A Dangerous Livestock Pest Returns to Texas for First Time in 60 Years

The U.S. Department of Agriculture confirmed on June 3, 2026 that a harmful parasite called the New World screwworm had been found in a cow in Zavala County, Texas — the first sighting in the state since 1966, according to APHIS. A second infected animal was confirmed two days later. The discovery was not a complete surprise: the USDA had already found the same pest in Mexico near the Texas border just a few weeks earlier, as reported by Reuters on May 29.

What This Pest Does and Why It Matters

The New World screwworm is a type of fly. Female flies lay eggs in open wounds on animals—even small cuts. The eggs hatch into larvae (maggots) that eat the living tissue beneath an animal's skin, creating deeper and deeper damage. If not treated, the infection kills the animal.

This is different from other types of fly maggots that invade already-infected or rotting tissue. Screwworms actively cause the damage themselves, and they do it fast. Under warm conditions like a Texas summer, these flies produce a new generation roughly every three weeks. That means a small problem can multiply into a large one very quickly.

The United States wiped out this pest across the country by the mid-1960s using a clever technique: scientists bred millions of male flies in laboratories, sterilized them, and released them into the wild. When sterile males mate with females, no offspring are produced. Repeat this enough times, and the wild population collapses. A similar program has kept the pest south of Panama ever since, releasing hundreds of millions of sterile flies every week from a facility in Panama.

The reappearance of screwworms in Texas after six decades raises a critical question: has the pest somehow broken through the barrier, or are these isolated cases? That answer will shape what happens next.

How the Federal Government Is Responding

Within days of the June 3 detection, the USDA activated its emergency response plan for screwworms. The agency moved medical supplies—mainly drugs to treat infested wounds—to Texas to help ranchers care for their animals, per APHIS.

The USDA Secretary said the agency believed it could contain the outbreak, according to Reuters on June 4. The USDA also made clear that this pest poses no risk to humans eating beef or other meat products—the screwworm only affects living animals, not the meat we purchase from stores.

The federal government had already begun preparing for exactly this scenario. In March 2026, the USDA and U.S. Army Corps of Engineers announced they were building a new facility in Edinburg, Texas that would produce millions of sterile flies domestically, per APHIS. Before the June detection, this facility was a backup plan. Now it is central to the active response.

Texas State Government Takes Action

Texas Governor Greg Abbott issued disaster declarations for Zavala and Uvalde Counties, freeing up state resources to fight the outbreak, per the Governor's office. He also authorized the state to speed up the arrival of sterile flies from the Panama facility and to support construction of the new Texas breeding facility.

A joint state response team was created, led by both the Texas Parks and Wildlife Department and the Texas Animal Health Commission. This structure matters: screwworms don't just infect livestock. White-tailed deer, javelinas, and wild animals throughout South Texas are also vulnerable. If the pest spreads into wildlife populations, it becomes far harder to eradicate.

The USDA and state officials asked ranchers and pet owners in the area to watch for signs of screwworm infection—unusual wounds, strange smells, or visible maggots—and to call a veterinarian immediately if they see anything suspicious.

What This Means for Ranchers and Beef Prices

The discovery pushed cattle prices up in the short term, per Reuters on June 4. South Texas is one of the densest cattle-raising regions in North America, and ranchers operating there work on thin profit margins. The protocols needed to stop screwworms—daily inspections, movement restrictions—are costly and logistically difficult for large operations.

The broader context here is that this exact scenario happened once before, decades ago, and cost the American livestock industry hundreds of millions of dollars annually until the pest was eliminated. A re-establishment in Texas would likely mean years of intensive effort to reverse—and potentially lasting disruption to regional ranching operations.

There is also the question of whether other countries will restrict imports of Texas beef or livestock out of concern about screwworms. The USDA has publicly stated that screwworms are not a food safety issue, partly to discourage such trade barriers. Whether other nations accept that argument will become clear as the weeks unfold.

What Happens Now

The critical unknown is whether these two detections are isolated incidents—perhaps a few animals that crossed the border already infected—or signs of an established population breeding in Zavala County. The answer determines whether the response is quick and localized or long and intensive.

The USDA's playbook calls for releasing sterile flies over a defined area, inspecting livestock before they leave the zone, and setting up traps and surveillance networks to monitor the pest population. The fact that federal officials are already deploying sterile flies at scale suggests they are not waiting to gather complete data before acting—a smart approach given how fast these flies reproduce.

The decision to include Uvalde County in the disaster declaration is worth noting. Uvalde borders Zavala and extends northward toward the Edwards Plateau, a region with one of the highest concentrations of white-tailed deer in the United States. If screwworms establish in that deer population over the coming months, the eradication effort becomes vastly more complicated and expensive.

The machinery activated as of early June 2026 is substantial and ready. Whether it proves sufficient will depend on variables—how many flies are actually out there, wind patterns, the density of wild animal populations—that will become clearer over the next two to three weeks as officials gather more information from the affected area.