Cochliomyia hominivorax worm infestation spreads across Mexico and reaches the United States

The larval form of the screwworm fly, Cochliomyia hominivorax, re‑emerged in Mexico in November 2024 after decades of control. Initial detection in a bovine in Chiapas triggered a nationwide veterinary emergency, and by early 2025 more than 28,000 cases had been recorded across multiple Mexican states, affecting cattle, horses, sheep, goats, dogs, cats and wildlife.

The outbreak prompted temporary closure of the cattle‑livestock border with the United States and new movement restrictions for live animals in Texas and New Mexico. U.S. health authorities confirmed infections, reactivating joint monitoring and control measures. Mexican officials have intensified surveillance, sanitary fences, and public‑awareness campaigns, including a municipal briefing in Zimapán that educated livestock producers and veterinarians about treatment and prevention of myiasis.

The situation has revived the sterile‑insect technique, a biocontrol program once hailed as a major North‑American success, as both nations work to curb further spread toward Central America.