New World Screwworm (NWS) Impact to U.S.

Parasite on the Brink

New World screwworm, the larva of the fly Cochliomyia hominivorax, infests open wounds on warm-blooded animals, burrowing into flesh and causing severe damage or death if untreated. Eradicated from the US in 1966 through innovative sterile insect techniques, it has staged a dramatic comeback in the Americas.

The current crisis traces to 2023, when cases exploded in Panama from an average of 25 annually to over 6,500. The parasite then marched north, overwhelming containment in Costa Rica, Nicaragua, Honduras, Guatemala, Belize, El Salvador, and into Mexico by late 2024. By February 2026, detections in Tamaulipas state—bordering Texas—numbered 11, up from three in early January, signaling an established local population.

Livestock producers in southern US states are on high alert. Texas Governor Greg Abbott declared a disaster on January 29, 2026, mobilizing resources against a threat that could mirror the 1950s epidemics, when annual US losses hit $400 million in today's dollars. Cattle, sheep, goats, horses, and even wildlife like deer face risks; a single infested animal can spread the fly rapidly.

Human cases, though rarer, add urgency. Over 1,300 infections reported in outbreak zones, including a US traveler from El Salvador diagnosed in Maryland in August 2025—the first such case in decades. Pets and birds are vulnerable too, broadening the ecological fallout.

Economic stakes are immense. The US livestock sector, valued at over $600 billion, could suffer treatment costs, animal mortality, and export bans. In Texas alone, projections estimate $732 million yearly hits to producers, cascading to $1.8 billion in wider losses. Border closures since May 2025 have idled feedlots, like Lubbock Feeders announcing shutdowns, and strained bilateral trade worth $1 billion annually at some ports.

Non-obvious tensions simmer beneath the response. Climate change, with warmer temperatures expanding fly habitats, may fuel the resurgence, alongside lapses in Panama's sterile fly program. US pressure on Mexico has escalated, with Agriculture Secretary Brooke Rollins criticizing cooperation gaps despite $21 million in aid for fly factories. A June 2025 plane crash killing crew en route to release sterile insects underscored operational hazards.

Trade-offs abound: Sterile fly dispersal, effective historically, demands massive scale—up to 100 million insects weekly from new Texas facilities opening in 2026—but risks public backlash over aerial releases. Emergency FDA approvals for preventive drugs in cattle, dogs, and cats offer short-term shields, yet long-term eradication hinges on regional coordination amid geopolitical frictions.