Screwworm Halts Mexican Livestock Exports, Impacting Meat Producers

In July 2025, the United States Department of Agriculture (USDA) reimposed the border closure on the import of cattle, bison, and horses from Mexico after confirming a new case of screwworm (Cochliomyia hominivorax) in Veracruz. This parasitoid insect, whose larvae feed on living tissue, triggers serious diseases (myiasis) that threaten livestock productivity, directly impacting logistical costs, animal health, and the dynamics of binational trade. What is the screwworm and why is it so dangerous? The screwworm, known in English as the "New World screwworm fly" (Cochliomyia hominivorax), is a dipteran whose larvae parasitize the living tissue of warm-blooded animals, including cattle. The female deposits between 250 and 500 eggs in fresh wounds, and within a few days the larvae actively feed, causing tissue damage, triggering secondary infections, and even animal death. Historically, the U.S. and Mexico successfully implemented the sterile insect technique (SIT) between the 1950s ...