Overview
- The parasite returned to U.S. livestock in early June with detections concentrated in Texas and a single inactive case in New Mexico, and case growth has slowed to fewer new infections in mid-July.
- By mid-July federal and state teams have released hundreds of millions of sterile male flies to interrupt screwworm reproduction while scaling up production in Mexico and planning a larger U.S. facility.
- Experts estimate roughly 500 million sterile flies per week are needed for effective suppression but current multinational output is far lower, creating a persistent capacity gap.
- Trade and movement controls are tightening: Canada paused many animal imports from Texas and Mexican authorities in Chihuahua set ring‑control zones, ivermectin requirements, inspections, and local quarantines.
- Officials say human risk is low, veterinarians urge daily checks of animals and prompt treatment of wounds, and some officials are urging immediate use of a tested adult‑suppression bait (SWASS) to speed short‑term control.