US prepares to import New World screwworm treatment from Brazil as cases approach border

The US is preparing to bring in a treatment for New World screwworm (NWS) that is not currently available domestically, as the parasite continues to move closer to the southern border. On April 27, the US Environmental Protection Agency (EPA) granted an emergency exemption allowing the US Department of Agriculture (USDA) to import Tanidil (coumaphos, propoxur), a topical powder made by Elanco Animal Health in Brazil for multiple livestock and select wildlife species.¹ Confirmed cases of NWS have been reported within 62 miles of the US-Mexico border.

The exemption, issued at the request of USDA’s Animal and Plant Health Inspection Service (APHIS), is intended to get the product into the national veterinary stockpile before any confirmed US cases.¹ Earlier the same day, the FDA issued an Emergency Use Authorization (EUA) for a related product, Negasunt Powder (coumaphos, propoxur, and sulfanilamide), also manufactured by Elanco.²

"These emergency authorizations provide new, science-based solutions and treatment options to livestock producers, veterinarians, and other animal health industry stakeholders at a time when they need them most," said Ellen de Brabander, PhD, executive vice president of Research and Development at Elanco.³

How Tanidil differs from Negasunt

Tanidil and Negasunt share 2 active ingredients, coumaphos and propoxur, and both are applied topically to wounds to prevent or kill NWS larvae. The difference is that Negasunt also contains sulfanilamide, an antibiotic, which places it under FDA oversight. Tanidil, which does not contain an antibiotic, is regulated as a pesticide by the EPA instead.^1,3

Both products will be available only through APHIS' National Veterinary Stockpile and will be distributed with state animal health officials and federally recognized tribal agencies.

Tanidil is authorized for use in livestock, captive and temporarily captured wildlife, and select zoo species, but is not approved for use in domestic pets or birds.¹

When will it be available?

A key logistical hurdle remains. Once APHIS places an order, importation and relabeling are expected to take approximately 90 to 100 days.¹

State-level requirements may add further delays. Some states require their own pesticide registration before a product can be used within their borders. APHIS said it will notify states of the exemption and request registration where needed, meaning availability may vary by state, particularly early on.¹

Who can use it

Access to Tanidil is currently limited to federal, state, local, and federally recognized tribal agency personnel, along with those working under their supervision.

If NWS is detected in the US, authorized use would expand to include veterinarians, personnel at quarantine stations, certified applicators at livestock and game facilities, zoo and wildlife facility staff, animal rehabilitation centers, and other wildlife professionals, according to the USDA.¹

Both coumaphos and propoxur carry neurotoxicity risks, and the product includes a boxed warning addressing safety for people, animals, and the environment.^1,2 APHIS said it will provide additional guidance on tracking, reporting, and required personal protective equipment once the product is imported.

The exemption took effect April 27, 2026, and expires April 27, 2029.³ Additional updates will be posted at Screwworm.gov as they become available.

References

1. USDA Highlights EPA Emergency Exemption of Product To Treat New World Screwworm. News release. US Department of Agriculture Animal and Plant Health Inspection Service. April 27, 2026. Accessed April 28, 2026.
2. Bautista-Alejandre A. FDA authorizes Negasunt Powder for New World screwworm under emergency use. dvm360. April 27, 2026. Accessed April 28, 2026. https://www.dvm360.com/view/fda-authorizes-negasunt-powder-for-new-world-screwworm-under-emergency-use
3. Elanco's Negasunt™ Powder (Coumaphos, Propoxur, Sulfanilamide Topical Powder) and Tanidil™ (Coumaphos, Propoxur) Receive Emergency Authorization for Use Against New World Screwworm in Livestock. News release. Elanco Animal Health. April 27, 2026. Accessed April 28, 2026. https://prnmedia.prnewswire.com/news-releases/elancos-negasunt-powder-coumaphos-propoxur-sulfanilamide-topical-powder-and-tanidil-coumaphos-propoxur-receive-emergency-authorization-for-use-against-new-world-screwworm-in-livestock-302754870.html