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U.S. Shuts Southern Border to Mexican Livestock After New Screwworm Detection

USDA is advancing a $300 million sterile-fly factory in Texas, following a $21 million renovation of Mexico’s facility to sustain weekly breeding campaigns.

A photo from 1960 shows US workers preparing sterile flies for dispersal.
Animal health worker Eduardo Lugo treats the wounds of a cow at the Chihuahua Regional Livestock Union in Nuevo Palomas, Mexico.
The adult fly form of the New World screwworm has a blue-green metallic exoskeleton.
New World screwworm fly (Cochliomyia hominivorax) on Friday, Jun 06, 2025, in College Station, Texas. (Michael Miller/Texas A&M AgriLife)

Overview

  • Secretary of Agriculture Brooke Rollins ordered an immediate halt to live cattle, bison and horse imports at southern ports after SENASICA confirmed a screwworm case in Ixhuatlán de Madero, Veracruz.
  • The shutdown reverses this week’s phased port reopenings and will remain in place until Mexico demonstrates further progress in containing the parasite.
  • USDA is fast-tracking a $300 million sterile-fly production facility at Moore Air Base in South Texas alongside a $21 million upgrade of Mexico’s breeding complex to produce hundreds of millions of sterilized male flies each week.
  • The sterile insect technique, first used to eradicate screwworm from U.S. livestock by 1966, is central to binational efforts aimed at pushing the parasite back toward the Darien Gap.
  • Officials warn that without sustained surveillance and release campaigns, a renewed outbreak could kill cattle within two weeks and inflict up to $1.8 billion in losses on the Texas livestock sector.