FDA Issues Emergency Use Authorization for Negasunt Powder to Prevent and Treat New World Screwworm
Summary
The FDA issued an Emergency Use Authorization (EUA) for Negasunt Powder (coumaphos, propoxur, and sulfanilamide topical powder) for the prevention and treatment of New World screwworm (NWS) myiasis in cattle, swine, goats, sheep, horses, donkeys, domestic hybrid equids, and captive wild, exotic, and zoo mammals. The authorization limits distribution to the USDA and authorized federal, state, local, and tribal agency personnel prior to an NWS incursion, with additional provisions for licensed veterinarians in infested zones after an incursion. The EUA includes a boxed warning for neurotoxicity risks from coumaphos and propoxur, specific human and animal safety requirements, and food safety restrictions including a 28-day slaughter withdrawal and prohibition on use in dairy animals. Elanco US Inc. sponsors the product.
“The FDA has concluded that based on the scientific evidence available, it is reasonable to believe that Negasunt Powder may be effective for the prevention and treatment of NWS myiasis in cattle, swine, goats, sheep, horses, donkeys, domestic hybrid equids (e.g., mules), and captive wild, exotic, and zoo mammals, and that the known and potential benefits of the product outweigh its known and potential risks.”
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What changed
The FDA issued an Emergency Use Authorization for Negasunt Powder, a topical powder combining coumaphos, propoxur, and sulfanilamide, specifically for prevention and treatment of New World screwworm myiasis in multiple animal species. The authorization establishes a tiered distribution system: prior to NWS incursion in the U.S., the product is limited to federal, state, local, and tribal agency employees and those working under their authority; after an incursion, licensed veterinarians in USDA-defined infested and surveillance zones may also use the product. The EUA includes a boxed warning regarding neurotoxicity risks from two active ingredients and mandates compliance with specific safety and disposal protocols.
Affected parties—including animal health authorities, livestock producers, and licensed veterinarians in potential NWS response zones—must adhere to strict food safety restrictions: a 28-day slaughter withdrawal for treated animals, no use in dairy animals, and exclusion of treated calves and calves born to treated cows from veal processing. Elanco US Inc. intends to limit initial distribution to the USDA, making the product available primarily through official response channels rather than open commercial channels.
What to do next
- Review all human and animal safety information, including the boxed warning and limitations of authorized use
- Closely follow conditions of use and disposal instructions as detailed in the Fact Sheet
- Do not slaughter treated animals for human consumption within 28 days of the last treatment
- Do not use in animals producing milk for human consumption
Archived snapshot
Apr 27, 2026GovPing captured this document from the original source. If the source has since changed or been removed, this is the text as it existed at that time.
April 27, 2026
Today, the U.S. Food and Drug Administration issued an Emergency Use Authorization (EUA) for Negasunt Powder (coumaphos, propoxur, and sulfanilamide topical powder) for the prevention and treatment of New World screwworm (NWS) infestations (myiasis).
The FDA has concluded that based on the scientific evidence available, it is reasonable to believe that Negasunt Powder may be effective for the prevention and treatment of NWS myiasis in cattle, swine, goats, sheep, horses, donkeys, domestic hybrid equids (e.g., mules), and captive wild, exotic, and zoo mammals, and that the known and potential benefits of the product outweigh its known and potential risks.
Currently, Elanco US Inc., the drug sponsor, intends to limit distribution of Negasunt Powder to the U.S. Department of Agriculture (USDA) for further distribution to authorized users. Prior to an incursion of NWS into the U.S., Negasunt Powder is only available for use by employees of federal, state, local, and federally recognized tribal agencies, and people working under their authority and at their direction. If there is an incursion of NWS into the U.S., the product may also be used by or on the order of a licensed veterinarian in NWS-infested zones and adjacent surveillance zones as defined by the USDA in the NWS Response Playbook (page 9). There are no NWS-infested zones in the U.S. because, to date, NWS is not currently in the U.S.
Coumaphos and propoxur, two of the active ingredients in Negasunt Powder, can cause neurotoxicity. The EUA sets specific requirements to address this risk for people, animals, and the environment.
It is important that authorized users of this product review all human and animal safety information, including the boxed warning and limitations of authorized use, and closely follow its conditions of use and disposal instructions as detailed in the Fact Sheet: Emergency Use Authorization of Negasunt Powder (coumaphos, propoxur, and sulfanilamide topical powder) for New World Screwworm (NWS).
Food safety information:
- Treated animals must not be slaughtered for human consumption within 28 days of the last treatment.
- A milk discard time has not been established for this product; do not use in animals producing milk for human consumption.
- A withdrawal period has not been established for this product in pre-ruminating calves; treated calves and calves born to treated cows must not be processed for veal. This EUA will be effective until it is revoked or the HHS Secretary terminates the declaration that the potential public health emergency presented by NWS justifies the emergency use authorization of animal drugs for NWS.
Negasunt Powder is sponsored by Elanco US Inc. based in Indianapolis, Indiana.
Additional Information
- Freedom of Information Summary: Negasunt Powder (EUA 006653)
- Letter of Authorization: Negasunt Powder (EUA 006653)
- Fact Sheet: Emergency Use Authorization of Negasunt Powder (coumaphos, propoxur, and sulfanilamide topical powder) for New World Screwworm (NWS)
- Animal Drugs for New World Screwworm
Content current as of:
04/27/2026
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