The New World screwworm, which had primarily been contained in South America, has breached the geographic barrier of the Darién Gap, with the first U.S. case since the 1960s confirmed in a calf near La Pryor, Texas, on June 3. The parasite has advanced over 1,000 miles in roughly four years, moving through Central America, Mexico, and now into Texas. As of June 17, 12 U.S. cases have been confirmed, with Mexico reporting 1,921 active cases, 50 of which are within 100 miles of the U.S. border.
The U.S. Department of Agriculture (USDA) is allocating $105 million to 40 projects under its "New World Screwworm Grand Challenge" to combat the spread. This funding will support research and other efforts. The USDA reviewed 226 applications requesting $664 million in total funding for this initiative. Canada has banned the import of livestock from Texas, and at least 12 U.S. states have imposed quarantines and movement restrictions, including Texas with 13 infested counties under quarantine.
The primary strategy to combat the screwworm involves the release of sterile male flies, which was successful in eradicating the parasite from the U.S. in the 1960s. A plant in Panama produces about 100 million sterile flies weekly, and a new $750 million U.S. plant at Moore Air Base in Edinburg, Texas, is expected to produce 100 million weekly by late 2027, with a target of 300 million. The USDA has already released 131 million sterile male screwworms into Texas in preparation for the current outbreak. Experts warn that a widespread outbreak could cost the Texas economy approximately $1.8 billion annually due to livestock deaths and related expenses.
