#19,192
Three days ago we saw the USDA Confirm the Presence of New World Screwworm (NWS) in the United States (Texas) for the first time since the 1960s. The NWS is a parasitic fly that lays its eggs in the open wounds of warm-blooded animals (often cattle and deer, but occasionally humans and pets).
Unlike most fly maggots, NWS larva consume and burrow into living tissue, causing substantial morbidity and mortality. (See ASM 2025 Review New World Screwworm: Rise, Fall and Resurgence).
Not unexpectedly, this weekend we are learning of a 2nd case, found in a calf a little more than 5 miles away from the first case.
Although the risk to public health is extremely low, this agricultural pest can be devastating for the cattle industry.
The Texas Governor's office has officially declared two counties ( Zavala & Uvalde) as disaster areas, and has committed the full resources of the state to combat the threat.
Governor Abbott Deploys State Resources To Combat New World Screwworm
June 5, 2026 | Austin, Texas | Press Release
Issues Disaster Declaration for Zavala and Uvalde Counties
Governor Greg Abbott today received a briefing and updated Texans on the state’s response following confirmation of a New World Screwworm (NWS) detection in Texas. The Governor also issued a disaster declaration for Zavala and Uvalde Counties.
“I am issuing an updated statewide disaster declaration to make two things very clear,” said Governor Abbott. “First, I authorize the use of all available resources of state government to respond to this disaster and reassign resources from across the state as needed to address NWS. Second, I am making all state personnel available to accelerate the movement of sterile flies into Texas and the construction of the new sterile screwworm production facility in Edinburg. We have eradicated this pest before, and we will do it again.”
Excerpts from the USDA's announcement follow:
Animal Health Officials Respond to Second Detection of New World Screwworm in the United States
FOR IMMEDIATE RELEASE
Contact: screwworm@usda.gov
WASHINGTON, D.C., June 5, 2026 — The U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) has confirmed a second detection of New World screwworm (NWS) after testing a number of suspect cases. The confirmed case was found in a one-month-old calf in Zavala County, Texas, approximately 5.6 miles away from the first confirmed detection. APHIS and our Texas partners continue to collect and test other samples from the surrounding area which have come back negative.
NWS is a serious pest that threatens livestock, pets, wildlife, and, in rare cases, people. The larvae burrow into the living tissue of animals, causing severe wounds, animal suffering, and significant economic losses.
“USDA has responded expediently with respect to this second detection, demonstrating our utmost preparedness. This second detection is within the established movement control zone and enhanced sterile insect dispersal area.” said Dudley Hoskins, Under Secretary for Marketing and Regulatory Programs. “Many models projected this pest would reach the United States last year, but thanks to USDA’s phenomenal work and our cooperation with state, federal, and industry partners, we’ve held it off until now—when we are far more prepared to respond. USDA has not wasted any time in this fight, we have defeated New World screwworm before, and we will do it again."
USDA Strike Team and Rapid Deployment Capacity
An APHIS strike team is already on-site in Texas. This team includes veterinary medical officers and animal health technicians – experienced experts who serve as USDA’s boots on the ground response force. APHIS is fully positioned to surge additional trained personnel as needed.
The National Veterinary Services Laboratories (NVSL) has deployed an entomologist to the USDA Agricultural Research Service laboratory in Kerrville, Texas, to expedite confirmation processes by positioning NVSL diagnostic assets in the area.
APHIS has also deployed two dedicated NWS response cargo trailers. Each 24-foot trailer serves as a mobile preparedness and field operations center. Once unloaded, the trailers convert into operational and laboratory space, providing USDA personnel with the equipment and environment necessary to mount a rapid, efficient response.
Treatment Resources and Supplies
The U.S. Food and Drug Administration has issued emergency use authorizations for several NWS treatments for different species. Currently, there are treatments available to support cattle, horses, swine, goats, captive exotic animals, and wildlife.
The National Veterinary Stockpile is actively procuring additional tools to treat and prevent NWS. USDA is working with federal and regulatory partners, and within federal purchasing processes, to secure more treatment options that are flexible, safe, and effective.
The National Veterinary Stockpile has relocated NWS treatment supplies to Texas to better support affected producers in the infested zone. If you or anyone you know needs access to these treatment supplies, they are now available and can be obtained by reaching out directly to the Texas Animal Health Commission (TAHC).
Intensified Sterile Fly Operations
As part of the established NWS eradication strategy, USDA began releasing sterile flies over the area on June 4. These missions will disperse 2 million sterile screwworms twice a week to disrupt the pest’s lifecycle.
In addition to aerial releases, USDA is shipping another 4 million sterile flies per week to Texas. These will be deployed using 24 ground release chambers, strategically placed in and around the detection zone to maximize impact.
