US Livestock on Alert: Deadly Screwworm Pest Reaches Just 25 Miles From Border
The USDA has intensified emergency defenses as New World screwworm advances toward the U.S., raising concerns for livestock producers and trade.
The U.S. Department of Agriculture (USDA) announced Tuesday that the closest confirmed case of New World screwworm (NWS) has been detected just 25 miles south of the U.S. border in the Mexican state of Coahuila. The development prompted Agriculture Secretary Brooke Rollins to outline expanded federal efforts to prevent the destructive livestock pest from entering the United States, a threat that could have major economic consequences for ranchers, producers, and the broader agricultural sector.
Livestock Industry Faces Growing Biosecurity Threat
Although officials stressed that New World screwworm poses minimal risk to humans, the parasite remains a serious concern for livestock producers. The pest spreads when adult flies lay eggs in open wounds on animals, where the larvae feed on living tissue, causing severe injuries and potentially death if left untreated.
Brooke Rollins discusses the New World screwworm threat near the U.S. border. (Photo: USDA)
"The threat to the U.S. livestock industry is real," Rollins said during a USDA press briefing, defending the decision to keep the U.S.-Mexico border closed to live-animal imports since July 2025. According to USDA estimates, the pest may have already crossed into the United States last year had those restrictions not been implemented.
Since New World screwworm emerged as a significant concern in late 2024, federal authorities have dramatically expanded surveillance operations along the southern border. These efforts include additional inspection checkpoints, specially trained detection dogs, increased wildlife monitoring, and the deployment of more personnel dedicated to identifying infestations before they reach U.S. territory.
Sterile Fly Strategy Remains the Primary Defense
USDA officials emphasized that the cornerstone of the eradication strategy remains the Sterile Insect Technique (SIT), a proven method used successfully against New World screwworm for decades.
The process involves releasing millions of sterile male flies into affected regions. Because female screwworm flies typically mate only once during their lifetime, mating with sterile males prevents reproduction and gradually eliminates wild populations.
The strategy has a long track record. It helped eradicate the pest from the United States during the 1950s and was successfully deployed again following an isolated outbreak in Florida's Keys in 2016.
According to USDA Under Secretary Dudley Hoskins, New World screwworm is not contagious between animals and does not present a food safety risk, but controlling animal movement remains critical to preventing further spread.
Animal Movement Drives Most New Cases
Federal officials say recent outbreaks in Mexico appear to be linked primarily to the movement of infested animals rather than long-distance migration of the flies themselves.
Rear Admiral Michael Schmoyer, Associate Administrator at USDA's Animal and Plant Health Inspection Service (APHIS), noted that many of the newest detections have occurred within areas already receiving sterile fly releases.
This trend suggests that while eradication efforts are reducing fly populations, infected livestock continue transporting the parasite into previously unaffected areas.
As a result, USDA officials indicated that reopening the border to live-animal imports will require a comprehensive and coordinated eradication strategy throughout Mexico rather than improvements limited to specific states or regions.
Texas Prepares for Potential Arrival
State officials in Texas are working closely with federal agencies to ensure rapid response capabilities if New World screwworm reaches U.S. soil.
Bud Dinges, Executive Director of the Texas Animal Health Commission, urged livestock owners to remain vigilant.
"Monitor all wounds and contact a veterinarian immediately if you suspect New World screwworm," Dinges said, emphasizing that early detection could significantly reduce the impact of a potential outbreak.
Authorities have already installed approximately 8,000 fly traps along the border region and analyzed more than 58,000 fly samples, all of which have tested negative for New World screwworm to date.
Massive Investment in Eradication Infrastructure
To strengthen long-term containment efforts, governments across the region are investing heavily in sterile fly production capacity.
Currently, a facility in Panama produces roughly 100 million sterile flies per week. A new facility in Metapa, Mexico, is expected to begin operations this summer and could add another 60 million to 100 million sterile flies weekly.
Meanwhile, construction continues at Moore Air Base in Edinburg, Texas, where a new production center is scheduled for completion in late 2027. Once fully operational, the facility is expected to generate up to 300 million sterile flies per week, dramatically increasing North America's ability to respond to future outbreaks.
For U.S. cattle producers, ranchers, and agricultural policymakers, the latest detection serves as a stark reminder that biosecurity threats remain one of the industry's most significant challenges. With the parasite now just 25 miles from American territory, USDA officials say surveillance, containment, and rapid response efforts will remain at maximum intensity.
"We will not rest until New World screwworm is eradicated," Rollins concluded.
