First U.S. Case of New World Screwworm Myiasis Confirmed; Authorities Launch Massive Containment Plan

August 26, 2025
First U.S. Case of New World Screwworm Myiasis Confirmed; Authorities Launch Massive Containment Plan
  • Texas faces substantial economic risk from screwworms, with USDA estimating potential losses of at least $1.8 billion in livestock deaths, labor costs, and medications.

  • Recent regional developments include a November 2024 screwworm outbreak in Mexico that led to a temporary pause on U.S. livestock imports at the southern border, followed by phased reopenings and the establishment of a new sterile fly dispersal facility in southern Texas.

  • Historically eradicated in parts of the U.S., New World screwworms have reemerged since 2023, with increasing northward spread from Central America and the Caribbean.

  • In humans, myiasis presents as non-healing wounds with visible larvae; treatment centers on manual removal of larvae since there are no approved drugs for NWS in humans or animals.

  • The case underscores the importance of robust surveillance, proactive public health funding, and awareness of travel-related risks in safeguarding public health.

  • The United States has confirmed its first human case of New World screwworm myiasis, involving a Maryland resident who had recently traveled to El Salvador and has since recovered.

  • The case was confirmed by the CDC, with travel-related exposure linked to the trip to El Salvador.

  • Public health officials say the immediate risk to U.S. public health remains very low, based on current surveillance.

  • Authorities are emphasizing containment measures aimed at keeping the parasite south of the U.S. border to protect livestock and public health.

  • The sterile-fly program relies on releasing sterile males to mate with females, producing non-viable eggs and reducing populations, a method that helped eradicate outbreaks in the 1960s.

  • USDA announced a five-part, large-scale plan to combat the screwworm, including billions of sterile flies released over southern Texas and Mexico, a new Texas sterile fly facility, and enhanced border inspections.

Summary based on 5 sources


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