About New World Screwworm

New World Screwworm (NWS) Information for Medical Providers

New World Screwworm (NWS) Information for Veterinary Health Providers

New World screwworm (NWS), or Cochliomyia hominivorax, is a species of parasitic fly that completes part of its lifecycle by feeding on the tissue or flesh of warm-blooded animals and people. NWS flies are attracted to wounds and body openings like the nose, eyes, ears, and mouth, where they lay eggs. The eggs hatch into maggots (larvae) that eat live tissue, causing a worsening, often painful and foul-smelling wound.

Status

There have been no reported human cases of NWS in the U.S., and the risk to the general public remains low. For the latest information on the current situation, visit the USDA website for updates.

Public Health Epidemiology Department

If you have questions about New World screwworm, contact us at: 832-927-7575 Monday – Friday: 8 AM - 5 PM; Saturday: 8 AM - 3 PM.

Symptoms

Symptoms can include:

  • Feeling maggots (larvae) move or seeing maggots within a skin wound or sore, or in the ears, nose, eyes, or mouth.
  • Painful skin wounds or sores that worsen within a few days.
  • A foul-smelling odor from the site of the infestation.
  • Bleeding from open sores.

Bacteria can also infect wounds where NWS maggots are present, potentially causing symptoms such as fever or chills.

Risk Factors

You may be at increased risk for NWS in areas where the flies are present if you:

  • Spend significant time outdoors during the day, especially if sleeping or unable to keep flies away.
  • Have open wounds, including small skin breaks from scratches, insect bites, or recent surgery.
  • Have medical conditions or treatments that cause bleeding, open sores, or skin breaks.
  • Live, work, or spend extended time around livestock, domestic, wildlife, or other warm-blooded animals.

Prevention

Preventing skin breaks and avoiding NWS flies are key to protecting yourself in areas where the flies are present. Below are additional methods to protect yourself from NWS

  • Keep open wounds clean and covered, no matter how small or where they are located on the body. 
  • Sleep indoors with closed windows or screened open windows. If you are outside, sleep under a bed net or inside a screened tent.
  • Protect your skin and prevent insect bites by:
    • Using an EPA-registered insect repellent.
    • Treating clothing and gear with products containing 0.5% permethrin per the label.
    • Wearing loose-fitting, long-sleeved shirts and pants, hats, and socks to limit access to your body by NWS flies and biting insects.

Seek Treatment

  • If you experience maggots in or on a wound or other area of your body, contact your healthcare provider immediately. Tell them if you have recently traveled to Central or South America, the Caribbean, or Mexico. 
  • Your healthcare provider will need to remove each maggot, sometimes surgically. 
  • Do not try to remove any maggots or egg masses yourself. If maggots or eggs fall out of the wound, place them in a leak-proof container with rubbing alcohol to kill them. Bring them with you to your healthcare provider.

URGENT

Do not throw any live maggots in the trash or outside as this could result in NWS spreading in your area.