A Longstanding Screwworm Defense, Renewed
After decades of absence, New World screwworm is once again drawing serious attention across the Southeast. Eradicated from the continental United States years ago, the pest resurfaced in Mexico in late 2024 and has since become a renewed concern for livestock health officials, particularly in warmer, humid climates.
Response efforts are ramping up. Treatment and prevention options have expanded with emergency approval of macrocyclic lactone products including Ivomec® (ivermectin) and Dectomax® (doramectin). ExZolt Cattle-CA1® (fluralaner) has also received conditional approval as a topical solution for prevention and treatment. Use of these products may occur under veterinary guidance and, in some cases, extra label drug use provisions.
In mid February, USDA opened a sterile fly dispersal facility in Edinburg, Texas, allowing distribution of millions of sterile male flies to strengthen the biological barrier. Plans for a nearby $750 million production plant capable of producing up to 300 million sterile flies per week, along with up to $100 million in research funding through the USDA NWS Grand Challenge, underscore a coordinated push to protect domestic livestock.
