U.S. moves to import Brazilian screwworm treatment for stockpile

VERSION 2 — FULL ANALYSIS

U.S. regulators are preparing to import a New World screwworm treatment from Brazil as part of the federal response to the parasite’s return. APHIS said EPA granted a Section 18 emergency exemption allowing importation and use of Elanco’s Tanidil, a topical powder intended to prevent or treat New World screwworm in livestock and other animals. The product is not currently sold in the United States, so APHIS said it now has to place an order, import the product, and relabel it, a process expected to take about 90 to 100 days. (aphis.usda.gov)

The exemption lands in the middle of a fast-moving year for screwworm preparedness and response. USDA confirmed the first U.S. case in nearly 60 years on June 3, 2026, in a calf in Zavala County, Texas. Texas officials had already been preparing for northward spread after Mexico reported progressive movement of the parasite following a November 2024 detection in Chiapas. Texas says sterile fly dispersal, surveillance, epidemiologic investigations, and movement controls are all now part of the response framework. (direct.aphis.usda.gov)

APHIS’s announcement makes clear that Tanidil is not being opened up as a standard market product for everyday prescribing. Instead, it will be held in the National Veterinary Stockpile and distributed only through APHIS, in coordination with state animal health officials and federally recognized tribal agencies. If a U.S. incursion occurs, use is limited to federal, state, local, and tribal agencies, plus people working under their supervision. APHIS also noted that some states require their own registration, which means the product may not be available everywhere even after importation is complete. (aphis.usda.gov)

That distinction matters because the broader New World screwworm drug landscape is still evolving. FDA told veterinarians in a June 5 letter that no animal drug has full FDA approval for New World screwworm myiasis, and that the agency has been using conditional approvals and emergency use authorizations to expand access. FDA’s current veterinary resource page lists a growing menu of products across species, including options for cattle, horses, dogs, cats, sheep, swine, goats, camelids, deer, and some wildlife. Negasunt Powder, another Elanco product, is already listed by FDA under emergency use authorization for prevention and treatment in multiple species, while Tanidil is arriving through the separate EPA emergency exemption route because it is a pesticide product rather than an FDA-approved animal drug. That last point is an inference based on the agencies’ different regulatory pathways. (fda.gov)

Expert commentary has been notably consistent: this wasn’t unexpected, but it still changes the operating environment for veterinarians. NC State parasitologist Andy Moorhead said specialists had been watching screwworm move northward since 2023 and were not caught off guard when it crossed into the U.S. He also emphasized that the parasite is familiar, not novel, and that eradication tools already exist, especially sterile insect technique. Texas animal health guidance echoes that point, describing sterile male release as the core eradication method because female screwworm flies mate only once. (cvm.ncsu.edu)

Why it matters: For veterinary professionals, the Tanidil decision is less about adding one more product to the shelf and more about showing how aggressively federal agencies are trying to close operational gaps before wider spread. A stockpiled, agency-controlled topical treatment could be useful in field responses where rapid wound treatment and prevention are needed across livestock or wildlife populations, especially if cases appear in areas with limited commercial options. At the same time, the patchwork of EUAs, conditional approvals, stockpile-only products, state registrations, and movement restrictions means veterinarians need to stay current on what is actually available, for which species, under what authority, and with what reporting obligations. FDA has explicitly told veterinarians this is “uncharted territory,” and Texas continues to stress that suspected cases are reportable within 24 hours. (fda.gov)

There’s also a practical surveillance message here. APHIS approved release of New Mexico’s only infested zone on August 30 and two Texas infested zones on August 31, suggesting some response measures are working. But Texas still reports 17 counties with cases and 40 premises with cases on its current response page, underscoring that the outbreak is not over. For clinicians, especially in border and movement-linked regions, vigilance around wound inspection, larval identification, sample submission, and client communication remains as important as drug access. (aphis-prod.azureedge.us)

What to watch: The next key milestones are whether APHIS completes importation and relabeling on schedule, whether states quickly grant any needed registrations, and whether additional cases near or beyond current response zones force broader deployment of Tanidil from the National Veterinary Stockpile. (aphis.usda.gov)