New World Screwworm Sparks US Import Restrictions and Mexico Trade Halt

The parasitic New World screwworm, eradicated in the United States in the 1960s, has re‑emerged north of the Mexican border. A confirmed case was found in a Texas calf, prompting the U.S. Department of Agriculture to suspend live cattle imports from Mexico and to intensify a sterile‑fly release program. USDA has allocated $21 million to convert a fruit‑fly factory in Mexico for sterile screwworm production and has opened a dispersal facility in Texas, with a second facility expected by late 2027.

In response to the threat, Wisconsin issued a temporary order requiring additional certification and permits for warm‑blooded animals imported from Texas and New Mexico, the two U.S. states with active screwworm zones. Animals from non‑infested zones must carry a Certificate of Veterinary Inspection stating they did not originate from an infested area; those from infested zones need a DATCP‑approved permit and a pre‑movement inspection.

Mexico’s agriculture ministry announced a halt to most live‑animal imports from the United States, covering cattle, horses, pigs, sheep, goats and other species, to protect its northern herds. The outbreak has already pushed beef prices higher by tightening the supply chain, with USDA estimating a potential economic impact of $1.8 billion to $8.5 billion for Texas’s livestock sector.