Texas Ranchers Brace for Return of Flesh-Eating Screwworm Threat
A deadly livestock pest is advancing from Mexico toward Texas, threatening billions in losses and higher beef prices.
In the 1970s, screwworm infestations devastated U.S. cattle herds, forcing ranchers to either treat livestock manually or put down suffering animals. Now, ranchers like Kip Dove of Oakville, Texas, who vividly recalls the last outbreak, fear history is about to repeat itself.
The female screwworm fly lays eggs in any wound on a warm-blooded animal. The hatched larvae burrow into living flesh, feeding until untreated wounds become fatal. Even minor cuts from branding or ear tagging can turn into massive, maggot-filled injuries.
From 1972-1976, an outbreak across six states cost tens of millions to contain. Today, the USDA warns that a Texas infestation could cause up to $1.8 billion in economic damage.
Northward Advance from Mexico
Ranchers in central and southern Mexico are reporting infestations for the first time in a generation, and a sterile fly production plant in Panama is struggling to produce enough insects to keep the outbreak in check. The sterile fly technique-mating sterile males with wild females-was instrumental in the 20th-century eradication effort.
Cattle stand inside their corral on a ranch amid a growing outbreak of flesh-eating screwworms that threatens livestock and wildlife across the Chiapas state region, in Tapachula, Mexico July 4, 2025. REUTERS/Daniel Becerril
But the math is grim: 500 million sterile flies per week are needed, and the Panama facility can only produce 100 million. The USDA is now planning to reopen a long-shuttered Texas plant to increase output.
Economic and Ecological Risks
Beyond cattle, Texas' multibillion-dollar hunting industry is highly vulnerable, as wildlife such as deer and exotic game cannot be easily treated. Ranches that rely on hunting income could face devastating losses.
Freddy Nieto, manager of El Sauz Ranch in South Texas, warns this "might be the worst biological outbreak of our lifetime."
Flies settle on the wounded horn of a cow on a ranch in Tapachula, in southern Mexico, July 4, 2025. REUTERS/Daniel Becerril
The spread of screwworms could also push beef prices higher, adding to inflationary pressures already hitting consumers.
Labor Shortage Compounds Threat
Detecting and treating screwworm infestations requires daily inspection of every animal-a daunting task in rugged Texas terrain. Many ranches lack the skilled cowhands needed for such intensive monitoring.
A worker with Honduras' Secretary of Agriculture and Livestock shows the navel of a cow treated to eliminate the larvae of the screwworm fly, at a cattle ranch in Apacilagua, Honduras, May 16, 2025. REUTERS/Fredy Rodriguez
Isaac Sulemana, a rancher in Sullivan City, Texas, estimates he'd need five times his current staff to keep up with inspections during an outbreak.
Larva of the screwworm fly is extracted from a bull's flesh at an inspection center of Honduras' Secretary of Agriculture and Livestock, in Valle de Jamastran, Honduras, May 21, 2025. REUTERS/Fredy Rodriguez
Ranchers Prepare for Battle
The USDA has halted cattle imports from Mexico and deployed inspectors along the border. Ranchers are stockpiling insecticides, installing traps, and revisiting old eradication protocols.
Warren Cude, a third-generation rancher, has restocked his barn with wound sprays and insecticides, recalling the eradication campaign of the 1970s. "We're repeating history after 50 years," he said. "We didn't learn from the first time."
