The United States Department of Agriculture confirmed this week the first known infection of screwworm fly larvae in the country since the parasitic insects were successfully eradicated in the 1960s.

Screwworms are carnivorous fly larvae that feed on the flesh of living mammals. The parasites burrow into wounds and healthy tissue, creating serious health risks for both livestock and humans. The flies were once a major agricultural and public health threat across the southern United States.

The USDA achieved the elimination of screwworms from the United States through an innovative sterile insect technique program launched in the 1950s. The program involved releasing millions of sterile male flies to disrupt the reproductive cycle of wild populations.

The confirmation of a new infection raises concerns about potential reintroduction of the species, though officials have not yet disclosed details about the location or circumstances of the detected case. The USDA has maintained surveillance programs to monitor for any return of the parasites.

Screwworm infestations can cause significant economic losses to livestock operations and pose health risks to wildlife and domestic animals. The agency previously estimated that the eradication program has saved billions of dollars in agricultural losses since its implementation.