New World screwworms (NWS) are parasitic flies (Cochliomyia hominivorax) that lay eggs in open wounds, genitalia or mucous membranes such as the nostrils, eyes or mouths of live warm-blooded animals.

These eggs hatch into parasitic larvae (maggots) that only feed on living tissue, unlike other fly larvae that prefer dead or necrotic tissue. NWS larvae burrow or “screw” into living tissue with sharp mouth hooks, giving them a screw-like appearance. Infested wounds quickly become infected and, if left untreated, will kill infested animals.

Common Areas of Infestation:

·       Newborn animals’ umbilical stump/navel

·       Mucous membranes- genitalia, eyes, nose, mouth

·       Wounds- cuts, scrapes, tick bites

·       Other Areas- castration, branding

What an NWS Infestation Might Look Like:

·       Open wounds or sores with live maggots

·       Visible irritation/shaking heads

·       Foul, rotted flesh odor

“The most effective thing you can do is have eyes on your animal.”

Monitor:

·       Check for flies, maggots, larvae, or eggs.

·       Check for foul smells or drainage in and around body openings.

Isolate:

·       Animals with suspicious wounds or signs should not be moved from the current location Avoid moving animals from a pasture or premises, only pen or corral to prevent further spread Keep suspect animals in one area while you wait for collection to occur.

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If you see live animals with maggots, report immediately. Early detection is imperative. Do not delay if you suspect an NWS infestation. Reporting is crucial to managing and eradicating an NWS infestation.

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Livestock or Exotic Species

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Texas Animal Health Commission

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8 a.m. - 5 p.m., contact a local TAHC region office:

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• Amarillo (806) 641-7000

• Beeville (361) 358-3234

• Giddings (979) 212-5440

• Laredo (956) 568-5741

• Stephenville (512) 556-6277

• Sulphur Springs (903) 919-3748

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5 p.m. - 8 a.m. and on weekends, contact the TAHC headquarters: veterinarian on call (800) 550-8242

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Humans

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Contact your regional zoonosis control veterinarian.

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Texas Department of State Health Services
NWS and Humans
Zoonosis Control Contact Information

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Domestic Pets

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Contact your local veterinarian.

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U.S. Department of Agriculture (USDA)

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USDA Dashboard of Confirmed Detections

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History of New World Screwworm in the U.S.

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Texas Animal Health Commission (TAHC)

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 New World Screwworm Emergency Management Guide | PDF

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New World Screwworm Fact Sheet | PDF

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Texas Animal Health Commission New World Screwworm Livestock Producer Guidance | PDF

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