The New World screwworm, a flesh-eating parasitic fly that the United States successfully drove into South America decades ago, has reemerged in the country, prompting federal officials to take emergency action.

The parasite was recently identified in a small dog in New Mexico, marking its return to U.S. territory after being eliminated through extensive eradication efforts that began in the 1950s. Experts have been tracking the parasite's steady northward movement from South America.

In response to the detection, the Food and Drug Administration announced it has granted an emergency use authorization for medication that can treat the parasite in pets. The authorization allows veterinarians to access treatments specifically designed to combat screwworm infections in dogs and cats.

U.S. officials are now working to contain the parasite's spread using many of the same proven methods employed during the original eradication campaign decades ago. The screwworm's return tests the country's preparedness to respond to the reemergence of previously eliminated agricultural and veterinary threats.

The New World screwworm is considered a significant concern because the larvae feed on the living tissue of warm-blooded animals, potentially causing serious health problems for both livestock and pets if left untreated.