Screwworm returns to Texas livestock and wildlife six decades after U.S. eradication

Summary

The screwworm, a flesh-eating parasite, devastated livestock from Florida to Texas for much of the 20th century and was eliminated in the U.S. in 1966.
On June 3, 2026, screwworm larvae were found in a three-week-old calf in Zavala County, Texas, marking the parasite's return.
Within days, screwworm was confirmed in three other Texas counties and in a dog in New Mexico that had crossed state lines.
On October 21, 2026, the Department of Agriculture confirmed the first wildlife detection, an elk on a game ranch in Pecos County, Texas.
More than 60 confirmed cases in domestic animals have followed, plus a case in another Texas elk.
The historic outbreak cost more than $1 billion annually in today's dollars and killed thousands of animals each year.

Author Alison L. Davis argues the technique that eliminated screwworm from the U.S. once will not be enough to eradicate it again.
Scientific American forecasts more screwworm infections could emerge during the late 2026 hunting season, particularly in wildlife, as hunters encounter affected animals.

We beat screwworm once. Here’s how we’re trying to do it againscientificamerican.com· 9h
Scientific American recounts how the flesh-eating screwworm parasite, eliminated from the U.S. in 1966 after devastating livestock from Florida to Texas, reemerged in 2026 with detections in Texas cattle, wildlife, and New Mexico, and forecasts more infections during the hunting season. Author Alison L. Davis argues the eradication technique that worked once won't be enough again.