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New World Screwworm (NWS) for Providers and Physicians

Clinical Presentation & Assessment

Clinical Presentation & Infestation:

Once maggots (larvae) hatch and begin to feed on live flesh, they typically cause a significant amount of pain within the infested wound. Skin wounds and sores will enlarge and deepen over time and be foul-smelling. One to several hundred maggots can often be seen within a few days of hatching and can grow up to 17mm (approx. 2/3 inch) long.

Assessment:

Healthcare providers should consider NWS if their patient:

  • Has recently traveled in areas with animal or human cases of NWS.
  • Has a very painful and foul-smelling wound with visible larvae.
  • Has a particularly deep wound with extensive tissue damage and evidence of larval infestation.
  • Has an egg mass in or around a wound or opening.

Treatment

There is currently no medication approved for the treatment of NWS infestation in humans. NWS in humans is treated by removing ALL larvae. In some cases, surgical removal may be necessary since larvae can burrow deep into wounds to feed. Healthcare providers should be aware of the potential for secondary bacterial infections associated with NWS, and patients should be clinically assessed for signs of bacterial infection.

  • Larvae and eggs should be killed by placing them into a leak-proof container with 70% ethanol. The volume of liquid in the container should be enough to fully submerge the larvae.
  • Do not dispose of extracted larvae or eggs in the trash or on the ground. 
  • Re-examine treated lesions after 24 to 48 hours to confirm no eggs or larvae remain.

Diagnosis, Specimen Preservation, & Specimen Disposal

  • Diagnosis is made through identifying morphological features of the larvae. 
  • Larvae should be removed and immediately placed into a leak-proof container with 70% ethanol. 
  • Larvae submitted for identification should be collected from different depths within the wound. 
  • Do not dispose of any larvae in the trash or outside in the ground. 
    • Submerge the remaining larvae and eggs in alcohol in a leak-proof container and place the container into a zip-top plastic bag and seal it. 
    • Dispose of the sealed bag according to your facility’s medical waste disposal protocol.
    • Failure to kill and properly dispose of all larvae or eggs may result in the new introduction and spread of NWS in the local environment. 

Notification of Public Health

Healthcare providers and laboratories should immediately report suspected NWS cases to their local health department. Report confirmed and suspected cases to the Houston Health Department at 832-393-5080, Harris County Public Health at 832-927-7575, or 713-755-5050. For all other jurisdictions within Texas, please use the corresponding reporting agency listed here. For jurisdictions reporting outside of Texas, please use the corresponding reporting agency listed here.