U.S. confirms first human case of flesh-eating screwworm parasite

The United States has confirmed its first human case of the New World screwworm, a gruesome flesh-eating parasite, according to the Department of Health and Human Services (HHS).

The case involved a Maryland resident who had recently traveled to El Salvador. While officials stress that the immediate risk to the American public is very low, the incident casts a spotlight on a burgeoning outbreak among livestock in Central America that U.S. authorities view as a significant threat to the nation’s food supply.

The patient has since made a full recovery, and the Maryland health department confirmed there was no evidence of further transmission.

An HHS spokesperson stated that the screwworm, known scientifically as Cochliomyia hominivorax, is a parasitic fly whose larvae, or maggots, infest the open wounds of warm-blooded animals, including humans.

The maggots feed on living tissue, using sharp mouth hooks to screw themselves deeper into the flesh, causing severe damage that is often fatal for the host animal.

This human case emerges as Central American nations grapple with a massive outbreak of the parasite in livestock.

The U.S. Department of Agriculture (USDA) noted a dramatic surge in Panama, where cases skyrocketed from an annual average of 25 to over 6,500 in 2023.

The parasite has since been detected in seven other Central American countries, breaching a containment barrier that had kept it confined to South America for decades.

The U.S. has been free of screwworm for many years, thanks to a successful eradication program that released sterilized male flies to disrupt the reproductive cycle and cause the population to die out.

However, the escalating situation in neighboring countries has prompted significant concern. The USDA has warned that the parasite is “a threat to our ranching community… our food supply and our national security.”

In response, the agency is bolstering defenses, including building a new sterile fly production facility in Texas, deploying mounted patrols and detector dogs to monitor border crossings, and temporarily banning certain livestock imports from Mexico.

The Food and Drug Administration (FDA) has also issued an Emergency Use Authorization for animal drugs to treat and prevent screwworm infestations.

The Centers for Disease Control and Prevention (CDC) advises that individuals traveling to affected regions, particularly those with open wounds who spend time outdoors or near livestock, are at a greater risk of infection.