FDA authorized two F10 insecticide products for emergency use against New World screwworm: a topical spray and an ointment about a month later, on April 24, 2026. They cover livestock, horses, exotic mammals and birds; no medicated feeds for screwworm are approved in the U.S.
The emergency pathway followed an August 2025 determination by the HHS secretary that screwworm posed a substantial threat to public health and security. Ivermectin and doramectin have sometimes been given orally in federal or state parasite-control programs, but their safety and effectiveness against screwworm remain unclear for broader use; U.S. law bars animal drugs in feed for unapproved purposes.
The FDA has urged judicious use to limit resistance, especially in food animals, and emphasized that meat, milk and eggs from treated animals must not contain unsafe drug residues. In January 2026, it listed priority data gaps and sought safety and effectiveness information from academic, industry and federal partners; it cannot fund that research but offers technical support.
