FDA Grants Emergency Approval for Over-the-Counter Screwworm Treatment for Pets

The FDA on June 12, 2026 granted emergency use authorization for generic nitenpyram tablets, making it the first generic animal drug cleared to treat New World screwworm, a parasitic fly whose larvae burrow into the living tissue of warm-blooded animals through open wounds or body openings. The drug, already approved under the brand name Capstar for flea treatment since 2000, kills most screwworm larvae within hours of the first dose; pet owners are instructed to administer a second dose six hours later, and a veterinarian may still need to remove remaining larvae. The authorization applies to dogs and cats weighing at least two pounds and at least four weeks old, though the drug does not prevent reinfestation. Seven confirmed U.S. cases have been identified — six in Texas and one in a dog in New Mexico — marking the parasite's first domestic detections in decades after it was thought eradicated through a major sterile fly program. Multiple states, including Idaho, Colorado, and Florida, have enacted emergency entry requirements or movement restrictions for warm-blooded animals from affected zones, and Canada has barred livestock originating in or passing through Texas within 21 days. Experts warn that a wider outbreak could further strain the U.S. cattle herd, already at its lowest level since 1951, potentially driving beef prices higher; the USDA estimates a repeat of the 1976 Texas outbreak could cause roughly $1.8 billion in economic damage. Pet owners are advised to inspect animals daily for wounds, use parasite prevention medications, and contact a veterinarian immediately if screwworm infestation is suspected.