New World Screwworm

Aka: New World Screwworm, NWS Myiasis, Cochliomyia Hominivorax, Cochliomyia Hominivorax Larva

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II. Epidemiology

  1. New World Screwworm was eradicated from the U.S. in the 1960s
  2. U.S. cases have typically been rare and associated with traveler to endemic regions
    1. Central and south america
    2. Cuba
    3. Haiti
    4. Dominican Republic
  3. As of 2025, increase in U.S. cases
    1. Major concern for significant chronic morbidity

III. Pathophysiology

  1. New World Screwworm (NWS, Cochliomyia Hominivorax)
    1. Type of blowfly
    2. Adult fly appearance
      1. Bright orange eyes
      2. Metallic blue-green body
      3. Back with 3 dark stripes
    3. Hosts
      1. Blowfly, are found primarily around livestock and mammalian wildlife
  2. New World Screwworm infestation
    1. NWS Blowfly is attracted to open wounds in live tissue
    2. NWS Blowfly lays eggs in open wounds of its mammalian hosts (e.g. livestock, wildlife, pets, humans)
    3. Eggs hatch into larvae (Maggots)
    4. Larvae (Maggots) that are invasive and destructive of infected tissue

IV. Signs

  1. Progressive, non-healing necrotizing wound with extensive tissue destruction
  2. Associated findings
    1. Skin Ulcers
    2. Foul-smelling necrotic tissue

V. Complications

  1. Secondary Bacterial Infections (common)

VI. Labs: Diagnosis

  1. Wound biopsy
    1. Demonstrates New World Screwworm larvae

VII. Management

  1. Urgent, complete surgical Debridement of larvae infested wound
    1. Typically combined with Antibiotic coverage of superinfection
  2. Antibiotics
    1. Treat secondary Bacterial Infection (broad spectrum Antibiotics cover aerobes and Anaerobes)
  3. Wound Care
    1. Prevent further infestation
    2. Promote full Wound Healing

VIII. Prevention

  1. Monitoring of livestock and wildlife to prevent local reservoirs of New World Screwworm
  2. Traveler education regarding risks to endemic regions (rural south and central america, livestock exposure)
  3. Prompt evaluation and management of exposed patients with suspicious wounds
  4. Consult CDC Parasitic Disease expert as needed

IX. Resources

  1. New World Screwworm (CDC)
    1. https://www.cdc.gov/new-world-screwworm/hcp/clinical-overview/index.html

X. References

  1. (2025) New World Screwworm - Emerging U.S. Threat, 10/20/2025

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