New World Screwworm Reaches Texas

Estimated Time to Read: 14 minutes

Texas is no longer dealing with a distant New World Screwworm (NWS) threat. On June 3, the U.S. Department of Agriculture (USDA) confirmed the presence of NWS in cattle in Zavala County, Texas, marking the first confirmed detection in the United States after months of warnings, surveillance, border restrictions, sterile fly dispersal efforts, and growing concern across the agriculture community.

The affected animal was a three-week-old calf, and larvae were identified in the calf’s umbilical area. As of the federal announcement, USDA said there had been no further detections. That detail matters because the central question now is whether this remains an isolated case or becomes evidence of a broader, self-sustaining population.

New World screwworm is a parasitic fly that affects livestock, pets, wildlife, and, less commonly, people and birds. Its larvae feed on the living flesh of warm-blooded animals, causing severe injury and potentially death if left untreated. While the threat to animal health and agriculture is serious, USDA has emphasized that NWS is not a food safety concern and does not infest meat, fruits, vegetables, or other food sources.

For Texas, this discovery represents a major escalation from prevention to containment. It also validates concerns raised over the last year by state officials, agricultural leaders, and lawmakers who warned that the pest’s northward movement through Mexico posed a direct threat to Texas ranchers, rural communities, wildlife, and the broader food supply chain.

What Happened With the New World Screwworm Case in Texas

The confirmed NWS case was found in Zavala County in South Texas. USDA tested the sample at its National Veterinary Services Laboratories in Ames, Iowa, and confirmed the infestation on June 3. The sample came from La Pryor, and the infested animal was a three-week-old calf.

This discovery followed a long period of escalating concern. New World screwworm had already been moving northward through Central America and Mexico, leading USDA to close southern livestock ports of entry, expand surveillance, shift sterile fly dispersal closer to the U.S.-Mexico border, and begin building out new sterile fly capacity in Texas.

In practical terms, the June 3 confirmation changed the posture of the response. Texas is no longer preparing for the possibility of an NWS incursion. Texas is now responding to one.

The distinction between an isolated case and an established outbreak remains important. USDA’s own response framework treats NWS establishment as the presence of a self-sustaining and reproducing wild fly population. An isolated case, by contrast, may be contained to the initial finding and may not necessarily indicate a wider outbreak. The immediate response is therefore focused on determining the scope of the threat, preventing spread, and eliminating any possibility of reproduction in the affected area.

The stakes are substantial. Reuters reported that the discovery threatens a U.S. cattle herd already at its lowest level in 75 years, with beef prices already at record highs. The same report noted that traders and market participants have been sensitive to the threat of NWS because a broader outbreak could further tighten cattle supplies, disrupt trade flows, reduce confidence in the beef market, and increase production costs for ranchers.

That does not mean consumers should panic. It does mean the economic consequences of a failed response could extend far beyond the infected animal or the immediate quarantine zone. A single confirmed case in South Texas is enough to raise questions about cattle movement, trade, market uncertainty, producer costs, and the adequacy of federal preparedness.

The Timeline: From Warning Signs to Texas Confirmation

Texas Policy Research (TPR) began writing about the NWS threat in July 2025, when the issue was still largely framed as a looming agricultural and border biosecurity concern. At that time, the parasite had not been confirmed in the United States, but the threat was moving closer through Mexico and Central America.

A brief timeline helps show how Texas got here:

• May 11, 2025: USDA suspended live cattle, horse, and bison imports through southern border ports of entry after New World screwworm detections in Mexico raised concerns about northward spread.
• June 18, 2025: USDA Secretary Brooke Rollins announced an $8.5 million sterile fly dispersal facility in South Texas and a broader five-pronged plan to detect, control, and eliminate New World screwworm.
• September 17, 2025: Texas Governor Greg Abbott (R) signed House Concurrent Resolution 13 (HCR 13), urging the federal government to work with Mexico on a response plan, expedite construction of the planned screwworm control facility at Moore Air Force Base in Texas, partner with Texas A&M AgriLife for research space, and speed approval of treatments and pesticides through the FDA and EPA.
• September 22, 2025: USDA announced that Mexico had confirmed a New World screwworm case in Nuevo León. USDA urged southern border residents to check pets and livestock for draining or enlarging wounds, signs of discomfort, larvae, eggs around body openings, or infestations around the navel of newborn animals.
• January 30, 2026: USDA announced that it was shifting its 100 million per week sterile fly dispersal efforts to defend the U.S. border. The new dispersal area included operations approximately 50 miles into Texas along the U.S.-Mexico border.
• March 9, 2026: USDA and the U.S. Army Corps of Engineers announced a construction contract for a new sterile fly production facility at Moore Air Base in Edinburg, Texas. USDA said the facility would become the only U.S.-based sterile fly production facility and was expected to reach an initial goal of producing 100 million sterile flies per week by November 2027, with a longer-term goal of 300 million per week.
• April 20, 2026: Texas Agriculture Commissioner Sid Miller (R) warned that a confirmed case in Nuevo León, approximately 62 miles from the Texas border, put Texas “squarely in the crosshairs.” He called for expanded surveillance, tighter border coordination, and full deployment of available resources.
• May 1, 2026: Commissioner Miller warned again after the first confirmed detection in Coahuila, Mexico, roughly 119 miles from the Texas border. Miller called the detection a “serious wake-up call” and said Texas was “on the front lines.”
• June 3, 2026: USDA confirmed NWS in a calf in Zavala County, Texas. That confirmation triggered the current containment and eradication response.

