New World Screwworm Confirmed in Texas for First Time Since 1966 — Federal and State Response Mobilizes

The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) confirmed on June 3, 2026 the detection of Cochliomyia hominivorax — New World screwworm (NWS) — in a bovine in Zavala County, Texas, according to APHIS. A second detection followed on June 5, after APHIS completed testing of additional suspect cases, confirmed in a subsequent APHIS announcement. The specific locus of the first confirmed case is La Pryor, in Zavala County — the first NWS confirmation in Texas since 1966, ending a six-decade absence from U.S. soil.

The detections did not arrive without warning. On May 29, 2026, Reuters reported that USDA had confirmed NWS in a six-month-old sheep in Mexico's Coahuila state, within 31 miles of the U.S. border — a signal that the fly's northward pressure had intensified well beyond its historical suppression corridor in Panama.

What NWS Is and Why the Timeline Matters

Cochliomyia hominivorax is an obligate parasite: its larvae feed exclusively on the living tissue of warm-blooded animals. Unlike the Old World screwworm (Chrysomya bezziana), which is an opportunistic secondary invader, NWS females deposit eggs in open wounds — however minor — and the resulting maggots excavate progressively deeper, causing severe myiasis that is fatal if untreated. The fly can complete a generation in roughly 21 days under warm conditions, making exponential population growth a realistic threat during a Texas summer.

The United States eradicated NWS domestically through a decades-long sterile insect technique (SIT) program, achieving continental U.S. freedom from the fly by the mid-1960s. A joint U.S.-Mexico-Central American SIT barrier has since held the population south of Panama, using a production facility in Pacora, Panama that releases hundreds of millions of sterile flies weekly. The reappearance in Coahuila — and now in Zavala County — raises immediate questions about whether that barrier has been breached or bypassed, and whether the fly has reestablished a breeding population north of the Rio Grande.

Federal Response: APHIS, USDA, and Pre-Positioned Infrastructure

APHIS activated the NWS Response Playbook immediately upon confirmation, coordinating containment and eradication operations with Texas state officials. USDA's National Veterinary Stockpile relocated NWS treatment supplies — primarily ivermectin and coumaphos wound-treatment products — to Texas to support producers operating within the infested zone, 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 confirmed that NWS poses no food safety risk — the parasite affects living tissue and does not persist in processed meat.

Critically, federal preparedness infrastructure was already partially in place before the June 3 detection. On March 9, 2026, USDA and the U.S. Army Corps of Engineers announced a construction contract with Mortenson Construction to build a new sterile fly production facility at Moore Air Base in Edinburg, Texas, according to APHIS. That facility is a central component of Secretary Rollins' five-prong NWS strategy, intended to expand USDA's domestic SIT capacity beyond exclusive dependence on the Panama operation. The Edinburg facility is now central to the active response, not merely a contingency asset.

Texas State Response: Disaster Declaration and Unified Command

Governor Greg Abbott issued a statewide disaster declaration framed around preventing NWS fly infestation and protecting livestock and wildlife, per the Governor's office. A subsequent declaration formally designated Zavala and Uvalde Counties as the initial disaster zone following the confirmed detection, according to a follow-on announcement.

Abbott also authorized the acceleration of sterile fly movement into Texas and approved construction of the new sterile screwworm production facility in Edinburg — aligning state authority with the federal contract already underway. A joint Texas NWS Response Team was stood up, co-led by the Texas Parks and Wildlife Department (TPWD) and the Texas Animal Health Commission (TAHC). The inclusion of TPWD alongside TAHC is operationally significant: NWS does not confine itself to livestock. White-tailed deer, javelinas, and other wildlife in the Edwards Plateau and South Texas brush country are highly susceptible hosts, and an uncontrolled epizootic in wildlife populations would complicate eradication considerably.

APHIS and USDA urged residents throughout the affected area to inspect livestock and pets for any signs of myiasis — irregular wounds, unusual odor, larvae visible at wound margins — and to contact veterinarians or state animal health officials immediately upon suspicion.

Market and Industry Implications

Reuters reported on June 4, 2026 that the NWS confirmation put ranchers on alert and contributed to a rally in cattle prices — a predictable near-term response given that the Texas-Mexico border region is among the densest cattle-producing corridors in North America. South Texas ranches operate on low-margin, extensive grazing models where daily livestock inspection at the scale required by NWS protocols is operationally burdensome. Movement restrictions within and around an infested zone carry direct revenue consequences for producers who rely on seasonal sales and interstate commerce.

We have seen this sequence before. In the 1930s and 1940s, before the SIT program existed, NWS caused estimated annual losses in the hundreds of millions of dollars across the U.S. livestock industry, and the human and wildlife toll was substantial. The eradication campaign that followed was one of the most successful applied entomological programs in history — but it took decades and sustained binational coordination to push the fly south of Panama. A re-establishment in Texas, even a limited one, would require years of SIT-intensive effort to reverse if the population gains a seasonal foothold.

What Comes Next

The immediate operational question is whether the two confirmed detections represent isolated introductions — perhaps via infested livestock movement across the border — or evidence of an established, reproducing population in Zavala County and surrounding terrain. That distinction determines the scale and duration of the response.

APHIS's playbook calls for a defined infested zone, aerial and ground sterile fly releases, mandatory wound inspections for livestock moving out of the zone, and intensive surveillance using sentinel animals and trapping networks. The acceleration of sterile fly delivery to Texas suggests USDA is not waiting for population estimates before deploying SIT at scale — a prudent posture given the fly's generation time.

Uvalde County's inclusion in the disaster declaration alongside Zavala warrants attention. The two counties share topography and livestock operations, and Uvalde's northern reaches extend toward the Edwards Plateau — a region whose white-tailed deer density is among the highest in the continental U.S. If NWS establishes in that deer population over summer, eradication timelines extend dramatically and the TPWD's role in the joint response team becomes load-bearing, not supplementary.

For agricultural trade, the key watch item is whether any U.S. trading partners impose movement restrictions on Texas livestock or beef products in response to the detection. USDA's food safety clarification — that NWS is not a meat safety concern — is partly aimed at preempting exactly that kind of market disruption. Whether trading partners accept that framing will depend on their own regulatory frameworks and the speed with which USDA can demonstrate active containment.

The federal-state apparatus mobilized as of June 6, 2026 is substantial. Whether it is sufficient depends on variables — fly population size, wind and weather patterns, the density of wildlife reservoirs — that will become clearer over the next two to three weeks as surveillance data accumulates from the infested zone.