The U.S. Food and Drug Administration (FDA) has issued an Emergency Use Authorization (EUA) for F10 Antiseptic Wound Spray with Insecticide to help prevent and treat New World screwworm (Cochliomyia hominivorax)infestations in animals.
The authorization took effect March 10, 2026. As a result, veterinarians and producers now have another tool to help manage this serious parasitic threat.
New World screwworm infestations, known as myiasis, occur when fly larvae invade open wounds and feed on living tissue. If left untreated, the larvae can quickly damage healthy tissue. Therefore, early treatment plays a critical role in protecting animal welfare and limiting losses.
Emergency Authorization Supports Animal Health
To address this risk, the FDA reviewed available scientific evidence before granting the emergency authorization. Based on that review, the agency determined that the product may help prevent and treat screwworm infestations during the current emergency declaration.
Importantly, F10 Antiseptic Wound Spray already appears in the FDA’s Minor Species Index. It is commonly used as a topical antiseptic and fly-strike treatment in several minor species.
However, the emergency authorization expands its potential use temporarily. Specifically, it allows the product to be used in cattle, horses, and several minor hoofstock species, as well as certain birds and captive exotic mammals.
At the same time, federal officials stress that the authorization remains temporary. In other words, the product is not fully approved for this specific use outside the emergency authorization.
Important Use Restrictions for Livestock Producers
Because the product falls under an emergency authorization, producers must follow the directions and safety restrictions carefully.
For example:
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Cattle, goats, and sheep cannot be slaughtered for human consumption within 30 days of treatment.
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Milk from treated animals cannot enter the food supply during treatment or for 10 days afterward.
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The product cannot be used in dogs or cats.
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It cannot be used in horses intended for human consumption.
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In addition, treated calves—or calves born to treated cows—cannot be processed for veal, because no withdrawal period has been established.
When applying the product, producers should spray it directly onto wounds. To ensure full coverage, they should hold the bottle four to eight inches away from the wound site.
If necessary, treatment can be repeated weekly. However, producers should always follow veterinary guidance.
Monitoring Treatment Effectiveness
The spray contains cypermethrin, an insecticide known to control several fly species associated with myiasis.
However, researchers currently have limited direct evidence showing its effectiveness specifically against New World screwworm. Even so, scientists note that screwworm flies belong to the same family as other blowflies studied in previous trials.
Because these flies share similar life cycles and characteristics, regulators concluded that the product may still provide useful control.
Nevertheless, producers should monitor wounds closely. If a wound worsens or fails to heal, veterinary advice is recommended.
Meanwhile, scientists also warn that insects can develop resistance to pyrethroid insecticides such as cypermethrin. For that reason, careful monitoring remains important.
Veterinary Guidance Remains Important
Veterinarians continue to play a central role in managing screwworm infestations. They can help diagnose cases early and recommend appropriate treatment options.
In addition, veterinarians can advise producers if animals experience a reaction to the product. Possible side effects include hives, itching, or hair loss.
Full Fact Sheet Available
Because the emergency authorization includes detailed safety information, withdrawal periods, and reporting procedures, the FDA has published a full fact sheet.
Producers and veterinarians can review the complete document here.
