New World Screwworm Statistics in US 2026 | Cases, Treatments & Key Facts

New World Screwworm in the US 2026

The New World screwworm (NWS) — a parasitic fly whose larvae burrow into and feed on the living flesh of warm-blooded animals — returned to the United States on June 3, 2026, for the first time in nearly 60 years. USDA-APHIS confirmed the first case that day: a 3-week-old calf in Zavala County, Texas, near La Pryor in South Texas, with larvae in the animal’s umbilical area. By June 22, 2026 — yesterday — 15 cases had been confirmed across two US states: 14 in Texas spanning multiple counties and 1 in New Mexico’s Lea County, in cattle, goats, sheep, and dogs. The US had last recorded a domestic animal case in 1986, following a 24-year eradication campaign that released over 96 billion sterile flies before the continental US was declared free in 1966. USDA’s own models had projected NWS would cross the border in 2025 — the first confirmed case arriving in June 2026 reflects both the proximity of that estimate and the effectiveness of USDA’s pre-emptive containment work in Mexico and Central America.

The outbreak is the culmination of a three-year northward march that began when Panama and Costa Rica identified NWS in 2023, breaking the long-stable Darién Gap containment barrier. By November 2024, NWS had reached livestock in Chiapas, Mexico, triggering US livestock import suspensions from Mexico in May 2025 and USDA investments of $750 million toward a South Texas sterile fly facility and up to $100 million for new control research. The CDC has confirmed no locally acquired human US infestations, though one travel-related human case was confirmed in August 2025 in a person who visited El Salvador. In Mexico and Central America, over 185,000 cumulative animal cases and 2,100+ human cases have been recorded since 2023.

Interesting Facts: New World Screwworm in the US 2026

Source: USDA APHIS press releases June 3, 8, 9, 2026 (aphis.usda.gov); CDC New World Screwworm Situation Summary (cdc.gov, updated June 2026); Texas Animal Health Commission (tahc.texas.gov, updated June 22, 2026); FOX9 June 22, 2026; CNN June 3, 2026; American Farm Bureau Federation Market Intel, June 2026; Drovers Magazine, June 2026; FDA animal drug authorizations (fda.gov)

The 15 confirmed US cases as of June 22, 2026 represent a rapidly evolving outbreak — the country went from zero to 15 confirmed cases in fewer than three weeks. What makes the data more alarming is the epidemiology of NWS itself: the fly is not contagious in the way that a bacterial or viral disease spreads between animals. Instead, each new case represents a fresh fly laying eggs in an unrelated wound on a different animal. The fact that cases have appeared across multiple Texas counties — spanning a wide geographic band from South Texas toward the Hill Country — suggests wild fly activity is already distributed across a substantial area, not confined to a single point of introduction. USDA APHIS confirmed that the Edwards County cases found on June 22 were “within an area already under surveillance and were not unexpected” — a statement that acknowledges the containment perimeter is active but the fly population is still moving.

The no locally acquired US human case is the most reassuring finding, but 2,100+ human cases in Mexico and Central America confirm that human infestation is real in areas with active fly circulation. The CDC notes risk is currently localised to areas where NWS flies are present — parts of South Texas and the immediate border region. For people with open wounds or skin lesions, the guidance is direct: keep all wounds covered, wear protective clothing, use permethrin-treated clothing, and seek immediate medical care if larvae are visible.

US New World Screwworm Case Timeline in 2026

US NWS Confirmed Case Progression (June 2026, USDA APHIS)
==========================================================
June 3   |█                                         | 1 case (Zavala County, TX — calf)
June 8   |████                                      | 4 cases (+calf La Salle TX, +dog Andrews TX, +1 more)
June 9   |██████                                    | 6 cases (+calf La Salle County TX)
June 9+  |████████████████                          | Additional cases across Hill Country
June 22  |███████████████████████████████           | 15 total (14 TX, 1 NM)
------------------------------------------------------------
Source: USDA APHIS press releases; FOX9 June 22, 2026; dvm360 live tracker

Source: USDA APHIS press releases June 3, 8, 9, 2026; Texas Animal Health Commission June 22, 2026; FOX9 New World Screwworm Texas June 22 update; dvm360 live NWS tracking page

The case progression from 1 on June 3 to 15 on June 22 — a 20-day window — describes a fly population that had already established local presence before the first detection was confirmed. NWS detection in the US relies on passive surveillance: producers, veterinarians, and wildlife officers visually identifying suspicious wounds and reporting them. The fact that cases appeared near-simultaneously in multiple Texas counties, and crossed into New Mexico within the same three-week window, strongly suggests the fly population had been present for some time before June 3 — consistent with USDA’s own modelling, which had predicted NWS would enter the US in 2025. The June 3 detection was the first confirmed case, not necessarily the first fly.

