Texas Faces Dangerous Parasite's Return After 60 Years: What's at Stake

The U.S. Department of Agriculture confirmed on June 3, 2026 that a serious flesh-eating parasite had been found in Texas for the first time since 1966. The parasite, called New World screwworm (NWS), was discovered in a cow in Zavala County, Texas, according to APHIS, which is the USDA's inspection agency. A second case was confirmed on June 5, as announced by APHIS. The discovery wasn't entirely unexpected: just days earlier, on May 29, Reuters reported that the parasite had been found in Mexico, only 31 miles from the Texas border, signaling the beginning of a northward spread.

What the Screwworm Does and Why This Matters

New World screwworm is a parasitic insect whose larvae eat the living tissue of warm-blooded animals. The female fly lays her eggs in any open wound—even a small cut or scrape—and the maggots that hatch dig deeper into the tissue, causing severe infection and death if left untreated.

What makes the screwworm particularly dangerous is how fast it reproduces. Under warm summer conditions in Texas, the fly can complete a full generation—from egg to adult—in roughly three weeks. This means populations can multiply exponentially during warm months, creating a potential outbreak that spreads rapidly.

The United States managed to eliminate this pest from the country by the mid-1960s using a technique called the sterile insect technique (SIT). The idea is surprisingly elegant: scientists breed millions of sterile male flies and release them into affected areas. When these sterile males mate with wild females, no offspring result, and the population collapses. Since then, a joint U.S.-Mexico-Central American program has used a production facility in Panama to release hundreds of millions of sterile flies weekly, keeping the parasite contained south of the Panama Canal. The appearance of the fly in Coahuila, Mexico, and now in Texas raises an urgent question: Has that barrier failed, or is this a temporary incursion that can be stopped?

How the Federal Government is Responding

The USDA moved fast. Upon confirming the Texas case, officials activated what they call the NWS Response Playbook—a pre-arranged set of actions and resources for exactly this scenario. The USDA's National Veterinary Stockpile—a warehouse of emergency supplies—immediately sent treatment medications to Texas. The most important ones are ivermectin and coumaphos, both proven wound treatments for infected animals, per APHIS.

USDA Secretary Rollins stated the agency believed it could contain the Texas case, as reported by Reuters on June 4, 2026. APHIS also clarified an important point: the screwworm poses no food safety risk. It only affects living tissue, so it cannot spread through beef or other meat products.

One piece of federal planning turned out to be especially timely. Back in March 2026, the USDA had already announced plans to build a new sterile fly production facility at Moore Air Base in Edinburg, Texas, according to APHIS. This facility was meant to reduce the U.S. government's dependence on the Panama facility and boost domestic production capacity. Now, with the June detection, this Edinburg facility has become critical to the actual response effort, not just a backup plan.

Texas Steps Up

Governor Greg Abbott declared a statewide disaster to prevent screwworm spread and protect livestock and wildlife, per the Governor's office. He also issued a second declaration specifically naming Zavala and Uvalde Counties as the initial disaster zone, according to a follow-on announcement.

Abbott also fast-tracked the Edinburg production facility and approved faster movement of sterile flies into Texas. Most notably, Texas formed a joint response team led by two state agencies: the Texas Parks and Wildlife Department (TPWD) and the Texas Animal Health Commission (TAHC). Including wildlife officials matters because screwworms don't only infect livestock. White-tailed deer, javelinas, and other wild animals in South Texas are highly vulnerable too. If the parasite spreads into wildlife populations, eradication becomes far more difficult—animals can't be corralled or treated like cattle.

State and federal officials urged people in the affected area to watch livestock and pets for signs of infection: irregular wounds, unusual odors, or visible maggots. Anyone suspicious should contact a veterinarian or state animal health officials immediately.

Why This Affects Prices and Markets

Reuters reported on June 4, 2026 that the screwworm confirmation caused cattle prices to spike—an immediate, if predictable, market reaction. South Texas sits in one of the densest cattle-raising regions in North America, and ranches there operate on thin profit margins with extensive grazing. They cannot afford the labor cost of inspecting animals daily for wounds as the response protocols require, nor can they tolerate movement restrictions that block seasonal sales and interstate shipments.

This has happened before, though most people today don't remember it. Before the sterile insect technique was developed, in the 1930s and 1940s, the screwworm caused hundreds of millions of dollars in losses across U.S. livestock every year—a staggering toll. The decades-long eradication campaign that followed was considered one of the greatest successes in applied insect control. Pushing the fly south of Panama required sustained teamwork between the U.S. and Mexico. If the parasite reestablishes a year-round population in Texas now, reversing it would likely take years of intensive sterile fly releases and would strain resources again.

The Critical Questions Ahead

The immediate puzzle is whether the two confirmed detections are isolated incidents—perhaps a few infected animals that crossed the border accidentally—or signs of an established, breeding population in Zavala County. That answer shapes everything: the scale of the response, how long it will take, and how much it will cost.

The USDA playbook calls for defining an infested zone, conducting aerial and ground releases of sterile flies, inspecting livestock before they move out of the zone, and setting up sentinel animals and traps to monitor the population. The fact that USDA is already accelerating sterile fly deliveries suggests officials are not waiting for population surveys to come in. They are deploying the sterile insect technique at scale now—a smart move given how quickly the fly reproduces.

One detail in the Texas response deserves attention: Uvalde County's inclusion alongside Zavala in the disaster declaration. The two counties share similar terrain and ranching operations, and Uvalde extends northward toward the Edwards Plateau—a region with one of the highest white-tailed deer densities in continental North America. If the screwworm takes hold in that deer population over the summer, eradication would stretch into years, and the state wildlife department's role would shift from supporting player to essential actor.

For agriculture trade, the looming question is whether other countries will restrict beef imports from Texas in response to the screwworm finding. The USDA's statement clarifying that screwworms don't pose a meat safety risk is partly a preemptive measure to prevent exactly that. Whether trading partners accept that reasoning will depend on their own rules and how quickly USDA can demonstrate containment is working.

The federal and state machinery mobilized as of June 6, 2026 is substantial. Whether it proves sufficient hinges on factors that won't be clear for weeks: the actual size of the fly population, wind and weather patterns, and how many wild animals carry the infection. The next two to three weeks, as surveillance data comes in from the infested zone, will tell us whether the 60-year reprieve is ending or whether Texas can slam the door shut once more.