New World screwworm has breached U.S. borders for the first time in six decades, triggering an emergency response that now stretches from South Texas ranches to the halls of Washington.
Background on New World Screwworm
Furthermore, this pest carries a brutal history in American agriculture. After 60 years of successful eradication, New World screwworm has been detected in Texas. Since 2023, an outbreak of NWS has moved northward through Central America and Mexico, primarily infesting livestock, pets, and wildlife, but also people. However, federal agencies held the line for years. For more than a year, USDA led a unified response to NWS, deploying advanced surveillance systems and supporting robust cross-border response efforts in Mexico and Central America. NWS larvae burrow into the flesh of living animals, causing serious damage to livestock and economic losses. Notably, untreated animals face deadly consequences. NWS myiasis is often fatal in untreated cattle within 14 days.
Key Details of the New World Screwworm Outbreak
On June 3, 2026, USDA’s Animal and Plant Health Inspection Service confirmed the detection of a New World screwworm in a bovine in Zavala County, Texas. The first confirmed U.S. case involved a three-week-old beef calf in La Pryor, Texas, in southwestern Zavala County, approximately 50 miles from the Mexico border — a rancher observed signs of distress and contacted a veterinarian after discovering larvae in the calf’s umbilical area. Moreover, the pest spread quickly after that initial find. Since then, additional detections have been confirmed in Zavala, La Salle and Gillespie Counties in Texas, as well as Lea County, New Mexico. The newly identified cases involve a calf in La Salle County, Texas; a goat in Gillespie County, Texas; and a dog in Lea County, New Mexico, bringing the total number of confirmed cases to five. In addition, the CDC escalated its involvement. CDC is supporting USDA and the Texas Department of State Health Services in responding to the initial detections of New World Screwworm infestations in animals in southern Texas and in one county of New Mexico.
Industry Impact of New World Screwworm
The flesh-eating fly poses a threat to the state’s $15 billion cattle industry. Consequently, trade partners reacted swiftly. Canada temporarily restricted livestock imports originating from Texas following the confirmed detections. Furthermore, market analysts noted a complicated cattle futures reaction. Cattle futures rallied to fresh near-term highs, with U.S. screwworm cases reinforcing tight supplies. While the detection of NWS is a fundamentally bullish event, it comes at a challenging time for the U.S. cattle industry — added costs and risks associated with NWS and the threat of another severe drought year only amplify the challenges that have led to reductions in the cattle inventory. Meanwhile, economic projections alarmed producers. An outbreak of screwworm threatens to do $1.8 billion in damage to Texas’ economy alone, according to a USDA estimate. According to USDA estimates, there were just over four million head of beef cattle in the state of Texas at the beginning of 2026.
What Comes Next for New World Screwworm Response
Therefore, USDA deployed its most aggressive tools. The strategy to respond to and control the NWS outbreak, led by USDA and in coordination with other federal agencies, includes the release of sterile flies, animal movement controls and surveillance, and outreach and education in affected areas. USDA has also established a dedicated New World Screwworm Directorate within APHIS to coordinate the federal response. Importantly, officials appointed a new point person at the top. U.S. Secretary of Agriculture Brooke L. Rollins announced President Donald J. Trump has appointed John Bellinger as the new Senior Advisor for New World Screwworm Preparedness. Moreover, the FDA rushed treatments to producers. The FDA issued an Emergency Use Authorization for generic Nitenpyram Tablets, making it the first generic animal drug authorized to treat New World screwworm myiasis in dogs, cats, puppies, and kittens. To prevent further spread of NWS, TAHC issued an executive director order that places a quarantine on all warm-blooded animals in the identified infested zone in the Zavala County area. The greatest need among stakeholders remains a significant expansion in sterile fly production to effectively combat NWS and achieve the long-term goal of re-eradication.
Conclusion
As a result, every rancher in Texas and beyond now faces a new operational reality. Early detection, prompt reporting and treatment — backed by coordinated surveillance along the border — will be critical to keeping this treatable pest contained, with ranches tightening calving seasons, upgrading working facilities and revisiting parasite control plans with their veterinarians. USDA officials continue to express confidence that aggressive and proactive containment measures will prevent the severe economic scenarios of a New World Screwworm outbreak that have been modeled in earlier studies. Ultimately, the return of New World screwworm reminds America’s livestock sector that the battle against invasive pests never truly ends — only the scale of readiness changes.
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Originally reported by USDA Animal and Plant Health Inspection Service (APHIS). Analysis by the GardenScoop Editorial Team.