This timeline shows that the Texas case was not a surprise in the broader policy sense. The warning signs had been building for months.

What the New World Screwworm Response Is in Texas

USDA and Texas officials are now implementing an active containment and eradication response. USDA has said the response includes forming a unified Incident Command Team with the Texas Animal Health Commission (TAHC), deploying response personnel to the area, establishing a 20-kilometer infested zone around the detection, implementing quarantines and movement controls, increasing trapping, conducting wildlife surveillance, and expediting sterile fly releases.

The Texas Animal Health Commission has identified the affected area as Infested Zone 01. Under TAHC’s movement guidance, warm-blooded animals within the zone may not move out of the zone without prior authorization. In general, animals must be inspected, treated as required, and issued a permit or certificate for movement by a TAHC representative before moving outside the infested zone.

USDA’s Response Playbook explains why the zone matters. The playbook calls for the immediate establishment of a minimum 20-kilometer infested zone and a surrounding adjacent surveillance zone after certain NWS detections. The purpose is to coordinate response activities, control animal movement, conduct surveillance, and determine whether the pest has become established.

The response also relies heavily on the sterile insect technique. This method was used to eradicate NWS from the United States decades ago. Female NWS flies mate only once. When they mate with sterile males, their eggs do not hatch. When paired with surveillance, movement controls, animal inspections, and public outreach, sterile fly release can break the reproductive cycle of the pest.

USDA has said it is expediting targeted sterile fly releases by deploying ground release chambers in the area, in addition to sterile flies already being released aerially. The purpose is to prevent any reproducing population from taking hold in Texas.

The goal should be clear: move fast, contain the pest, protect livestock and wildlife, preserve continuity of business where possible, and avoid unnecessary disruption to ranchers and rural communities.

Responses From Federal and State Officials

USDA has framed the response as urgent and national in scope. Dudley Hoskins, USDA Under Secretary for Marketing and Regulatory Programs, said, “Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action.” He also said, “The United States has defeated this pest before, and we will do it again.”

USDA Secretary Brooke Rollins used similar language when USDA announced its broader response strategy in 2025. “The United States has defeated NWS before, and we will do it again,” Rollins said. “We do not take lightly the threat NWS poses to our livestock industry, our economy, and our food supply chain.”

Texas Agriculture Commissioner Sid Miller (R) has taken a more critical tone toward the federal response. On June 3, after the first suspected Texas case was reported, Miller said, “For months, the screwworm has advanced rapidly through Mexico in spite of the USDA’s existing gameplan.” He added that even though billions of sterile flies had been dispersed by USDA, the pest had advanced more than 1,100 miles from southern Mexico to Texas, and that “the consequences of that decision are now staring us in the face.”

Miller also called for deployment of the Screwworm Adult Suppression System, or SWASS, arguing that USDA already had a proven tool available. “SWASS was developed by USDA, tested by USDA, and successfully deployed by USDA to eradicate screwworm in Mexico and Texas when it last appeared,” Miller said. “USDA already owns the playbook; the only question is whether USDA will use it before this situation gets worse.”

Gov. Greg Abbott’s (R) office emphasized state coordination and readiness. In a statement from spokesman Andrew Mahaleris, the governor’s office said, “The Governor’s New World Screwworm Response Team, composed of the Texas Animal Health Commission and the Texas Parks and Wildlife Department, in close coordination with the USDA and other federal partners, is leading the state’s NWS response with enhanced tools and personnel deployed to deter any threat.”

