New World Screwworm Returns to Texas After 60 Years, Two Cases Confirmed in Five Days

The U.S. Department of Agriculture confirmed New World screwworm in a bovine in Zavala County, Texas on June 3, 2026—the first U.S. detection since 1966. A second case followed on June 5 in a calf in La Pryor. The parasite's larvae feed on living tissue and can complete a generation in roughly 21 days. The fly had been suppressed south of Panama through a decades-long sterile insect technique program. Its reappearance signals potential breach of the U.S.-Mexico-Central America containment barrier.