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New World screwworm · threat-tracking system
U.S. detections: 52 confirmed as of September 29, 2026. Up 3 since September 15, 2026. 2 new reports in the last 48 hours.
As of Aug 2026, 45 New World screwworm detections have been confirmed in the United States, 5 of them currently active (all in Texas (Terrell, Sutton, Starr, Brewster ×2)). Dated figure and history
Independent trackerThis is an independent public-interest tracker. It is not an official USDA, TAHC, or COPEG website. For suspected cases, contact your veterinarian and official animal-health authorities immediately.
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Confirmed in Zavala County, TX
Zavala County, TX · …
Infested Zone 01 · Zavala & Uvalde Co.
COPEG · Darién Gap, Panama
No U.S. cases. International watch only.
Cases in neighboring countries approaching the U.S. border.
Cases confirmed in Mexico border states; heightened surveillance.
Confirmed U.S. detections, active movement restrictions, sterile-fly response active.
Triggers currently met: confirmed U.S. detection in Zavala County, TX (Jun 2026); sterile-fly response active via COPEG. This places the tracker at CRITICAL. Threat level is The Stovall Report's independent assessment, not an official government alert level.
Zones:Brewster, Crockett, Culberson, Edwards, El Paso, Hudspeth, Jeff Davis, Pecos, Presidio, Reeves, Schleicher, Starr, Sutton, Terrell, Val Verde, Zapata
Latest order 10/31:Executive Director Order - Culberson and Hudspeth Counties
≈ = approximate / illustrative
New World screwworm was detected in Mexico near the U.S. border, raising concern about a northward spread of a parasite the U.S. eradicated in 1982.
Confirmed cases across southern Mexico and Central America underscored that the parasite was moving north toward established livestock regions.
USDA APHIS activated an emergency response and expanded the sterile insect technique barrier — the same approach that eradicated screwworm from the U.S. decades ago.
Gov. Greg Abbott issued a New World screwworm disaster proclamation, directing state agencies to prepare and respond as the highest-risk U.S. state.
USDA APHIS confirmed New World screwworm in a three-week-old calf with an umbilical-area infestation near La Pryor, Zavala County, TX — verified by the National Veterinary Services Laboratories in Ames, Iowa. It is the first U.S. detection since the 1982 eradication. TAHC issued an Executive Director Order restricting animal movement in Zavala and Uvalde counties the same day.
Animal-health officials began targeted sterile-fly releases and stood up "Infested Zone 01" (Zavala & Uvalde counties), expediting the sterile insect technique alongside enhanced surveillance and movement restrictions to eliminate any reproducing population.
USDA APHIS confirmed a second detection — a roughly one-month-old calf about 5.6 miles from the first case, inside the existing infested zone. TAHC issued a Modified Executive Director Order tightening movement controls; Gov. Abbott expanded the state disaster declaration.
USDA APHIS confirmed three more detections, bringing the U.S. total to five: a calf in La Salle County and a goat in Gillespie County, Texas, plus a dog in Lea County, New Mexico — the first U.S. case outside Texas. Mexico halted most U.S. animal imports, including pet dogs, in response.
The FDA issued an Emergency Use Authorization for an ivermectin oral solution for the short-term prevention of New World screwworm infestation in horses, administered at the time of initial wound care. It is part of a widening set of federal countermeasures as detections continue in Texas.
USDA announced that the Douglas, Arizona port would reopen to cattle trade on August 24, 2026 — the first step in a phased reopening of southern livestock ports closed during the screwworm response, with Santa Teresa and Columbus, New Mexico to follow pending a risk review. Every animal is inspected for New World screwworm on entry, and the timeline stays contingent on Mexico meeting joint action-plan milestones.
Agriculture Secretary Brooke Rollins announced a $25 million commitment for a new sterile-fly dispersal facility in Douglas, Arizona during a visit to the Douglas port of entry. It would be only the second such facility in the U.S. (the other is in southern Texas) and would strengthen response capacity along the Southwest border as the Douglas port prepares to reopen to cattle trade on August 24.
Texas designated a new infested zone in Terrell County after New World screwworm was confirmed in a sheep, tightening movement controls there. Since June, U.S. detections have totaled 45, with only five still active — all in Texas (Terrell, Sutton, Starr, and Brewster). Movement restrictions now touch parts of 23 Texas counties.
The first U.S. detection since the 1982 eradication was confirmed on June 3, 2026 in a calf in Zavala County, Texas. Since then USDA APHIS has logged 45 confirmed U.S. detections — 44 in Texas and one dog in Lea County, New Mexico. As of August 2026, only five cases remain active, all in Texas: Terrell, Sutton, Starr, and Brewster (two) counties.
Movement restrictions now cover parts of 23 Texas counties, from the Rio Grande Valley through West Texas and the Hill Country. The five currently active cases are in Terrell, Sutton, Starr, and Brewster (two) counties. The only U.S. detection outside Texas remains a dog in Lea County, New Mexico. This follows the parasite's northward spread from Central America and Mexico through 2024–2025.
USDA APHIS activated an emergency response and expanded its sterile insect technique (SIT) barrier to slow and push back the parasite's northward spread.
Texas is considered the highest-risk U.S. state because of its long border with Mexico and its large livestock population.
