USDA Confirms New World Screwworm Case in Northern Mexico, 62 Miles from Texas Border

U.S. Department of Agriculture confirmed a New World screwworm case in the Mexican state of Nuevo León, approximately 62 miles from the Texas border. This marks the northernmost active case in Mexico. Federal health officials reported on Monday, April 21, 2026, that cases of the flesh-eating parasitic infection continue to be detected near the United States.

U.S. remains very low. U.S. New World screwworm is a species of parasitic fly that feeds on live tissue and can cause myiasis, an infestation of larvae or maggots. It can infest many types of animals, including livestock, pets, wildlife, and in rare instances, humans.

"These maggots actually feed on the tissue in the wound and can destroy that tissue very substantially," said Dr. William Schaffner, professor of preventive medicine at Vanderbilt University Medical Center in Nashville. " A female New World screwworm will find a living host and land in an open wound, even as small as a tick bite, around the eyes, ears, nose, and mouth.

She will lay between 200 and 300 eggs. After the eggs hatch, the maggots burrow further into the tissue and cause painful infestations. "It can cause deadly wounds in animals," said Dr. Todd Ellerin, chief of infectious diseases at South Shore Health in Massachusetts.

" Ellerin noted that rarely, it can lay an egg in human wounds that can then become secondarily infected with bacterial infections and cause severe infections. After feeding for about seven days, larvae drop to the ground, burrow into the soil, and emerge as adult screwworm flies.

U.S. And is present in countries in Central and South America as well as the Caribbean. , but the southern states that border there are at higher risk than the northern states," Ellerin said. NWS infection can cause skin lesions that don't heal or worsen over time, painful wounds or sores, bleeding from open sores, feeling or seeing maggots in wounds, or a bad odor from the site of the infestation.