New World screwworm is now just 25 miles from the U.S. border. During a June 10 press conference, Agriculture Secretary Brooke Rollins said Mexican officials confirmed eight new cases of screwworm on May 31. One of those was detected in a 5-year-old goat in Coahuila, Mexico, near the Texas border.
This marks the closest reported case to the U.S. border since NWS first resurfaced in Mexico during late 2024.
Decades of eradication efforts once drove NWS out of the U.S. and Mexico, pushing it as far south as Panama. Before these efforts, screwworm outbreaks had repeatedly devastated the livestock industry throughout the early and mid-20th century.
By 1966, U.S. officials believed they had successfully eliminated the pest within U.S. borders. However, one last major U.S. outbreak occurred in the 1970s.
That outbreak cost Texas producers alone more than $132 million in 1976. According to USDA projections, a similar outbreak today would cost Texas cattle producers more than five times that amount. The estimated hit to the state’s economy could potentially top $1.8 billion.
Rollins said USDA is working to ensure that doesn’t happen.
“The New World screwworm crisis farmers and ranchers experienced back then will not repeat itself today,” she said. “Unlike then, USDA is leading a robust, detailed, technologically advanced response, paired with our plan of action going forward.”
That response, she said, will include new protocols that will be implemented “the very moment” screwworm is detected in the U.S.
USDA and relevant state-level officials will enact quarantines, movement restrictions and additional surveillance to limit the spread of a potential outbreak. Sterile flies will also be released in the immediate areas to prevent the flies from reproducing. Rollins added that USDA’s response will be “scientifically tailored” to the specific nature of any screwworm detection.
“We’re going to be ready for all scenarios. Whether it is a wild fly found in a trout, larva detected in livestock or a detection in a wild animal, we are ready,” she said.
What’s the situation in Mexico?
Rear Adm. Michael Schmoyer, who directs the New World Screwworm Directorate at the Animal and Plant Health Inspection Service, said Mexico has 1,882 active cases currently. Since late 2024, more than 26,000 cases have been confirmed in Mexico. While cases within 100 miles of the U.S. border have increased, Schmoyer noted that all of them fall within the current sterile fly dispersal zone.
Sterile files have proven to be one of the most effective methods of stopping the spread of NWS.
Schmoyer said his team continues to work closely with their Mexican counterparts to gather additional epidemiological data.
“If there was a detection in the United States, USDA will take immediate action to contain and eradicate the pest,” he said.