The U.S. fought the flesh-eating screwworm for decades. Now it must begin again.

EnvironmentThe U.S. fought the flesh-eating screwworm for decades. Now it must begin again.The U.S. will run much the same playbook as it did starting in the 1950s: mass-produce sterile male screwworms and release them into the wild to stop the pests from reproducing.Listen to this article with a free account00:0000:00A test container of dyed fly pupae are displayed on Feb. 9 at a facility in Edinburg, Texas, that produces sterile New World screwworms as part of the effort to stop their spread and protect American livestock.Eric Gay / AP fileShareAdd NBC News to GoogleJune 7, 2026, 6:00 AM EDTBy Evan BushThe United States spent more than half a century and hundreds of millions of dollars driving the flesh-eating New World screwworm as far from its borders as possible. Now, it’s back.Subscribe to read this story ad-free Get unlimited access to ad-free articles and exclusive content.The species can eat the tissue of any warm-blooded animal, but it’s a particular threat to livestock and is often fatal for cattle. Some environmentally minded bioethicists have openly debated whether it would be moral to deliberately drive the screwworm into extinction.“There are some species that it’s worth considering wiping out altogether and I do think the screwworm is one,” said Gregory Kaebnick, a senior research scholar at the Hastings Center for Bioethics.The Agriculture Department announced Wednesday that the New World screwworm had been found in a calf in Texas — the first detection in U.S. cattle during a natural incursion since 1982. The agency reported a second case Friday. It was discovered about six miles from the first infection. The discovery represents a worrisome comeback for the species and a failure in containment for the U.S., reprising a decadeslong battle the country waged once already.Experts said the U.S. will run much the same playbook as it did starting in the late 1950s, when the government embarked on an aggressive, multinational fight against the screwworm....