New World Screwworm Detected in Texas Calf

The New World screwworm has been confirmed in a calf in Zavala County, Texas, marking the first detection of this parasite in U.S. livestock in decades. The Department of Agriculture announced on June 4, 2026, that a three-week-old calf tested positive for the parasite, which feeds on the living tissues of warm-blooded animals. This confirmation follows a suspected case reported the previous day and comes amid a growing outbreak in Mexico. According to the USDA, the infestation was found in the calf's umbilical area, and no additional cases have been identified in the U.S. The USDA reassured that the food supply remains safe as screwworms do not infest food products. The USDA has urged residents to contact veterinarians if they observe any suspicious signs in their animals. The current outbreak in Mexico has led to increased surveillance and actions to prevent the spread of the screwworm into the U.S.