EDWARDS COUNTY, Texas – In a concerning development for livestock health, the U.S. Department of Agriculture (USDA) reported three new cases of New World Screwworm within a 24-hour period. This brings the total number of confirmed cases in the United States to 15, highlighting the ongoing threat posed by this parasitic fly.
Among the new detections, two cases were found in calves located in Edwards County, an area already experiencing an outbreak. The USDA noted that these animals were within the currently affected zone, emphasizing that the situation remains dynamic despite ongoing control measures.
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🚨NWS UPDATE: In the last 24 hours, 1 lamb in Crockett County, TX and 2 calves in Edwards County, TX have tested positive for New World Screwworm, bringing the total number of domestic confirmed detections to 15. @USDA has already taken action and will be starting sterile fly…
— New World Screwworm Rapid Response (@Screwworm_RR) June 21, 2026
The USDA explained that the emergence of new cases was anticipated, even with the implementation of sterile fly dispersals in the region. These measures are designed to prevent future generations of the screwworm but do not eliminate existing larvae. The agency highlighted the importance of understanding the fly’s life cycle, which averages 21 days, indicating that multiple reproductive cycles must occur for the populations to diminish effectively.
“Because a fly’s life cycle is an average of 21 days, it takes multiple reproductive cycles for populations to die off following sterile fly releases,” the USDA stated. “As such, we may continue to see cases occur in already affected zones — a sign that our surveillance is working.”
In addition to the Edwards County cases, another instance of New World Screwworm was identified in a lamb in Crockett County, Texas, which is adjacent to the previously affected areas. In response, the USDA plans to initiate sterile fly dispersal flights over Crockett County to combat the new infestation, illustrating the proactive measures being taken to protect livestock health.
For those interested in tracking the spread of this pest, the Texas Animal Health Commission provides a comprehensive map of infested and adjacent surveillance zones on its official website. This resource is invaluable for ranchers and livestock owners as they navigate the challenges posed by New World Screwworm.