The 14 quarantined Texas counties span from Webb and Zavala on the Mexican border northward through the Hill Country to Tom Green and Coke. All warm-blooded animals within the infested zone require prior TAHC authorisation before moving out, with movement certificates listing treatment details and official animal IDs. For the Texas cattle industry — already under strain from record prices driven by tight national inventory — this administrative burden adds cost at precisely the wrong time.

New World Screwworm Spread: From Panama to the US in 2026

NWS Northward Spread Timeline (2006–2026)
==========================================
2006        |                                    | Panama declared NWS-free
2023        |████                                | Outbreak begins Panama/Costa Rica
2024        |████████████████████                | All Central American countries affected
Nov 2024    |████████████████████████████████    | NWS detected Chiapas, Mexico
2025        |█████████████████████████████████   | Rapid spread through Mexico northward
May 2025    |█████████████████████████████████████| US halts Mexican livestock imports
Jun 3, 2026 |████████████████████████████████████████| FIRST US CASE confirmed
Jun 22, 2026|████████████████████████████████████████████| 15 US cases (TX + NM)
------------------------------------------------------------
Mexico + C. America: 185,000+ animal cases; 2,100+ human cases
Source: USDA APHIS; CDC; Texas Animal Health Commission; COPEG

Source: CDC NWS Situation Summary (updated June 2026); USDA APHIS agency announcements; Drovers Magazine NWS History and Resurgence; Texas Animal Health Commission; COPEG (Panama-United States Commission for Eradication and Prevention of Screwworm)

The 2023 Panama breach was the critical failure point. For decades, COPEG’s Panama facility — capable of 100 million sterile flies per week — maintained a Darién Gap barrier preventing northward spread. When it broke, the outbreak cascaded through all six Central American countries within roughly two years, accumulating 185,000+ animal and 2,100+ human cases before reaching Mexico in November 2024. Panama to the US border in approximately 30 months reflects the fly’s reproductive capacity and the practical limits of multi-country containment infrastructure.

The US-Mexico livestock import closure — first enacted November 22, 2024, reinstated May 11, 2025, and still in effect — represents one of the most significant agricultural trade disruptions between the two countries in years. Live cattle imports from Mexico were entirely halted, compounding pressure in a market already at historically low herd numbers. The American Farm Bureau Federation noted record cattle prices in 2026 are a sign of market strain rather than success, and NWS arrived at precisely the moment the industry could least absorb additional disruption.

New World Screwworm Symptoms and Clinical Signs in 2026

Clinical Progression of NWS Infestation (CDC / USDA / TAHC)
=============================================================
Day 1–2   |████                                    | Eggs laid in wound; larvae hatch
Day 2–5   |████████████████████████████████████████| Larvae burrow into living tissue; wound enlarges
Day 5–7   |████████████████████████████████████████████████████| Deep tissue damage; foul odour
Day 7+    |█████████████████████████████████████████████████████| Death if untreated (TAHC)
------------------------------------------------------------
Entry points: wounds, navel (newborns), nose, ears, genitalia, any skin break

Source: CDC New World Screwworm situation summary and prevention guidance (cdc.gov); USDA APHIS June 3, 2026 press release; Texas Animal Health Commission (tahc.texas.gov); dvm360 clinical guidance; CNN June 3, 2026

Female NWS flies are attracted to any fresh wound — including a scratch, tick bite, or insect bite — and lay 150–500 eggs at the wound margin. Eggs hatch in 12–21 hours and larvae immediately burrow headfirst into living tissue. Unlike housefly larvae that feed on dead material, NWS larvae require living tissue — making an enlarging, foul-smelling, maggot-containing wound in a live animal an NWS case until proven otherwise. TAHC confirmed untreated animals can die within one week, leaving almost no room for delayed diagnosis.

The first US case in a newborn calf’s umbilical area is diagnostically typical — the navel is a common NWS entry site, remaining moist and exposed for days after birth. Producers in the quarantine zone are advised to delay elective wound-creating procedures — dehorning, castration, branding — and to treat all wounds immediately with approved insecticides. The TAHC hotline 1-800-550-8242 handles livestock reporting with a mandatory 24-hour reporting window from first suspicion.

