suspected.'

Animal smuggling routes create a special problem for screwworm control because infected animals that move illegally may never see a veterinarian. Tawnee Preisner, who runs a horse rescue group in Tennessee, said her team has found horses with serious wounds suggesting smugglers may be hiding drugs inside the animals. She said that if a smuggler's horse gets screwworm, no one will report it — they will simply get rid of the horse and keep moving.