New World screwworm reappears in the United States, prompting tracking and eradication efforts

The larval stage of the blowfly Cochliomyia hominivorax, known as the New World screwworm, has been confirmed in Texas and New Mexico, marking its return to the United States after eradication in the 1950s. The parasite can infest open wounds and body openings of warm-blooded animals, including livestock, wildlife, pets and, rarely, humans, where it feeds on living tissue and can cause secondary infections.

Researchers at the University of California, San Diego and the San Diego County Health and Human Services Agency have created an online dashboard that generates county-level risk profiles by combining confirmed sightings, environmental data and media reports. "Traditional reporting mechanisms for public health are often delayed," said Seema Shah, medical director of the county’s Epidemiology and Immunization Services Branch. "By incorporating media reports, we can identify potential threats sooner and stay one step ahead."

Assistant medical director Mark Beatty added that the tool helps officials gauge whether a threat is imminent or months away, aiding preparation and response planning. The dashboard is currently limited to public-health officials, with a public version under consideration.

The screwworm spreads when adult flies travel in search of hosts and when infested animals move into new regions. The USDA is reviving the sterile-insect technique that eliminated the pest in the 1950s, pairing sterile male releases with pesticides and animal-movement quarantines. Officials are also seeking EPA approval for a genetically modified all-male strain and are exploring next-generation genetic technologies.

Veterinarian Emily Trumbull, lead of the county’s One Health program, emphasized collaboration with local veterinarians to monitor and report suspected cases across livestock, pets and wildlife, noting the importance of early detection to prevent human infections.