A flesh-eating fly that was once eradicated from the United States is moving north again, raising concerns for livestock, wildlife, pets, and in rare cases people.
The New World screwworm is the larval stage of a blowfly. Its name comes from how the larvae bore into tissue like a screw into wood. Unlike most maggots, which feed on dead tissue, screwworm larvae consume living flesh, often entering through wounds and causing severe infections.
The pest once caused widespread losses for American livestock producers. In the 1950s, damage in the Southwest alone was estimated at $50 million to $100 million a year. A massive eradication campaign using millions of sterile male flies eventually eliminated the pest from the U.S. and pushed its range south to Panama.
But the pest has returned and has reached as far north as Texas and New Mexico.
Researchers at the University of California San Diego have developed a new tracking tool to help officials anticipate where the pest could spread to next. The system combines confirmed detections with environmental conditions that favor the fly and reports from news organizations, which can sometimes provide warnings before official confirmation.
The U.S. Department of Agriculture is leading the new eradication campaign. It’s once again releasing sterile flies, as well as using pesticides and quarantines to try to limit the spread.
The return of the New World screwworm demonstrates how difficult it can be to permanently eliminate biological threats.
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The U.S. Eradicated this flesh-eating parasite. Now it’s back
