The U.S. has closed its southern border again to livestock imports, saying a flesh-eating parasite has moved further north in Mexico than previously reported.
Mexico’s president was critical Thursday, suggesting that the U.S. is exaggerating the threat to its beef industry from the parasite, the New World screwworm fly. The female flies lay eggs in wounds on warm-blooded animals, hatching larvae that are unusual among flies for feeding on live flesh and fluids instead of dead material.
In Mexico, President Claudia Sheinbaum said authorities there were following all established protocols to deal with the northernmost case. Mexican authorities said the country has 392 infected animals, down nearly 19% since June 24.
“From our point of view, they took a totally exaggerated decision to closing the border again,” Sheinbaum said. “Everything that scientifically should be done is being done.”
Three weeks ago, Rollins announced plans for combating the parasite that include spending nearly $30 million on new sites for breeding and dispersing sterile male flies. Once released in the wild, those males would mate with females, causing them to lay eggs that won’t hatch so that the fly population would die out.
The USDA hopes a new fly factory will be operating in southern Mexico by July 2026 to supplement fly breeding at an existing complex in Panama. The agency also plans to open a site in southern Texas for holding sterile flies imported from Panama, so they can be released along the border if necessary.
Also Thursday, U.S. Reps. Tony Gonzalez, of Texas, and Kat McCammack, of Florida, urged the Trump administration to quickly approve the use of existing anti-parasite treatments for New World screwworm fly infestations in livestock. They said labeling requirements currently prevent it.
