US halts Mexican cattle imports over screwworm outbreak Livestock trade paused as USDA warns of parasite spread10 July 2025 10 July 2025 1 minute read 1 minute read By: By: Global Ag Media North AmericaThe US Department of Agriculture has again halted imports of Mexican cattle into the United States due to the spread of the damaging livestock pest New World Screwworm in Mexico, reported Reuters. Screwworms are parasitic flies whose females lay eggs in wounds on warm-blooded animals, usually livestock and wild animals. Once the eggs hatch, hundreds of screwworm larvae use their sharp mouths to burrow through living flesh, eventually killing their host if left untreated. The decision was a quick reversal after the USDA said last week it would resume cattle imports from Mexico on Monday at a port of entry in Douglas, Arizona, as part of a phased reopening of the border. Washington suspended cattle imports from Mexico in May as New World Screwworm was detected in farms in Oaxaca and Veracruz, Mexico, about 700 miles from the US border.