FDA grants EUA to F10 spray for New World screwworm: full analysis

CURRENT FULL VERSION: The FDA has authorized emergency use of F10 Antiseptic Wound Spray with Insecticide as a prevention and treatment option for New World screwworm myiasis across multiple species, giving veterinarians another tool as U.S. officials prepare for the possibility of spread from Mexico toward the southern border. The product is authorized for cattle, horses, minor species of hoof stock, raptors and other wild birds, pet birds, and captive wild, exotic, and zoo mammals. The authorization lands as the broader federal response continues to widen, with FDA also issuing an EUA for over-the-counter Ivomec (ivermectin) injectable solution for screwworm prevention in cattle and EPA granting an emergency exemption so USDA can import Tanidil, a Brazilian topical powder, into the national veterinary stockpile. (fda.gov)

The move sits within a broader federal response that accelerated in August 2025, when HHS issued a declaration allowing FDA to grant Emergency Use Authorizations for animal drugs targeting New World screwworm. FDA said at the time that there were no FDA-approved drugs for screwworm in the U.S., even as the parasite, eradicated from North and Central America decades ago, had been moving north since 2022 and was approaching the U.S.-Mexico border. Since then, FDA and USDA have been building a larger response framework that includes drug authorizations, veterinary guidance, and APHIS preparedness efforts. On the USDA side, APHIS also requested EPA’s April 27 emergency exemption to import Tanidil after confirmed screwworm cases were reported within 62 miles of the U.S.-Mexico border, with the goal of getting product into the stockpile before any confirmed U.S. detections. (fda.gov)

F10’s authorization is notable partly because it extends a product already familiar in some veterinary settings. FDA added the spray to the Index of Legally Marketed Unapproved New Animal Drugs for Minor Species in 2015 for use as a topical antiseptic for surface wounds, to repel flies, and to treat fly strike in raptors, pet birds, captive small mammals, captive reptiles, and captive exotic or zoo mammals. Under the EUA, that same spray can now be used specifically for New World screwworm prevention and treatment in a broader set of species, though FDA stresses that it has not been approved or indexed for screwworm itself. (fda.gov)

The supporting rationale is also worth noting. In its Freedom of Information summary, FDA said the sponsor’s evidence drew on data previously submitted for the indexed product, new EUA materials, and publicly available information. Much of the earlier effectiveness evidence came from blowfly species common in South Africa rather than New World screwworm directly, but FDA concluded that cypermethrin’s documented activity against several myiasis-causing flies, combined with the product’s wound antiseptic role, made it reasonable to believe the spray may be effective when applied to wounds or sites of infestation. (fda.gov)

For frontline use, the details matter. FDA says the spray is available over the counter, should be applied only to the wound site, and may be repeated weekly if needed. The agency also set food-safety restrictions: cattle, goats, and sheep treated with the product have a 30-day slaughter withdrawal, milk from cows, goats, and sheep must be discarded during treatment and for 10 days afterward, treated calves and calves born to treated cows must not be processed for veal, and the product should not be used in horses intended for human consumption. It also should not be used in domestic dogs or cats, a gap FDA has addressed separately through later screwworm EUAs for canine and feline products. Another recent FDA action added Ivomec to the cattle side of the response: the ivermectin injectable is authorized over the counter to help prevent screwworm infestations when given within 24 hours of birth, at castration, or when a wound appears. That product carries its own restrictions, including no use in female dairy cattle producing milk for human consumption, no use in calves intended for veal, and a 35-day slaughter withdrawal; FDA and sponsors have also emphasized using antiparasitics only when medically necessary as part of broader parasite-management plans to help limit resistance pressure. (fda.gov)

Industry reaction in formal quote form has been limited, but the federal message has been consistent: agencies are framing these authorizations as stopgap but necessary tools. In FDA’s August 19, 2025 announcement opening the EUA pathway, HHS Secretary Robert F. Kennedy Jr. said the step was meant to help safeguard the food supply, while USDA Secretary Brooke Rollins called emergency authorization “another tool” in the fight against screwworm. That framing fits FDA’s current veterinary guidance, which now lists multiple screwworm-related products and underscores that extralabel use does not apply to EUA products, making adherence to the fact sheet especially important in practice. On the import side, Elanco said the emergency authorizations are intended to provide new science-based treatment options as stakeholders prepare for possible U.S. cases. (fda.gov)

Why it matters: For veterinary professionals, this is less about a single product launch than about operational readiness. Screwworm response depends on early wound recognition, rapid reporting, species-appropriate treatment, movement controls, and careful attention to residue and food-animal limitations. F10 spray broadens the available topical options for mixed-species settings, including wildlife, avian, equine, and zoo medicine, where a single authorized product can simplify initial response. At the same time, the evidence base is still EUA-level, not full approval, so clinicians and animal health officials will need to balance urgency with strict compliance on species, administration, and withdrawal periods. The same is true across the growing toolbox: Tanidil and Negasunt share coumaphos and propoxur, but Tanidil lacks the antibiotic sulfanilamide that puts Negasunt under FDA oversight, so Tanidil is moving through an EPA emergency exemption instead. It is intended for livestock, captive and temporarily captured wildlife, and select zoo species—not domestic pets or birds—and, at least initially, access is limited to APHIS stockpile channels and government or supervised personnel rather than routine commercial distribution. (fda.gov)

What to watch: Expect more layering of the screwworm toolkit, not less. FDA’s current screwworm page already shows a growing list of authorized or conditionally approved products, while APHIS continues to update prevention guidance and national response planning. The next meaningful developments will likely be additional species-specific authorizations, more formal field-use guidance for veterinarians, and any shift in outbreak geography that changes how aggressively products move from preparedness stockpiles into routine deployment. For Tanidil specifically, logistics will matter: after APHIS places an order, importation and relabeling are expected to take about 90 to 100 days, and some states may require separate pesticide registration before the product can be used, which could make early availability uneven. If U.S. cases are detected, authorized use is expected to widen beyond agency personnel to veterinarians, quarantine-station staff, certified applicators at livestock and game facilities, zoo and wildlife staff, rehabilitation centers, and other wildlife professionals. (fda.gov)