FDA expands screwworm emergency toolkit with topical spray EUA: full analysis

The FDA has added another emergency-use option to the growing New World screwworm response, authorizing F10 Antiseptic Wound Spray with Insecticide for prevention and treatment of myiasis in a wide range of species beyond cattle. Announced March 10, 2026, the EUA covers cattle, horses, minor hoofstock including sheep and goats, raptors and other wild birds, pet birds, and captive wild, exotic, and zoo mammals, but explicitly excludes domestic dogs and cats. (fda.gov)

The move fits into a broader federal effort that accelerated after HHS allowed FDA to use emergency authorities for animal drugs targeting New World screwworm, while USDA, CDC, and state agencies expanded surveillance and response planning. CDC said in January 2026 that outbreak-related animal cases had reached Tamaulipas, Mexico, bordering Texas, though no U.S. animal or human infestations tied to the outbreak had been identified as of January 20, 2026. USDA’s wider response has included movement controls, outreach, and sterile insect releases, with a new Texas dispersal center opening in February 2026 as part of a longer-term containment strategy. FDA has also been building out a broader emergency drug portfolio, including an OTC EUA for Ivomec (ivermectin) injectable solution to prevent NWS infestations in cattle when administered within 24 hours of birth, at castration, or when a wound appears. (fda.gov)

What changed here is species scope. FDA said F10 is the first product authorized for NWS indications in species beyond the cattle, dog, and cat products already conditionally approved or cleared under EUA. The spray is sold over the counter and was already indexed in the U.S. minor-species pathway, dating to 2015, for topical antiseptic use, fly repellency, and fly-strike treatment in raptors, pet birds, captive small mammals, captive reptiles, and captive exotic or zoo mammals. Under the NWS EUA, however, its use expands to additional at-risk species and to a specific emergency indication tied to screwworm. That broader scope now sits alongside cattle-focused emergency options such as Ivomec, which FDA said may be effective for prevention rather than treatment and remains limited to cattle under its EUA. (fda.gov)

FDA’s fact sheet adds important operational details for practice teams. The spray contains benzalkonium chloride, polyhexanide, and cypermethrin; directions call for wound cleaning first, 1 to 2 sprays per wound, a maximum of five applications per animal with multiple wounds, and repeat application once weekly if needed or as advised by a veterinarian. Because the product is water soluble, it should be reapplied after bathing or rain exposure. FDA also says to use disposable gloves, apply only in well-ventilated areas, and avoid use with soaps or other chemicals. For food-producing species, treated cattle, goats, and sheep have a 30-day slaughter withdrawal, and milk from treated cows, goats, and sheep must be discarded for 10 days. Horses treated under the EUA cannot be intended for human consumption. (fda.gov)

The evidence base is also worth noting. FDA said there is no direct evidence that F10 is effective against Cochliomyia hominivorax. Instead, the agency relied on data from its indexed use in fly-strike settings, evidence involving related blowfly species common in South Africa, and the known antiseptic and insecticidal properties of the formulation. In other words, the authorization reflects an emergency judgment that the product may be effective and that its potential benefits outweigh its risks, rather than the kind of species-specific efficacy package clinicians would expect from a standard approval. FDA used similar emergency reasoning for Ivomec in cattle, concluding that available evidence supported a reasonable belief that it may be effective for prevention of NWS myiasis in specific wound-risk settings, while pairing that access with use limitations and withdrawal instructions. (fda.gov)

Industry and regulatory reaction has framed the EUA as another practical tool rather than a standalone solution. Texas Agriculture Commissioner Sid Miller publicly welcomed the authorization the day after FDA’s announcement, underscoring the pressure on producers and animal health officials in high-risk regions. FDA has similarly positioned F10 as one piece of a broader NWS drug portfolio that now includes products for cattle, dogs, and cats, while noting that emergency and conditional pathways are being used to close urgent treatment and prevention gaps. In cattle, that portfolio now includes the OTC Ivomec injectable from Boehringer Ingelheim Animal Health USA, which FDA has previously approved for other parasites in cattle, swine, reindeer, and American bison. (texasagriculture.gov)

Why it matters: For veterinary professionals, this EUA is most significant because it reaches the species categories that often fall outside mainstream livestock and companion-animal drug development, including birds, exotics, wildlife, and zoo mammals. That gives clinicians, shelters, wildlife rehabilitators, zoological teams, and livestock practitioners a clearer legal framework for wound-based prevention and treatment in species that may be exposed through geography, travel, importation, or contact with affected areas. It also raises the importance of triage and communication: the product is not for dogs or cats, horses treated under the EUA cannot be intended for human consumption, and food-animal withdrawal and milk discard instructions are non-negotiable. For cattle producers, the parallel availability of OTC injectable ivermectin under EUA adds another prevention option, but also another compliance layer: Ivomec carries a 35-day slaughter withdrawal and cannot be used in female dairy cattle producing milk for human consumption or in calves intended for veal. For pet parents and animal caretakers, the OTC status may make access easier, but the species restrictions and wound-management details mean veterinary guidance still matters. Producers are also being urged to use antiparasitic drugs only when medically necessary and as part of a broader parasite-management strategy to help limit resistance pressure. (fda.gov)

What to watch: The next signals will be whether FDA adds more species-specific authorizations, whether field experience supports broader uptake of F10 in at-risk settings, and how quickly the larger federal containment campaign can suppress northward spread. If outbreak pressure increases, veterinarians should expect more guidance tied to surveillance, interstate and international animal movement, and emergency drug availability. The agency’s use of emergency authority for both topical and injectable OTC products suggests the toolbox may continue to expand as regulators try to cover different species, wound scenarios, and production settings. (fda.gov)