USDA confirms New World screwworm case in Texas calf, launches emergency response

USA – The U.S. Department of Agriculture (USDA) has confirmed the detection of New World screwworm (NWS) in a three-week-old calf in Zavala County, Texas, prompting immediate containment and eradication measures to prevent the pest from becoming established in the United States’ livestock sector.

According to the USDA’s Animal and Plant Health Inspection Service (APHIS), larvae were found in the calf’s umbilical area. Officials reported that no additional cases have been detected so far.

New World screwworm, caused by the parasitic fly Cochliomyia hominivorax, is considered one of the most destructive livestock pests due to its ability to infest living tissue.

The larvae burrow into open wounds and feed on the flesh of warm-blooded animals, causing severe injuries, production losses and, in some cases, death.

“All models showed New World screwworm entering the country in 2025; however, thanks to the hard work across the entire Trump administration and our industry, state, and local partners, we were able to buy time for this moment,” said Dudley Hoskins, USDA Under Secretary for Marketing and Regulatory Programs.

“Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action.”

The detection marks a significant concern for the cattle industry, given the pest’s historical impact on livestock production. 

Before its eradication from the United States in the 1960s, New World screwworm caused substantial economic losses across the livestock sector.

Sterile fly releases and quarantine measures activated

USDA and Texas animal health authorities have activated the response measures outlined in the agency’s New World Screwworm Response Playbook.

Actions include establishing a unified incident command structure involving USDA and the Texas Animal Health Commission, deploying response personnel, and creating a 20-kilometre-wide infested zone around the detection site.

Movement controls, quarantines and enhanced surveillance have also been implemented within the affected area.

To suppress the pest population, the USDA is accelerating the release of sterile male screwworm flies, a proven eradication technique that was instrumental in eliminating the pest from the United States decades ago.

The agency said ground-release chambers will be deployed immediately, in addition to the four million sterile flies already being released each week aerially in the region.

Authorities are also increasing trapping activities along the U.S.-Mexico border, strengthening surveillance in wildlife populations and conducting outreach to producers and residents in the affected area.

“USDA invested heavily in the tools needed to eliminate NWS ever since cases started increasing in Central America and Mexico,” Hoskins said. 

“The United States has defeated this pest before, and we will do it again.”

The agency’s National Veterinary Stockpile has been placed on standby to provide treatment products, equipment and logistical support as required.

USDA emphasised that the U.S. food supply remains safe, noting that screwworms do not infest meat, poultry, eggs, fruits or vegetables. 

The agency said federal meat inspection procedures would identify any evidence of infestation in slaughter animals, preventing affected products from entering commerce.

Over the past year, USDA has intensified surveillance and cross-border control efforts in Mexico and Central America as New World screwworm cases moved northward. 

The agency said those measures helped delay the pest’s arrival while allowing time to strengthen domestic preparedness and response capabilities.

USDA is urging livestock producers and pet owners in the affected area to closely monitor animals for draining wounds, signs of discomfort or the presence of screwworm larvae and eggs around wounds and body openings, particularly in newborn animals.

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