New World Screwworm Confirmed in United States, USDA Announces

The USDA has confirmed the first U.S. case of New World screwworm (NWS) in decades, identifying larvae in a 3-week-old calf in Zavala County, Texas. NWS is a serious, reportable foreign animal disease whose larvae feed on living tissue, threatening livestock, pets, wildlife, and occasionally humans. Veterinarians and producers are being urged to inspect animals for suspicious wounds, larvae, or eggs and report suspected cases immediately.

Federal and Texas officials have activated an emergency response, including quarantines, movement controls, expanded surveillance, and increased releases of sterile flies to suppress the pest. The detection follows nearly a year of preparation, during which the FDA issued emergency authorizations for multiple NWS treatments across species.

Historically eradicated from the U.S. through sterile insect releases, NWS has steadily advanced northward from Central America since 2022. Officials emphasize that the U.S. food supply remains safe and that rapid detection and response are critical to preventing the parasite from becoming reestablished.