The governor’s office also said that if the case was confirmed positive, the response team would “immediately establish an incident response post, expand fly trapping and surveillance efforts, and restrict animal movement to prevent further spread of the pest.” The statement added that targeted releases of sterile New World screwworm flies would be expedited “to eliminate any reproducing populations in the area,” and that Abbott would use “all necessary resources to eradicate this pest and protect Texas land, livestock, and wildlife.”

Taken together, the quotes show three overlapping messages. USDA is emphasizing containment and confidence. The Texas Department of Agriculture is pressing for more aggressive tools and federal accountability. The governor’s office is presenting Texas’ role as coordinated, operational, and ready to escalate.

New World Screwworm Economic Stakes for Texas Agriculture

The economic concern is not limited to the infected animal or even the immediate quarantine zone. New World screwworm threatens the broader livestock economy because containment depends on fast detection, animal inspections, movement controls, treatment availability, sterile fly deployment, and confidence that the pest is not spreading.

For Texas ranchers, even a limited detection can create immediate uncertainty. Producers may need to navigate inspection requirements, movement permits, treatment protocols, added labor costs, and the possibility of temporary disruptions at markets, sale barns, or transport routes. Those costs are especially burdensome for smaller producers who may not have the same flexibility or resources as larger operations.

The timing also matters. Cattle markets have already been under pressure from tight supply conditions, high input costs, drought recovery, and elevated consumer beef prices. A broader NWS outbreak could compound those existing pressures by increasing production costs, creating uncertainty around cattle movement, and undermining market confidence.

That is why the response must be both aggressive and carefully targeted. A slow response risks allowing the pest to spread, which would create far greater economic damage. But an overly broad or poorly communicated response could also harm producers by creating confusion, unnecessary delays, and avoidable market disruption.

The right balance is a rapid, transparent, science-based response that protects livestock and wildlife while preserving continuity of business wherever possible. In practice, that means clear quarantine boundaries, timely updates, fast permitting, sufficient personnel, accessible treatment options, and a defined process for lifting restrictions once the threat is contained.

New World Screwworm Policy Implications for Texas Agriculture

The confirmation of NWS in Texas raises several policy questions that should remain front and center once the immediate response is underway. First, border biosecurity must be treated as a core agricultural protection function. The pest’s movement through Central America and Mexico, followed by livestock import restrictions and sterile fly deployments near the border, shows that Texas cannot afford a reactive posture when foreign animal diseases threaten the state’s livestock economy.

Second, sterile fly capacity is now a strategic concern. The sterile insect technique remains the central tool for eradication, but the timeline for expanded domestic production at Moore Air Base shows why Texas and federal officials should treat sterile fly infrastructure as agricultural security infrastructure. A state as central to cattle production as Texas should not be left waiting on limited capacity during an active threat.

Third, emergency response must be fast, targeted, transparent, and temporary. Quarantines, movement restrictions, inspections, and treatment requirements may be necessary, but they should be tied to clear risk zones, updated as surveillance data changes, and lifted once the threat is contained. Ranchers, landowners, sale barns, veterinarians, and transporters need clear rules, quick permitting, and regular public updates.

Finally, policymakers should evaluate what worked and what failed after the immediate emergency is stabilized. Texas lawmakers had already warned the federal government through HCR 13, and state agriculture officials had repeatedly sounded the alarm. Any after-action review should focus on federal readiness, cross-border coordination, treatment approvals, sterile fly capacity, and whether Texas had the tools it needed before the pest reached U.S. soil.

The goal should be aggressive eradication without permanent mission creep. Protecting livestock, wildlife, the food supply, and agricultural commerce is a legitimate public responsibility, but the response should remain disciplined, transparent, and limited to the emergency at hand.

The Path Forward

The confirmation of NWS in Texas is a serious moment for agriculture, rural communities, wildlife management, border biosecurity, and consumers already facing high beef prices. It also confirms that the warnings raised over the last year were not theoretical. The threat has reached Texas.

The immediate priority should be containment and eradication. That means rapid surveillance, targeted quarantines, sterile fly deployment, animal inspections, wildlife monitoring, and clear public communication. It also means ensuring that producers understand the rules and that any restrictions on movement are narrow, evidence-based, and temporary.

Texas had already sounded the alarm through legislative action, state agency coordination, and repeated warnings from agricultural officials. Now that the pest has been confirmed inside the United States, state and federal leaders must move quickly to prevent a single confirmed case from becoming a broader outbreak.

New World screwworm has been defeated in the United States before. It can be defeated again. But doing so will require urgency, coordination, transparency, and a willingness to evaluate what worked, what failed, and what must change before the next agricultural threat reaches Texas.

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