The Food and Drug Administration announced on October 16, 2025, the availability of final Guidance for Industry #299, titled "Dual Labeling for Fully Approved and Conditionally Approved New Animal Drugs With a New World Screwworm-Related Indication." This development allows sponsors of new animal drugs to include both fully approved and conditionally approved indications on the same product label, specifically when adding a claim related to treating or preventing New World screwworm myiasis. Published in the Federal Register Volume 90, Number 198, the notice highlights the urgency of addressing an emerging parasitic threat approaching the U.S. border. By enabling this dual labeling approach, the FDA aims to expedite the availability of effective treatments for a pest eradicated from North America decades ago but now posing risks to livestock, food security, and national interests.
Background on New World Screwworm
New World screwworm, scientifically known as Cochliomyia hominivorax, is a parasitic fly that infests warm-blooded animals by laying eggs in open wounds or mucous membranes. The larvae feed on living tissue, causing a condition called myiasis, which can lead to severe injury or death if untreated. As noted in the Federal Register notice, this pest affects livestock, pets, wildlife, and occasionally birds or humans. Eradicated from North America and Central America in previous decades through concerted efforts, the screwworm has been progressing northward since 2022 and is nearing the U.S. border with Mexico.
The notice emphasizes the parasite's potential impacts, stating it "poses an emerging threat to livestock and food security, with potential impacts on both national security and animal health." This resurgence has prompted the FDA to act swiftly, recognizing the need for rapid review and approval of animal drugs to combat infestations. The guidance specifically targets indications for treating or preventing New World screwworm myiasis, reflecting concerns over a possible public health emergency.
Overview of Guidance #299
Guidance #299 provides a framework for dual labeling, where a single product label can include an intended use fully approved under section 512(b) of the Federal Food, Drug, and Cosmetic Act (FD&C Act) and another use conditionally approved under section 571. Conditional approval allows drugs to reach the market faster for certain unmet needs, provided they meet safety and manufacturing standards, with full effectiveness data submitted later.
The FDA issued this guidance without prior public comment, invoking its good guidance practices regulation under 21 CFR 10.115(g)(2). The agency determined that such participation was not feasible due to the "significant potential for a public health emergency associated with New World Screwworm." This expedited process underscores the immediacy of the threat, as the notice explains: "In order to respond effectively and efficiently to this threat, FDA must act expeditiously to review and, where appropriate, approve or authorize animal drugs for NWS myiasis."
The guidance applies to new animal drugs already approved for other indications under section 512, allowing sponsors to add a conditionally approved New World screwworm claim. It does not cover emergency use authorizations under section 564 of the FD&C Act, focusing instead on standard and conditional approvals.
Legal and Regulatory Basis
The foundation for dual labeling stems from section 571(f)(2) of the FD&C Act, which permits the FDA to establish conditions for including conditionally approved uses on labels alongside fully approved ones through regulation or guidance. The notice clarifies that while broader guidance on dual labeling is planned for the future, this specific document addresses New World screwworm due to the "imminent health threat."
This approach aligns with existing FDA collections of information under the Paperwork Reduction Act, approved by the Office of Management and Budget. Collections related to sections 512 and 571 are covered under OMB control number 0910-0032, and those for 21 CFR 514.80 under 0910-0284. The guidance does not introduce new information requirements but refers to these established processes.
From a legal perspective, this builds on precedents for conditional approvals, introduced in 2004 amendments to the FD&C Act to facilitate faster access to drugs for minor species or minor uses. Perspectives on this mechanism vary: proponents argue it accelerates innovation for niche threats like New World screwworm, while critics may express concerns about potentially lower initial evidence standards for effectiveness, though safety remains non-negotiable.
Implications for Stakeholders
For animal drug sponsors, the guidance offers a streamlined path to expand product indications without separate labeling, potentially reducing costs and speeding market entry. Veterinarians and livestock producers gain access to multifunctional drugs, enhancing their ability to manage infestations amid the screwworm's northward advance.
Broader implications include bolstered preparedness for zoonotic threats, as New World screwworm can rarely affect humans. The notice highlights risks to national security and food supply, suggesting potential economic fallout from widespread livestock losses. Different stakeholders view this differently: agricultural groups may welcome the proactive stance, while animal welfare advocates could emphasize the need for humane treatment options. Public health experts might focus on surveillance and prevention, given the parasite's history of eradication through sterile insect techniques and other methods.
The guidance's immediate effect, as per FDA's statement, "represents the current thinking of FDA" but is not binding, allowing alternative approaches if they comply with statutes.
In conclusion, Guidance #299 marks a targeted response to an escalating animal health crisis, facilitating dual labeling to combat New World screwworm. Key next steps could involve sponsors submitting applications for conditional approvals, ongoing monitoring of the parasite's spread, and potential future expansions of dual labeling policies. Challenges include ensuring robust post-approval data collection for conditional claims and balancing urgency with rigorous standards. Debates may continue on the role of conditional approvals in addressing rare but severe threats, influencing how the FDA adapts to similar emergencies in veterinary medicine.