SCREWWORM PEST HAS ARRIVED IN THE US
The New World Screwworm (NWS) is a flesh eating fly whose larvae feed on living tissue. It was eradicated in the U.S. in the 1960s but has reemerged in Texas.
As of June 9th, there have been 5 confirmed cases in 4 Texas counties. These cases (2 calves, 1 goat and a dog from New Mexico) have been in Zavala, Webb, LaSalle and Uvalde counties, close to the US/Mexico border. In Texoma, there is no need to panic because it is not here and will not arrive any time soon. Because of the diligent USDA efforts, the arrival of the screwworm into the US from Mexico was delayed a year. So, it will not migrate up to north Texas for quite some time.
To prevent the spread, the 4 counties with confirmed cases have been quarantined for livestock movement. The USDA is currently releasing millions of sterile screwworm flies in south Texas to stop the reproduction cycle of the NWS fly and maggots. Sterile NWS male flies have been released by the USDA since 2023 on the US border, in Mexico, and Central America. It did not stop the migration from Mexico but did slow it. Live Cattle and livestock from Mexico or Central America have been prohibited or restricted from entering the US since July 2025.
The screwworm is NOT in fruits, vegetables, or processed meat so our food supply is safe. All slaughter cattle, meat, poultry are USDA inspected. Any evidence of screwworm infection in an animal would be identified with these inspections and action taken.
The screwworm fly pest can be devastating to our cattle industry in Texas causing cattle sickness and death, and quarantine of cattle in Texas closing markets and movement.
The adult screwworm fly lays eggs on live open tissue such as a newborn calf umbilicus and body openings such as the nose, ears, or genitalia, also dehorn wounds, or cuts on horses. The eggs hatch into maggots which feed on and burrow deeper into the tissue causing infection and death if not treated. Then the maggots molt into flies and start the reproducing cycle again. Wildlife such as deer can also be infected by the screwworm.
From the USDA
USDA and Texas officials are taking immediate action to contain and eradicate NWS from the US, following the strategies and actions outlined below.
-Forming a unified Incident Command Team with the Texas Animal Health Commission and deploying response personnel to the area.
-Establishing a 20 km infested zone around the detection and implementing quarantines, movement controls, and surveillance in this area.
-Expediting target release of sterile NWS flies by immediately deploying ground release chambers in the area, in addition to the 4 million sterile flies per week already being released aerially in the area..
-Increased trapping for NWS flies along the border and just outside of the dispersal area.
-Implementing NWS surveillance and management strategies in wildlife.
-Conducting targeted outreach in the local area.
“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 movement. Protecting our livestock industry is a national security issue of the utmost importance and USDA is wasting no time in taking action” said Dudley Hoskins, Under Secretary for Marketing and Regulatory Programs. “The USDA invested heavily in the tools needed to eliminate New World Screwworm ever since cases started increasing in Central America and Mexico. The United States has defeated this pest before, and we will do it again.”
Current information on the NWS can be found at Screwworm.gov
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