US reopens border woes as parasite spreads through Mexico

In early July 2025, the United States implemented a new closure of its southern border to livestock imports due to concerns over a flesh-eating parasite known as the New World screwworm fly, which has been reported moving farther north in Mexico than previously documented. This decision came after the U.S. Department of Agriculture identified an infestation located 185 miles northeast of Mexico City, significantly closer to the Texas border than prior cases had indicated. The country had initially restricted the import of live cattle, horses, and bison in May 2025 following the discovery of the parasite late in 2024. The New World screwworm fly poses a substantial threat to livestock, as the larvae it produces feed on live flesh and fluids, resulting in severe economic consequences for affected industries. Historically, the pest was largely eradicated in the 1970s through targeted sterilization programs, but recent developments have raised alarms among American officials, especially regarding potential outbreaks in Texas, which could lead to significant financial losses similar to those experienced during previous infestations. Despite the U.S. taking precautionary measures, including increased monitoring and a commitment to funding nearly $30 million toward breeding sterile male flies to combat the parasite, skepticism has arisen. Mexico's President Claudia Sheinbaum critiqued the U.S. decision to close the border again, calling it exaggerated and asserting that Mexican authorities were effectively managing the containment of the infection, with reported cases declining since late June. Furthermore, U.S. Representatives Tony Gonzalez and Kat McCammack have called for expediting the approval of existing anti-parasite treatments, indicating potential challenges regarding regulatory hurdles within veterinary practices. The complexities surrounding the New World screwworm fly situation illustrate the delicate balance of agricultural trade relations between the U.S. and Mexico, as both countries navigate biosecurity concerns and the economic implications of livestock health.