A New World screwworm (NWS) infestation was confirmed in a calf in Zavala County, Texas, on June 3, 2026, marking the first detection of the devastating parasite in the United States in six decades. This re-emergence follows the breach of a long-standing biological barrier at the Darién Gap in Panama in 2023, which allowed screwworm cases to surge northward through Central America and Mexico. The U.S. Department of Agriculture (USDA) and partner agencies have initiated a comprehensive, five-pronged strategy to combat the spread.
Historically, the U.S. successfully eradicated the screwworm in 1966 using the Sterile Insect Technique (SIT), a method involving the release of sterile male flies to prevent reproduction. This achievement was maintained for decades through a collaborative effort with Panama, known as COPEG (Panama-United States Commission for the Eradication and Prevention of Screwworm), which established a biological barrier at the Darién Gap. The barrier protected North and Central America from screwworm populations endemic to South America.
However, the protective barrier was breached in 2023, leading to a rapid northward progression of the pest through Central American nations. By late 2024 and early 2025, cases were confirmed in Mexico, raising alarms about potential U.S. entry. Factors contributing to the breach are believed to include interruptions in sterile fly production due to the COVID-19 pandemic and increased illegal cattle trafficking through the region.
In response to the escalating threat, the USDA has allocated significant resources to new eradication methods and sterile fly production. By summer 2025, the USDA began investing heavily in expanding sterile fly infrastructure, with plans to produce approximately 500 million sterile flies per week. This substantial funding supports the "five-pronged approach" aimed at pushing the pest back and bolstering defenses along the U.S.-Mexico border.
Amidst these developments, a social media post from "Reddit Lies" on June 6, 2026, addressed public speculation regarding the screwworm's re-emergence. The post countered claims that funding cuts by "DOGE" in March 2025 to a UN fund for screwworm monitoring were responsible for the crisis. According to the tweet, these cuts did not affect the USDA's sterile insect production or COPEG, and the subsequent massive U.S. initiative suggests any reduction in visibility into Central American screwworm activity had no negative effect on the overall response.
