U.S. adds screwworm treatments as cases near the border: full analysis

The U.S. is widening its treatment toolkit against New World screwworm as the parasite edges closer to the southern border. On April 27, 2026, EPA granted USDA a Section 18 emergency exemption to import Tanidil from Brazil, while FDA issued an emergency use authorization for Negasunt Powder for prevention and treatment of screwworm myiasis in multiple animal species. The move gives federal and state responders another option to stockpile ahead of any U.S. incursion, even though USDA says New World screwworm is not currently present in the United States. (aphis.usda.gov)

The regulatory actions are part of a larger federal push that has accelerated over the past year. In August 2025, HHS declared that circumstances justified emergency use authorizations for animal drugs targeting New World screwworm, opening the door for FDA to authorize unapproved products or uses. Since then, USDA has expanded surveillance, shifted sterile fly dispersal efforts toward the U.S. border, and launched a dedicated screwworm information hub. APHIS announced in January 2026 that it was redirecting its 100 million-per-week sterile fly dispersal effort to include operations roughly 50 miles into Texas along the Tamaulipas border. (fda.gov)

The immediate trigger is the northward spread of cases in Mexico. CDC warned in January that New World screwworm cases had reached Tamaulipas, the Mexican state bordering Texas, and said more than 1,190 human cases and seven deaths had been reported across Central America and Mexico as of January 20, 2026. USDA’s current status page, last updated May 5, says the parasite is still absent from the U.S., but confirms that cases have been detected within 400 miles of the border and that all southern ports of entry are currently closed to livestock trade. (cdc.gov)

The new treatment authorizations come with important limits. APHIS says Tanidil, a coumaphos-propoxur topical powder made in Brazil, must be imported and relabeled, which is expected to take about 90 to 100 days after the official order is placed. It will be available only through APHIS via the National Veterinary Stockpile, and some states may need to complete their own registrations before the product can be used locally. FDA’s Negasunt authorization is similarly restricted: before any U.S. incursion, it is limited to federal, state, local, and tribal agencies, or people operating under their authority. If screwworm enters the U.S., Negasunt may also be used by, or on the order of, a licensed veterinarian in USDA-defined infested and adjacent surveillance zones. (aphis.usda.gov)

Industry has framed the authorizations as a readiness measure. Elanco said confirmed cases had been detected as close as 62 miles south of the U.S.-Mexico border and described the federal decisions as a way to give veterinarians and livestock producers a treatment option before the fly is detected domestically. The company also emphasized wound management and fly control as key prevention steps, noting that even small bites can create entry points for larvae. Elanco’s head of R&D, Dr. Ellen de Brabander, said the company appreciated the agencies’ “swift review” of the supporting data. (elanco.com)

Why it matters: For veterinary professionals, especially those in food animal, equine, mixed, zoo, and border-state practice, these actions signal that New World screwworm preparedness is moving from surveillance into operational planning. The details matter: these are not open-market products for routine prescribing, and their use is tied to federal response structures, authorized-user rules, and, in the case of FDA-authorized drugs, species-specific conditions and safety requirements. Practices may need to refresh foreign animal disease reporting pathways, review wound-myiasis differentials, and prepare staff to work with state animal health officials if suspicious cases emerge. The situation also has implications for companion animals and pet parents who travel internationally, because APHIS has separately issued veterinary guidance for dogs and cats moving across borders. (fda.gov)

The broader implication is that treatment access is only one layer of defense. USDA is pairing stockpiled therapeutics with border surveillance, sterile insect technique, wildlife monitoring, and trade controls, suggesting officials are trying to avoid the far more costly scenario of domestic reestablishment. For clinicians, that means early recognition and rapid reporting remain at least as important as treatment availability. A product sitting in the stockpile helps only if a suspect case is identified quickly enough to trigger containment. (aphis.usda.gov)

What to watch: The next milestones are APHIS updates on Tanidil import timing and state registrations, any expansion of authorized-use instructions for veterinarians, and whether Mexico case maps or USDA response zones shift closer to the border over the summer. (aphis.usda.gov)