Federal and state officials move quickly to contain first confirmed case in Zavala County, emphasizing livestock protection and producer vigilance.
The United States Department of Agriculture (USDA) has confirmed the detection of a New World screwworm (NWS) infestation in a calf in Zavala County, Texas, triggering a comprehensive and rapid response aimed at preventing the spread of the destructive livestock pest.
According to USDA’s Animal and Plant Health Inspection Service (APHIS), the affected animal is a three-week-old calf in which screwworm larvae were identified in the umbilical area. Officials confirm that, at this time, no additional cases have been detected.
New World screwworm is considered a serious threat to animal agriculture. The pest’s larvae burrow into the living tissue of warm-blooded animals, including livestock, wildlife, pets, and in rare cases, humans. This feeding behavior can cause severe injury, infection, and even death if left untreated, resulting in significant economic losses for producers.
Immediate Containment and Response Measures Underway
USDA, in collaboration with Texas animal health authorities, has activated a coordinated response plan to contain and eliminate the pest. The actions follow established national protocols designed to respond to NWS incursions.
Key measures include:
- Formation of a unified Incident Command Team with the Texas Animal Health Commission
- Establishment of a 20-kilometre infested zone around the detection site
- Implementation of quarantines, livestock movement controls, and enhanced surveillance
- Deployment of additional ground release systems for sterile screwworm flies
- Continuation of aerial release programs distributing approximately four million sterile flies per week
- Expanded trapping efforts along the southern border and surrounding areas
- Wildlife monitoring and targeted outreach to local producers and residents
The sterile insect technique remains a cornerstone of eradication efforts. By releasing sterilized male flies into the environment, officials aim to disrupt reproduction cycles and collapse local pest populations.
USDA Emphasizes Preparedness and Industry Collaboration
Dudley Hoskins, USDA Under Secretary for Marketing and Regulatory Programs, highlighted that the detection had been anticipated based on modeling projections.
“All models showed New World Screwworm entering the country in 2025; however, thanks to the hard work across the entire administration and our industry, state, and local partners, we were able to buy time for this moment,” Hoskins said. “Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action.”
He added that the United States has successfully eradicated the pest in the past and expressed confidence in current response efforts.
“USDA invested heavily in the tools needed to eliminate NWS ever since cases started increasing in Central America and Mexico. The United States has defeated this pest before, and we will do it again,” Hoskins said.
Producers Urged to Remain Vigilant
USDA is strongly encouraging livestock producers, veterinarians, and pet owners in the region to monitor animals closely for signs of infection.
Common indicators of NWS infestation include:
- Wounds that enlarge or fail to heal
- Drainage or discharge from affected areas
- Behavioral signs of irritation or discomfort
- Visible larvae or eggs around wounds or natural openings such as the nose, ears, or navel in newborn animals
If an infection is suspected, producers are urged to contact their state animal health officials or USDA representatives immediately to ensure rapid response and containment.
Food Supply Safety Remains Assured
Officials stress that the detection does not pose a risk to the safety of the United States food supply. Screwworms do not infest processed meat or agricultural food products.
The USDA’s Food Safety and Inspection Service (FSIS) continues to enforce strict inspection protocols under federal law. Any animals showing signs of infestation would be identified during inspection, and affected products would be excluded from the food chain.
Ongoing Efforts to Prevent Spread
The current detection follows more than a year of increased vigilance by USDA and international partners. Rising screwworm cases in Central America and Mexico prompted expanded surveillance and cross-border control measures aimed at preventing northward spread.
USDA’s National Veterinary Stockpile is also on standby, prepared to provide treatments, equipment, and logistical support as needed throughout the response.
In addition, federal officials are working with international trading partners to minimize economic disruptions. Efforts are underway to regionalize any trade restrictions, limiting impacts to defined geographic zones rather than imposing broader bans.
"The return of New World screwworm to the United States decades after its initial eradication is a disappointing milestone, but it’s also one for which dairy producers have been preparing for more than a year, in collaboration with USDA and across agriculture," said National Milk Producers Federation (NMPF) President & CEO Gregg Doud.
"It’s important to remember that this development has no effect on food safety, and that measures to combat both the screwworm and its spread are in place and time-tested. We appreciate the U.S. Department of Agriculture’s proactive efforts to prepare for this moment, and we stand ready to work with the department to address any ongoing challenges. "
Doud concluded by saying, "We also urge officials to follow scientific guidance in any decisions affecting animal movements and regulatory responses to avoid causing economic harm that could be greater than the screwworm itself. We also ask that adequate resources be provided to combat this problem, which causes suffering in animals and creates risk for producers."
responded to the announcement from the U.S. Department of Agriculture (USDA) that one case of New World Screwworm has been detected in a calf in South Texas:
"NCBA and our state partner organizations have been working for more than a year to combat the incursion of the New World Screwworm, and we are doing everything possible to protect the interests of American cattle producers," said Colin Woodall,National Cattlemen's Beef Association (NCBA) CEO.
"We defeated this harmful pest before in the 1960s by investing heavily in sterile fly dispersal and NCBA will continue using every tool in the toolbox to ensure Screwworm is eradicated in the U.S. once again."
A Critical Moment for North American Livestock Health
While only a single case has been confirmed, the detection underscores the importance of early detection and coordinated action in protecting animal agriculture.
With swift containment measures now in place and industry cooperation expected to remain strong, USDA officials remain cautiously optimistic that the outbreak can be contained before becoming more widespread.
For producers across the region, vigilance and rapid reporting will remain essential tools in ensuring the pest does not regain a foothold in the United States.
In a statement Elanco Animal health President and CEO Jeff Simmons said the company is prepared to help,"Elanco is working alongside the U.S. animal health industry to help them fight against this parasite, offering a portfolio of options for pets and livestock that can help treat New World screwworm larvae infestations."
"New World screwworm could have a devastating impact on animal health, welfare, and producer livelihoods," said Jeff Simmons, President and CEO, Elanco Animal Health. "We want to thank the FDA, EPA and USDA, for all their work to prepare for this threat. We're committed to supporting our customers during this challenging time."
Photo Credit: Pexels - Ellie Burgin