The United States Department of Agriculture has confirmed a total of 50 cases of New World screwworm this season, with 48 located in Texas and the remaining two in New Mexico. The latest detection involved a horse in Grant County, marking only the second New Mexico incident since the parasite resurfaced this summer. Federal officials say the northward advance is slowing, yet the risk to livestock, wildlife, and even humans remains tangible.
In response, the USDA reports that more than 1 billion sterile flies have been released across Texas since February. The agency plans to boost production to 500 million sterile flies per week by the following summer, a scale comparable to the effort that eradicated the pest from the United States decades ago. Agriculture Secretary Brooke Rollins underscored progress while warning that “we’re not out of the woods yet,” highlighting Arizona and New Mexico as zones of continued vigilance.
Sterile insect technique and nationwide coordination
The cornerstone of America’s fight is the sterile insect technique (SIT). By mass-rearing male screwworm flies, sterilizing them, and releasing them into the environment, females that mate with these males produce no offspring, gradually collapsing the wild population. This method succeeded in eliminating the parasite from the continental United States in the 1980s and remains the most effective tool available.
USDA’s Animal and Plant Health Inspection Service has established a dedicated New World Screwworm Directorate to synchronize efforts across federal, state, tribal, and local partners. Surveillance stations along the U.S.–Mexico border continuously monitor for adult flies, while joint protocols with Mexican authorities ensure rapid reporting and coordinated trap deployment. Recent funding via the NWS Grand Challenge makes up to $100 million available for research that enhances sterile-fly production, improves detection methods, and strengthens
Impact on livestock, wildlife and travel guidance
The parasite’s larvae feed on living tissue, unlike ordinary maggots that consume decay. When a female lays eggs in an open wound, the hatched larvae burrow, causing swelling, foul-smelling discharge, and potentially fatal infections. Species at risk include cattle, horses, sheep, goats, pigs, deer, and even companion animals such as dogs. Human cases are rare but can occur when untreated wounds are exposed in infested regions.
Travelers heading to affected Central American nations are advised to keep wounds clean, use insect repellent, wear long-sleeved clothing, and sleep in screened rooms or under bed nets. Pets and service animals must meet strict USDA and CDC import requirements before entering the United States. Owners should inspect wounds on livestock or pets promptly and contact a veterinarian if larvae are observed. Texas animal-health officials have begun lifting movement restrictions in previously quarantined counties—Gillespie, Kerr, Kimble, La Salle, and Webb—while urging continued vigilance.
Research breakthroughs and future outlook
At Texas Biomed in San Antonio, the company Flyttr is using a high-containment laboratory to develop next-generation sterile flies engineered to outcompete wild males even more effectively. This research, part of a broader public-private effort, aims to sustain eradication momentum and prevent re-introduction from neighboring countries where the pest persists.
While the current outbreak appears contained, experts stress that the parasite’s presence in Central and South America means the threat can re-emerge. Ongoing border surveillance, expanded sterile-fly production, and rapid‐response coordination remain essential to safeguard the nation’s $200 billion livestock industry, protect wildlife, and maintain the safety of the food supply.
