A fly whose larvae feed on the living flesh of warm-blooded animals. Eradicated from the U.S. in 1966; detected again in Texas in June 2026.
Affects livestock, wildlife, pets, and rarely people. Eradicated from the U.S. in 1966. For 60 years, sterile-fly releases in Panama held it south of the Darién Gap. In 2026 it moved north through Mexico and reached Texas.
Official zone boundaries: Texas Animal Health Commission zone map ↗
The chewable flea-and-tick preventives many dogs already take also kill screwworm larvae. In February 2026 the FDA authorized NexGard to treat screwworm in dogs and cats.
These are the chewables that kill the larvae:
A small number of dogs react to these. Dosing and choice are your vet's call.
Flies target any break in the skin, including a healing surgery or spay site.
Adult screwworm flies rest in shaded, brushy, wooded areas, and the deer, raccoons, and other wildlife there are their natural hosts. No cases near Austin so far.
Burrs, foxtails, and brush cause the small cuts flies use. Check and dress anything new when you come in.
Report any wild animal with a foul-smelling open wound, visible maggots, or acting sick. Do not approach. In the 1960s outbreak, screwworm killed an estimated 80% of Texas white-tailed deer.
Trim the strip where the yard meets the belt and clear carcasses or rotting debris. Flies are most active around dusk.
The same across every species: an open wound that gets worse instead of better, smells like rotting flesh, and may have visible maggots burrowing in (not crawling on top).
Texas asks for suspected cases to be reported within 24 hours.