New World screwworm is a fly whose larvae feed on the living flesh of warm-blooded animals, entering through wounds, navels or brands. It has spread north through Mexico. Texas tracks infested and surveillance zones; this week the nearest infested zone is shown below.
Nearest active screwworm zone
| Straight-line from Amarillo | about 279 miles |
| Zone | Infested Zone 27 |
Rough distance to the nearest edge of an active zone on TAHC's map.
Source: Texas Animal Health Commission · as of Oct 31, 2026
Female flies lay eggs in open wounds, fresh navels on newborn calves, tick bites or cuts from dehorning, branding and castration. The larvae (maggots) burrow into live tissue, and an untreated case can kill an animal in days. People and pets can be infested too.
The U.S. eradicated screwworm decades ago by releasing sterile flies, and that is again the main control tool as the pest has moved north through Mexico.
In Texas, the Texas Animal Health Commission (TAHC) sets infested and surveillance zones by order and publishes a zone map. Cownty reads TAHC's map and orders and shows each Texas region county's status and its distance to the nearest infested zone.
What to watch for: wounds that won't heal, a foul smell, animals off by themselves, or larvae in a wound. Check navels and fresh cuts closely in warm weather.
If you suspect a case, call TAHC or your veterinarian right away. Don't wait for a lab or ship the animal. Collect larvae only if your vet tells you how.
Official sources
Rules checked against these pages on Oct 18, 2026. Live numbers update with each data load. Information only: the agency decides. Not affiliated with USDA.