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

CURRENT FULL VERSION: The FDA has issued an Emergency Use Authorization for F10 Antiseptic Wound Spray with Insecticide, giving veterinarians and animal caretakers a new over-the-counter option to prevent and treat New World screwworm myiasis across a notably broad set of species. Under the EUA, the spray can be used in cattle, horses, minor species of hoof stock, raptors and other wild birds, pet birds, and captive wild, exotic, and zoo mammals. The authorization, dated March 10, 2026, does not include domestic dogs or cats. (fda.gov)

The move fits into a larger federal effort that accelerated after HHS issued an emergency declaration on August 19, 2025, allowing FDA to authorize animal drugs for New World screwworm prevention and treatment. Since then, FDA has added multiple pathways for different species and use cases, including conditional approval of Dectomax-CA1 for cattle in September 2025 and an EUA for the over-the-counter injectable Ivomec (ivermectin) in cattle in February 2026. FDA said it was reasonable to believe Ivomec may be effective for preventing New World screwworm infestations in cattle when administered within 24 hours of birth, at the time of castration, or when a wound appears. That authorization also underscored how product-specific these emergency pathways are: Ivomec is not for use in female dairy cattle producing milk for human consumption or in calves that will be processed for veal, and it carries a 35-day slaughter withdrawal. At the same time, USDA has been expanding sterile-fly infrastructure, including a dispersal center in Texas that opened in February 2026, as officials try to keep the parasite from moving north. (fda.gov)

F10 is not a brand-new product, but this is a meaningful change in how it can be used. FDA added it to the Index of Legally Marketed Unapproved New Animal Drugs for Minor Species in 2015 as a topical antiseptic for surface wounds, fly repellency, and fly-strike treatment in certain minor species. In the EUA summary, FDA said the dosage regimen does not change from the previously indexed product, and concluded the product may be effective against New World screwworm because its insecticidal component, cypermethrin, may help prevent and treat larval infestation when applied to wounds or sites of myiasis, while the antiseptic components may help reduce secondary infection risk. (fda.gov)

The authorization also comes with detailed use limitations that veterinary teams will need to communicate clearly. Cattle, goats, and sheep treated with the spray must not be slaughtered for human consumption within 30 days, and milk from cows, goats, or sheep during treatment and for 10 days afterward cannot enter the human food supply. A withdrawal period has not been established for pre-ruminating calves, so treated calves, and calves born to treated cows, must not be processed for veal. The product also must not be used in horses intended for human consumption, in domestic dogs or cats, or in food-producing species that have not been assigned a withdrawal period. FDA also notes that extralabel use is not permitted for this EUA product. (fda.gov)

Public expert commentary on the F10 authorization itself appears limited so far, but industry messaging around other recent screwworm authorizations has emphasized preparedness and speed. In Boehringer Ingelheim’s announcement of the Ivomec EUA, a company executive described the authorization as an important preventive tool for cattle producers and veterinarians. That framing is consistent with FDA’s broader position that no single product will solve screwworm risk, and that emergency authorizations are intended to fill gaps where adequate approved alternatives are not available. The Ivomec coverage also added another practical point likely to matter as more products enter emergency use: because it is available over the counter, producers are responsible for following the labeling and fact sheet, and FDA-linked messaging has encouraged antiparasitic drugs to be used only when medically necessary and as part of a comprehensive parasite-management strategy to help reduce resistance pressure and preserve effectiveness. (biospace.com)

Why it matters: For veterinary professionals, the significance here is less about one spray and more about species coverage. Cattle-focused tools have been emerging first, but F10 expands options for equine, avian, exotic, zoo, and some hoof-stock patients, where clinicians may face wound-management and parasite-control decisions with fewer labeled products. Because New World screwworm larvae can cause rapid, severe tissue damage, access to a topical product that may be used both preventively on wounds and therapeutically on infestations could be especially relevant for practices in border states, referral centers, wildlife rehabilitation, zoological medicine, and any setting managing transported or outdoor animals. (fda.gov)

The practical challenge is compliance. This EUA is tightly bounded by species, food-animal residue rules, and use directions, and it sits alongside a growing but fragmented list of screwworm-related products with different statuses: full approval, conditional approval, indexing, and EUA. That means veterinary teams may need to spend more time verifying exactly which product can be used in which species, under what circumstances, and with what withdrawal intervals. For example, F10 is a topical OTC option spanning multiple species but with a 30-day slaughter withdrawal in cattle, goats, and sheep and a 10-day milk discard period, while Ivomec’s cattle-only EUA is preventive rather than therapeutic and carries a 35-day slaughter withdrawal plus dairy and veal restrictions. For mixed practices, that’s likely to become a recurring workflow issue if additional screwworm products reach the market under emergency mechanisms. Stewardship is part of that picture too, especially as federal messaging around ivermectin has stressed using antiparasitics only when medically necessary and within a broader parasite-control plan. (fda.gov)

What to watch: The next phase will likely include more FDA authorizations, more USDA operational updates, and possibly additional guidance for veterinarians as federal agencies continue building a layered response that combines drug access, surveillance, import controls, and sterile-insect release. If New World screwworm pressure near the U.S. border persists, expect veterinary preparedness messaging to become more specific by region and species, with continued emphasis on product-specific directions, withdrawal intervals, and resistance-conscious use. (fda.gov)