In the dusty heart of Texas cattle country, a sense of uneasy déjà vu hangs over the ranches. Fifth-generation rancher Kip Dove still remembers, with an almost visceral clarity, the grisly scenes from the last major screwworm outbreak in 1973. Back then, at just eight years old, Dove would ride out at dawn, a bottle of tar-like medicine and a revolver at his side, prepared to treat — or, in the worst cases, euthanize — cattle whose wounds had become infested by the flesh-eating larvae of the screwworm fly. The air, he recalls, was thick with the stench of rotting flesh and the anxious barks of cattle dogs, as cowboys worked desperately under the glare of truck headlights to save what livestock they could.
Now, more than fifty years later, that nightmare is threatening to return. According to Reuters, the notorious screwworm — a parasitic fly officially eradicated from the U.S. in 1966 — is once again advancing northward from Central America. The stakes are enormous: the U.S. Department of Agriculture (USDA) estimates that a new outbreak could inflict $1.8 billion in damage on Texas’s economy alone. And with beef prices already hovering at record highs, any disruption to the cattle supply could send them even higher, impacting dinner tables across the nation.
The screwworm’s life cycle is a rancher’s worst fear realized. Female flies lay hundreds of eggs in even the smallest wound on a warm-blooded animal. When the eggs hatch, the larvae burrow into living flesh, feeding and enlarging the wound until, if left untreated, they kill their host. "The smell is bad, and some of the wounds are horrific. You have humongous holes in these animals teeming with worms," Dove told Reuters. "I don’t know if I could handle it if it happens now."
This isn’t just a Texas problem. Ranchers across Central America and Mexico are already battling a surge in cases. In Chiapas, Mexico — ground zero for the current outbreak — livestock infestation started emerging last year and is now increasing by roughly 10% each week. Nearly 50,000 cases have been reported from Panama to Mexico so far, as detailed by the Panama-United States Commission for the Eradication and Prevention of Screwworm. The problem has even spilled over into humans and pets, though animals remain the primary victims.
As the threat intensifies, the U.S. is scrambling to mount a defense. Washington has halted cattle imports from Mexico and invested millions in a new sterile fly production plant in Metapa, Mexico, though it will take about a year before it’s operational. In the meantime, the USDA is planning to resurrect its long-dormant fly production plant in Mission, Texas, which once churned out 96 trillion sterile flies before being shut down in 1981. Texas officials have already scattered 100 screwworm traps along the border, and USDA inspectors known as Tick Riders — famed for patrolling the border on horseback — have been tasked with preventive treatments for any cattle and horses they find in the area.
But the numbers are daunting. The USDA estimates that 500 million sterile flies need to be released each week to push the screwworm back to the Darien Gap, the narrow jungle barrier between Panama and Colombia. The world-renowned biological facility in Panama, which has operated since 2006, can currently produce only 100 million sterile flies per week. "It’s an overwhelming situation at this point," Dr. Thomas Lansford, assistant state veterinarian at the Texas Animal Health Commission, told Reuters. "Screwworm is obviously doing well in Mexico, and they’re up against the same challenges we are."
The sterile fly technique, developed decades ago, remains the most effective tool for controlling screwworm. Biologists breed flies in a pungent mix of egg, milk, and powdered hemoglobin, then expose them to radiation to render them infertile. Released into the wild, these sterile males mate with females, resulting in eggs that never hatch. Until 2023, sterile flies were dropped into the Darien Gap to maintain a biological barrier. Now, with the outbreak spreading, the focus has shifted to Mexico, but the sheer scale of the problem is stretching resources thin.
For ranchers on the ground, the threat feels all too real — and exhausting. Treatment is low-tech and labor-intensive: each maggot must be scraped out by hand, the wound cleaned, and insecticide applied. In 1973, Dove could rope cattle for treatment until 2 a.m. and still make it to school the next morning. Now, at 60, he wonders if his body — battered by decades of ranch work — could keep up if another outbreak hits. The labor shortage only compounds the problem. "There are no cowboys anymore," Isaac Sulemana, a rancher and attorney in Sullivan City, Texas, lamented to Reuters. He figures he’d need at least ten cowboys to monitor his pastures during an outbreak. He has just two.
Wildlife, too, is at risk. Freddy Nieto, manager at El Sauz Ranch in South Texas, which caters to hunters as well as cattlemen, told Reuters, "This might be the worst biological outbreak that we’re facing in our lifetime." Infested wildlife are nearly impossible to treat; they simply vanish into the brush to die, threatening the region’s multi-billion-dollar hunting industry and the broader ecosystem.
Authorities in Mexico are also stepping up. Chiapas State Agriculture Secretary Marco Barba told Reuters that federal officials are reviewing the issue of illegal livestock crossings, which many believe have fueled the spread. "No country is immune," Barba said, noting that the state government has launched a campaign urging producers to check their herds and report any signs of screwworm.
But even with government action, ranchers are bracing for the worst. In May, West Texas rancher Warren Cude restocked his barn with wound spray and insecticides, placing them alongside jars of dead screwworms and old medicine canisters from the last outbreak. "We’re repeating history after 50 years. We didn’t learn from the first time and we let those facilities go and now we’re having to do everything again to combat something we eradicated 50 years ago," Cude told Reuters.
As cases continue to rise in Mexico and Central America, and with the U.S. ramping up its defenses, the race is on to prevent a disaster that would reverberate far beyond the ranches of Texas. The lessons of the past are clear, but the path forward is anything but easy. For now, ranchers, scientists, and government officials are holding their breath — and hoping history doesn’t repeat itself in the most painful way imaginable.