New World Screwworm Treatments and FDA Authorizations in 2026

FDA-Authorized NWS Treatments by Category (2025–2026)
======================================================
Livestock (cattle, sheep, goats, swine):
  Doramectin (Dectomax-CA1)      |████████████████████| Prevention + treatment (21-day reinfest. protection)
  Ivermectin (Ivomec EUA)        |████████████████████| Prevention in cattle (EUA Feb 2026)
  Coumaphos/propoxur (Negasunt)  |████████████████████| Treatment + prevention (USDA-restricted supply)
  Permethrin (Catron IV)         |████████████████████| Kills flies and maggots; OTC via EPA approval

Companion animals (dogs/cats):
  Lotilaner (Credelio) EUA       |████████████████████| Larvae treatment
  Credelio Quattro-CA1           |████████████████████| Conditional FDA approval (dogs)
  Nitenpyram (generic OTC)       |████████████████████| Kills larvae within hours; 1.4mg + 57mg tablets

Wild/exotic animals:
  F10 Antiseptic Wound Spray     |████████████████████| Prevention + treatment (EUA)
  Negasunt Powder                |████████████████████| EUA — via USDA only
------------------------------------------------------------
Source: FDA (fda.gov); dvm360 June 2026; Drovers; Zoetis US

Source: FDA Animal Drugs for New World Screwworm page (fda.gov, updated June 2026); USDA APHIS FDA EUA announcement February 5, 2026 (aphis.usda.gov); Elanco treatment portfolio announcement June 4, 2026 (via dvm360); dvm360 FDA-authorized products list (June 19, 2026); Drovers “What Products Are Available” May 22, 2026; Zoetis US NWS product information

The FDA’s EUA framework enabled rapid treatment deployment before the first US case was even confirmed. Ivomec (ivermectin injection) received its EUA on February 5, 2026 — four months before June 3. Doramectin (Dectomax-CA1) holds the only full conditional FDA approval for NWS, providing both treatment and 21-day reinfestation protection.

The FDA EUA for generic nitenpyram OTC tablets — the “first generic animal drug authorised to treat NWS myiasis in dogs and cats” — kills most larvae within hours of the first dose, with a second dose after 6 hours. Negasunt Powder distribution is restricted to USDA-authorised users and government agencies to prevent misuse. Human treatment remains entirely manual: all larvae must be removed, sometimes surgically, as no approved anti-parasitic drug exists specifically for human NWS myiasis.

Sterile Insect Technique (SIT) and Eradication Response in 2026

USDA SIT Response — New World Screwworm Eradication (June 2026)
================================================================
Sterile flies per week (aerial)      |████████████████████████████████| 4 million
Additional ground releases/week      |████████████████████████████████| ~4 million (24 chambers x 2/wk)
Moore Air Base (Edinburg TX)         | Activated as sterile fly dispersal hub
COPEG (Panama)                       | Primary production facility; ~100M flies/week capacity
Historic eradication (1962–2006)     | 96 billion sterile flies released over 44 years
Florida Keys eradication (2016–2017) | 154 million sterile flies; 16,902 animals inspected
------------------------------------------------------------
NWS fly life cycle: ~21 days  |  SIT eradication threshold: 3 life cycles post-last-detection
Source: USDA APHIS; American Farm Bureau Federation; Drovers

Source: USDA APHIS June 3, 2026 press release; USDA APHIS June 8, 2026 press release; American Farm Bureau Federation Market Intel, June 2026; Drovers NWS History and Resurgence; dvm360 live updates June 2026

The Sterile Insect Technique is the only proven eradication strategy for NWS. SIT floods the fly population with sterilised males: female NWS flies mate only once, so a mating with a sterile male produces no viable offspring. Releasing enough sterile males breaks the reproductive cycle over successive generations. The technique was developed by USDA scientists Edward Knipling and Raymond Bushland, recipients of the World Food Prize in 1992 and described as responsible for “the greatest entomological achievement of the 20th century.”

The American Farm Bureau Federation identified sterile fly supply as the key constraint — COPEG Panama’s current production is insufficient for an expanding outbreak. The 4 million aerial flies plus ground releases per week in the Texas zone is substantial but a fraction of what wider spread would demand. USDA’s $750 million South Texas production facility is the long-term answer but is not yet operational. The response currently depends on a single Panama facility operating at capacity. USDA dyes sterile pupae fluorescent green or orange so captured sterile flies are immediately identified under UV light and excluded from surveillance case counts — essential quality control when billions of sterile flies will be released across the response zone.

Disclaimer: This research report is compiled from publicly available sources. While reasonable efforts have been made to ensure accuracy, no representation or warranty, express or implied, is given as to the completeness or reliability of the information. We accept no liability for any errors, omissions, losses, or damages of any kind arising from the use of this report.

Email ID:

Please enable JavaScript in your browser to complete this form.

Email

Email *

SUBSCRIBE