USDA Confirms Fourth New World Screwworm Case in Texas, First U.S. Infestation Since 1960s

U.S. Department of Agriculture confirmed two additional cases of New World screwworm in Texas on Monday, bringing the total number of detections to four. One case involved an infested calf in La Salle County and the other involved a dog in Andrews County.

Epidemiological investigations are ongoing for both cases. Early reports indicate the dog had recently been in Mexico, where New World screwworm flies were detected in 2024. The parasite spreads through larvae that burrow into the tissue of animals, other wildlife, and in rare cases humans.

U.S. infestation occurred in the 1960s. Dudley Hoskins, USDA under secretary for marketing and regulatory programs, said the department is simultaneously working to eradicate the pest entirely. Officials are using the sterile insect technique that involves releasing sterilized male screwworms to mate with females, which only mate once, producing infertile eggs.

The same method was used starting in the late 1950s. On Monday, Texas Gov. Greg Abbott directed state officials to escalate their response. “I have activated the full use of all state resources to respond to the New World Screwworm threat,” Abbott said in a statement.

Abbott also urged Texans to stay alert, check animals daily for wounds, and report any suspected cases immediately. The USDA secretary said the food supply is not at risk after the new cases.