On August 19, 2025, the U.S. Department of Health and Human Services (HHS) announced that the HHS Secretary had issued a declaration allowing the U.S. Food and Drug Administration (FDA) to issue Emergency Use Authorizations (EUAs) for animal drugs to treat or prevent infestations caused by the New World Screwworm (NWS), Cochliomyia hominivorax. This is the first time the HHS Secretary has issued an EUA declaration for animal drugs since the 2016 amendment of the Federal Food, Drug, and Cosmetic Act (FDCA) by the 21st Century Cures Act to permit the issuance of EUAs for animal drugs. In addition to being precedent-setting, the HHS declaration enables animal drug manufacturers to pursue EUAs for animal drugs that may be effective in treating or preventing NWS, which poses an emerging and serious threat to U.S. livestock and food security.
Background
NWS is a parasitic fly that infests warm-blooded animals, including livestock, pets, wildlife, and occasionally birds, causing severe tissue damage and sometimes death. Although NWS can also infect humans, such cases in the U.S. are rare, and HHS’s announcement confirmed that the risk to human health in the U.S. “remains very low.” NWS was eradicated from North America and Central America decades ago, but Central America and Mexico have been combating a NWS outbreak in recent years. U.S. authorities have been on high alert as NWS progresses north towards the American border with Mexico, posing a potential future threat to U.S. animal populations and the food supply. Among other actions taken to address the threat of NWS, the U.S. Department of Agriculture (USDA) announced a five-pronged plan to protect the U.S. from NWS in June 2025 and shut down U.S. southern border ports to livestock trade in July 2025. FDA’s Center for Veterinary Medicine (CVM) reports that it is working closely with USDA, the U.S. Environmental Protection Agency, other U.S. government departments and agencies, and state animal health officials to monitor and prepare for the threat of NWS.
Currently, there are no drugs approved for the treatment or prevention of NWS infestations in animals. Notably, to assist veterinarians in identifying drugs that may be prescribed for extra-label use to treat or prevent NWS infestations (to the extent permitted by FDA regulations under 21 C.F.R. Part 530), CVM recently published a webpage, titled “New World Screwworm: Information for Veterinarians,” that lists FDA-approved animal drugs labeled for indications other than NWS infestations that scientific literature indicates may be effective to prevent or treat NWS infestations. The webpage makes several disclaimers, including that FDA has not reviewed the listed drugs for the prevention and treatment of NWS infestations, that CVM is not endorsing or recommending their use for these purposes, that there are information gaps in the scientific literature about the use of animal drugs for NWS infestations, and that the information provided may not be exhaustive.
FDA’s EUA Authorities for Animal Drugs
FDCA Section 564 (21 U.S.C. § 360bbb–3), as amended by the 21st Century Cures Act, expressly permits FDA to authorize the emergency use of an unapproved new animal drug or an unapproved use of an approved or conditionally approved new animal drug after the HHS Secretary has made a declaration of emergency or threat justifying authorization of emergency use in accordance with section 564(b), i.e., an EUA declaration. Following an EUA declaration, and after consultation with the Assistant Secretary for Preparedness and Response, the Director of the National Institutes of Health, and the Director of the Centers for Disease Control and Prevention (to the extent feasible and appropriate given the applicable circumstances), FDA may issue an EUA for an unapproved new animal drug or unapproved use of an approved or conditionally approved new animal drug if FDA concludes that the relevant criteria set forth in section 564(c) of the FDCA are met. These criteria include FDA’s conclusion that:
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The chemical, biological, radiological, or nuclear (CBRN) agent referred to in the HHS declaration can cause a serious or life-threatening disease or condition;
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Based on the totality of the scientific evidence available, it is reasonable to believe that the new animal drug may be effective in diagnosing, treating, or preventing such disease or condition, and that the known and potential benefits of the new animal drug outweigh the known and potential risks; and
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There is no adequate, approved, and available alternative to the new animal drug for diagnosing, preventing, or treating such disease or condition.
An EUA declaration thus enables sponsors to submit EUA requests for unapproved new animal drugs or unapproved uses of an approved or conditionally approved new animal drug to treat or prevent serious or life-threatening diseases or conditions caused by CBRN threat agents, provided the other statutory criteria are met. FDA has issued guidance for Emergency Use Authorization of Medical Products and Related Authorities, explaining the agency’s general recommendations and procedures applicable to EUAs. Although FDA has stated that much of the guidance applies to new animal drugs, the guidance asks sponsors seeking EUA for new animal drugs “to contact FDA directly to discuss how to proceed.”
HHS Emergency Declaration for NWS
On August 18, 2025, pursuant to section 564(b) of the FDCA, HHS Secretary Robert F. Kennedy, Jr. determined that there is a significant potential for a public health emergency that has a significant potential to affect national security or the health and security of U.S. citizens living abroad and that involves NWS. Pursuant to this determination and his authority under section 564(b), Secretary Kennedy issued a declaration that circumstances exist justifying the authorization of emergency use of animal drugs to treat or prevent NWS infestation in animals. The corresponding notice HHS published yesterday in the Federal Register explains that the FDA Commissioner, Dr. Martin Makary, had specifically requested that the Secretary issue the EUA declaration to allow FDA to act quickly and take measures based on currently available information about NWS, in light of the looming threat that NWS will reach the U.S.
HHS’s announcement states that FDA will provide future guidance to veterinarians and stakeholders on the appropriate use of any EUA products and update the “New World Screwworm: Information for Veterinarians” webpage. CVM has also updated its informational webpage on NWS, titled “Animal Drugs for New World Screwworm,” with an explanation of the implications of the HHS emergency declaration for making animal drugs for NWS available. This webpage states that animal drug sponsors interested in pursuing an EUA for a drug to prevent or treat NWS should email AnimalDrugNWS@fda.hhs.gov, after which FDA will follow up with sponsors to obtain any additional information needed to assess whether the product is eligible for review under the EUA pathway for NWS.
If you have any questions concerning the material discussed in this client alert, please contact members of our Animal Food and Drug practice.
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