New World Screwworm Tracker
A flesh-eating parasite spreading north toward the United States. Track USDA-confirmed detections by county and follow the outbreak's advance through Central America and Mexico.
Current detections & spread
Red markers are USDA-confirmed US detections (sized by number of animals). Dashed amber markers trace the outbreak's reported northward spread.
About the parasite
What it is
A parasitic infestation (myiasis) caused by the larvae of the New World screwworm fly, which lay eggs in the open wounds or mucous membranes of live, warm-blooded animals. Unlike most maggots, screwworm larvae feed on living tissue, producing rapidly enlarging, potentially fatal wounds. Eradicated from the United States in 1966, it is re-emerging via northward spread from Central America and Mexico and is a federally reportable foreign animal disease.
Signs in animals
A wound that enlarges and deepens over days rather than healing, often with a foul odor and serous or bloody discharge; visible maggots burrowing head-down into living tissue; irritation, restlessness, head-shaking, loss of appetite, isolation from the herd. Untreated infestations can kill an animal within one to two weeks.
How animals get infested
Female flies lay egg masses at the edges of even minor wounds — tick bites, scratches, castration, branding or dehorning sites, and especially the navel of newborns — or on mucous membranes (nostrils, eyes, genitalia). Hatched larvae burrow into living flesh. Geographic spread is driven by adult fly flight and by moving infested animals.
Prevention
Inspect animals daily for wounds during fly season and treat and cover wounds promptly; minimize elective wounding procedures when flies are active; monitor newborn navels. Report any suspected case immediately to your state veterinarian or USDA APHIS (1-800-940-6524) — it is a reportable disease. Area-wide control relies on the sterile insect technique (release of sterile male flies).
🚨 Report a suspected case
New World Screwworm is a reportable disease. If you see a wound with maggots that is enlarging rather than healing, act immediately — don't wait.
- USDA APHIS: 1-800-940-6524
- Contact your state veterinarian or local USDA office.
- Isolate the animal and preserve any larvae for identification.
USDA-confirmed US detections (13 counties)
| County | State | Animals | Reported |
|---|---|---|---|
| Crockett | Texas | 8 | Jun 25, 2026 |
| Edwards | Texas | 6 | Jun 22, 2026 |
| Terrell | Texas | 4 | Jun 24, 2026 |
| Zavala | Texas | 3 | Jun 3, 2026 |
| La Salle | Texas | 2 | Jun 14, 2026 |
| Jim Hogg | Texas | 1 | Jun 29, 2026 |
| Tom Green | Texas | 1 | Jun 28, 2026 |
| Pecos | Texas | 1 | Jun 27, 2026 |
| Sutton | Texas | 1 | Jun 26, 2026 |
| Medina | Texas | 1 | Jun 20, 2026 |
| Uvalde | Texas | 1 | Jun 18, 2026 |
| Gillespie | Texas | 1 | Jun 15, 2026 |
| Lea | New Mexico | 1 | Jun 15, 2026 |
| Total | 31 | ||
Source: USDA APHIS "Confirmed Detections of New World Screwworm." Counts are aggregated by county and updated automatically. Regional Central America / Mexico figures are cumulative reported cases (USDA APHIS / COPEG / SENASICA) shown for context.