Screwworm Coalition
of Texas

Report Suspicions

Identification

New World Screwworms Can Infest a Variety of Wounds:

  • Branding site
  • Castration site
  • Dehorning wound
  • Ear notch or tagging site
  • Scratch or cut
  • Tick bite
  • Umbilical cord
  • Eye, naval or genital area
  • Any open wound or other exposed areas of soft tissue

Signs of New World Screwworm in Animals

A close-up image of a fly with red eyes and transparent wings feeding on a dark, decomposing organic material.
Fly with egg mass on wound
A close-up image of a wound infested with maggots and flies on animal skin.
Close-up female fly, eggs, and larvae on wound
Dog with a severe open wound on its neck infested with maggots, displaying extensive tissue damage and hair loss.
Severe NWS Myiasis on dog’s neck
Deer head with severe injury and exposed tissue, covered in maggots, lying on a rough, gray surface.
Infested deer with extensive tissue damage
Close-up of an open wound on an animal with multiple green flies on the exposed tissue.
NWS flies attracted to an animal wound

NWS larvae and their feeding cause extensive damage by tearing at the hosts’ tissue with sharp mouth hooks. The wound will become larger and deeper as more and more eggs hatch and larvae feed on the living tissue. This results in severe and sometimes fatal damage to the animal if not discovered and treated.

What to Look For

Producers, wildlife managers, and landowners should be alert for possible signs associated with potential infestation including:

1. Irritated behavior
2. Head shaking
3. The smell of decayed flesh
4. The presence of larvae in a wound
5. Biting or licking at wounds

Egg masses may be around or in the wound. Larvae may be visible by the third day of infestation.

Because they feed on live flesh, NWS larvae may burrow deep into wounds or openings, while other species of larvae may appear around the outer surface of the wound.

Screwworm infestations are very painful. Animals may become depressed, stop eating, and separate themselves from other animals or people.

Monitor for signs

Monitor pets and livestock for clinical signs of NWS, myiasis, or secondary infections. If you notice the presence of fly larvae in wounds, evidence of fly strike, and smell of decaying flesh, immediately report suspicions.

Call a Veterinarian

Veterinarians can help identify NWS if you see signs of a potential infestation in livestock, pets, or wildlife on your property. Veterinarians can report cases, submit samples of larvae to labs, and guide you on how to reduce risk on your operation.

Report Suspicions

All suspicions of NWS infestation must be reported with 24 hours to the appropriate agency. For more information on reporting, go HERE.

Additional Resources

For downloadable pdfs and resources on NWS, visit the Resources page.

If you suspect an NWS infestation, you should immediately report it here.