Human Case of New World Screwworm Confirmed in the U.S.

Dan Cattle, Pest/Pest Control

First Human Case of New World Screwworm Reported in the U.S.
human case
New World screwworm (NWS, Cochliomyia hominivorax) is a devastating pest. When NWS fly larvae (maggots) burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal. NWS can infest livestock, pets, wildlife, occasionally birds, and in rare cases, people.
Courtesy of USDA/APHIS

The Department of Health and Human Services has confirmed the first human case of New World Screwworm (NWS) in the United States, according to a recent report. The diagnosis was confirmed by the Centers for Disease Control and Prevention (CDC).

The rare parasitic infestation appeared in a traveler returning from Central America, where the disease is already endemic. “The disease appeared in a traveler who’d been returning to the U.S. from Central America, where the disease is already present.”

State veterinarians were alerted during a CDC call last week. Oklahoma State Veterinarian Dr. Rod Hall provided more insight: “The patient lives in Maryland, where officials said they’re confident it is contained. Dr. Hall added that he believes the U.S. is probably more likely to get it in a person or pet than in livestock, at least in the short term.”

The New World Screwworm is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals, including humans. While the U.S. eradicated NWS in domestic livestock decades ago, sporadic cases in people or animals traveling from affected regions can still occur.

South Dakota State Veterinarian Beth Thompson shared additional information with Reuters: “When NWS was confirmed in Maryland, the CDC worked with local physicians to identify the larvae.”

Officials emphasized that there are no livestock movement restrictions in place at this time. The case appears isolated, and rapid coordination between state and federal agencies has helped prevent further spread.

While this is a significant public health event, experts agree the risk to livestock remains low for now. However, veterinarians and health professionals are advised to stay vigilant, particularly for animals or travelers returning from Central America or other endemic regions.

This incident underscores the importance of early detection and international cooperation in preventing the reintroduction of dangerous parasites to U.S. soil.

Human Case of New World Screwworm Confirmed in the US