TAHC first designated "Infested Zone 01" across Zavala and Uvalde counties after the June 2026 detections. As the footprint spread, additional infested zones were added — most recently in Terrell County in early August 2026, after New World screwworm was confirmed in a sheep. Warm-blooded animals cannot leave an infested zone without TAHC authorization and inspection. Gov. Greg Abbott's New World screwworm disaster proclamation remains in effect.
On July 24, 2026, USDA announced a phased reopening of southern livestock ports. The Douglas, Arizona port reopens to cattle trade on August 24, 2026, with Santa Teresa and Columbus, New Mexico to follow pending a risk review. Every animal entering the U.S. is inspected for New World screwworm, and USDA says the timeline stays contingent on Mexico meeting joint action-plan milestones.
Screwworm primarily affects livestock and other warm-blooded animals. Human infestation (myiasis) is possible but rare, and is treatable when caught early.
Screwworm is fought with the sterile insect technique: vast numbers of lab-raised, sterilized male flies are released so wild females mate without producing offspring, collapsing the population over time. The barrier protecting the U.S. depends on how many sterile flies can be produced and dispersed each week.
The U.S. maintains a permanent biological barrier in Panama's Darién Gap through COPEG — the Commission for the Eradication and Prevention of Screwworm, jointly run by the U.S. and Panama — releasing sterile flies to keep the parasite from moving north.
In response to the 2024–2025 northward spread, USDA expanded its SIT operations, releasing lab-raised, sterilized male flies further north to reinforce the barrier.
Sterile males are released in overwhelming numbers. Because females typically mate once, matings with sterile males produce no larvae — sustained releases drive the wild population down and eventually out.
The New World screwworm (Cochliomyia hominivorax) is a parasitic fly whose larvae (maggots) feed on the living tissue of warm-blooded animals. Female flies lay eggs at the edge of a wound or a natural body opening; the hatching larvae burrow into living flesh, creating a wound that grows progressively larger and draws still more flies. It affects all warm-blooded animals — cattle, horses, sheep, goats, deer, dogs, and, rarely, people. The United States eradicated it decades ago, which is why any renewed threat is treated as a serious event.
Texas runs the largest cattle herd in the country, and screwworm threatens cattle, sheep, goats, horses, wildlife such as deer, and household pets. For ranchers it can mean sick animals, costly treatment, and movement restrictions on livestock; for pet owners it means any open wound on an outdoor animal needs closer attention if the parasite reaches the U.S. Early detection and prompt reporting are what keep a few cases from becoming a regional infestation.
An enlarging wound that gets worse over time rather than healing the way an ordinary cut would — a hallmark of screwworm infestation.
Infested wounds give off a distinctive foul odor and contain visible maggots feeding in the living tissue.
Screwworm larvae burrow head-down into living tissue and are often partly buried, with spiny bands around the body. Look in and around wounds.
Check the nose, ears, eyes, and genitalia — and especially the navel of newborn animals, a common site of infestation.
Every fact in this dossier is tied to a named source with a date. Map zones are approximate and illustrative — drawn from the regions named in the sourced facts, not survey data. This page is not a substitute for guidance from a veterinarian or animal-health official. See SCREWWORM_SOURCES.md for the full sourcing record.
Daily practices that catch a case early and keep flies from reproducing.
General guidance only — not a substitute for direction from a veterinarian or animal-health official. For suspected cases, contact the TAHC (1-800-550-8242) or USDA hotline (1-800-872-7367) immediately.
Screwworm isn't just a cattle problem — any outdoor animal with an open wound is at risk.
General guidance only — not a substitute for direction from a veterinarian or animal-health official. For suspected cases, contact the TAHC (1-800-550-8242) or USDA hotline (1-800-872-7367) immediately.
Front-line detection and reporting for suspected myiasis.
General guidance only — not a substitute for direction from a veterinarian or animal-health official. For suspected cases, contact the TAHC (1-800-550-8242) or USDA hotline (1-800-872-7367) immediately.
How to cover this accurately and where the sourced facts live.
General guidance only — not a substitute for direction from a veterinarian or animal-health official. For suspected cases, contact the TAHC (1-800-550-8242) or USDA hotline (1-800-872-7367) immediately.
Use this form to report a suspected New World screwworm case. Reports are logged for review — they do not replace contacting a veterinarian or the USDA/TAHC hotline for urgent or confirmed cases. Only your name and a location description are required; the rest helps responders.
This form is reviewed by The Stovall Report for public tracking. It does NOT notify USDA, TAHC, or emergency responders. For an urgent or suspected case, call the official hotlines below and your veterinarian first.
Reports are reviewed by The Stovall Report and may be used for public tracking with personal details removed. This does NOT notify USDA, TAHC, or emergency responders.
Submitting is your consent for us to store any photos and the location (GPS coordinates or description) you choose to include, and to publish a de-identified version for tracking. Photos and precise location are optional — include only what you're comfortable sharing.
Reports are retained for the duration of the screwworm tracking effort. You can ask us to remove your report or contact details at any time.
You'll get a reference number for your records. A Stovall Report reviewer checks the report and may add a de-identified marker to the public tracker. We do not dispatch responders — official follow-up only happens if you contact the hotlines and your veterinarian directly.
Add your name to call for an urgent, coordinated response to the New World screwworm threat in Texas. Your signature helps demonstrate the scale of public concern to officials and lawmakers.
This is a public advocacy petition by The Stovall Report, not an official government form.