The New World screwworm fly, a flesh-eating parasite long eradicated from the United States, has been detected in Texas for the first time since 1966, according to the United States Department of Agriculture (USDA). The infestation was confirmed on 3 June 2026 in a three-week-old calf near La Pryor, approximately 50 miles from the Mexico border. Authorities established a 12-mile quarantine zone on 4 June to contain the outbreak and are intensifying control measures to prevent further spread.
Containment Measures And Official Response
The USDA is releasing millions of sterile screwworm flies in an effort to disrupt the breeding cycle of the parasite, a method that proved successful in the past. Additionally, 8,000 traps have been deployed and more than 77,000 samples tested across the affected area. A fruit-fly facility in southern Mexico is being converted for screwworm control at a cost of $21 million, and construction of a new $750 million screwworm factory has commenced in Texas to bolster eradication efforts.
Dudley Hoskins, Under Secretary for Marketing and Regulatory Programmes at USDA, stated, “USDA invested heavily in the tools needed to eliminate NWS ever since cases started increasing in Central America and Mexico. The United States has defeated this pest before, and we will do it again.” U.S. Secretary of Agriculture Brooke Rollins emphasised the severity of the situation, saying, “There is no doubt that this is a very, very serious threat to our livestock.”
Regional Context And Potential Impact
The New World screwworm fly’s larvae consume the living flesh of warm-blooded animals, causing potentially fatal wounds and substantial economic losses for livestock producers. While the parasite does not pose a risk to food safety, it can also infect humans in rare cases—since its re-emergence in Central America and Mexico, over 171,000 animals and 2,000 people have been affected, with ten human deaths reported according to official data.
The reappearance in Texas follows the November 2024 detection in Mexico, which marked the first major spread northward after decades of containment at the southern end of Panama. The rapid US response aims to avoid a repeat of historical outbreaks and underscores the challenges in preventing cross-border pest incursions. South African agricultural authorities are monitoring the situation closely, as the movement of livestock and increased global trade can heighten risks for regions previously declared screwworm-free.
Surveillance and sterile fly releases will continue in affected border regions as construction of the new control facilities progresses. Authorities are expected to review and expand quarantine zones depending on further findings, with ongoing monitoring for cases in both animals and humans.