FDA authorizes fluralaner for emergency treatment of New World screwworm in dogs

The FDA has issued an emergency use authorization (EUA) for fluralaner chewable tablets (Bravecto; Merck Animal Health) to treat New World screwworm (NWS) infestations (myiasis) in dogs and puppies. The authorization adds another prescription option to the set of NWS treatments now available to veterinarians.¹

The agency issued the November 3 authorization to Intervet Inc.¹ After weighing the totality of the available scientific evidence, the FDA concluded it is reasonable to believe Bravecto may be effective against NWS myiasis in dogs and puppies when used as authorized. The agency also determined that the product’s known and potential benefits outweigh its known and potential risks.¹

Bravecto already holds FDA approval for various flea and tick indications in dogs and puppies.¹

Which dogs are at risk

The FDA considers most dogs in the US to be at low risk of NWS exposure because confirmed cases are in a limited geographic region.¹ The agency advises close monitoring for dogs that live in, travel to, or return from areas where state or federal animal health officials have identified NWS infestations. The same advice applies to dogs in, traveling to, or returning from certain countries south of the US border.¹

Signs of infestation include visible maggots or foul odors in wounds or body openings such as the eyes, ears, nose, and mouth. The FDA directs owners of infested dogs to seek veterinary care immediately.¹

The parasite’s return to the US was confirmed in June, when the USDA’s Animal and Plant Health Inspection Service confirmed NWS in a bovine in Zavala County, Texas. Days later, USDA confirmed a case in a dog living in Lea County, New Mexico. For current US case information, the FDA points to the USDA’s Confirmed Detections of New World Screwworm dashboard.¹

Related: See our full New World screwworm coverage.

Prescription only, with a safety caveat

Fluralaner belongs to the isoxazoline class of antiparasitic drugs. According to the FDA, isoxazolines are commonly used and safe for most dogs. However, the class has been associated with neurologic adverse reactions, including muscle tremors, loss of coordination, and seizures.¹

Because monitoring for and responding to the neurologic reactions requires professional expertise, Bravecto is available only by prescription from a licensed veterinarian.¹ The FDA’s announcement links to a fact sheet for veterinarians on the Bravecto EUA. It also links to the agency’s fact sheet on potential adverse events associated with isoxazoline flea and tick products.¹

A growing list of options for dogs

The Bravecto EUA will stay in effect until the FDA revokes it or the HHS secretary ends the declaration that the potential public health emergency presented by NWS justifies emergency use authorization of animal drugs.¹ HHS issued the NWS emergency declaration in August 2025, allowing the FDA to temporarily authorize certain animal drugs approved for other conditions to be used against NWS.

Several other products for dogs have been authorized or conditionally approved since the declaration. Lotilaner (Credelio; Elanco Animal Health) became the first product authorized to treat NWS in dogs in October 2025. The FDA conditionally approved lotilaner, moxidectin, praziquantel, and pyrantel chewable tablets (Credelio Quattro-CA1) to treat NWS in dogs and puppies in December 2025.² An EUA for afoxolaner chewable tablets (NexGard) followed in February 2026.³

In June 2026, the FDA authorized generic nitenpyram tablets as an over-the-counter treatment for NWS in dogs and cats, the first generic animal drug authorized against the parasite.⁴ In August 2026, the agency authorized sarolaner, moxidectin, and pyrantel chewable tablets (Simparica Trio; Zoetis) for treatment of NWS myiasis in dogs and puppies. The following month, the FDA authorized nitenpyram tablets (Capstar) and revised the generic nitenpyram authorization to cover both prevention and treatment. With the September authorizations, the two nitenpyram products became the first emergency-authorized NWS prevention options for dogs and cats.

References

1. FDA issues emergency use authorization for drug to treat New World screwworm infestations in dogs and puppies. News release. FDA. November 3, 2026. Accessed November 3, 2026. https://www.fda.gov/animal-veterinary/cvm-updates/fda-issues-emergency-use-authorization-drug-treat-new-world-screwworm-infestations-dogs-and-puppies
2. FDA conditionally approves drug to treat New World screwworm in dogs. News release. FDA. December 17, 2025. Accessed November 3, 2026. https://www.fda.gov/animal-veterinary/cvm-updates/fda-conditionally-approves-drug-treat-new-world-screwworm-dogs
3. FDA issues emergency use authorizations for drugs to treat New World screwworm in dogs and cats. News release. FDA. February 18, 2026. Accessed November 3, 2026. https://www.fda.gov/animal-veterinary/cvm-updates/fda-issues-emergency-use-authorizations-drugs-treat-new-world-screwworm-dogs-and-cats
4. FDA issues emergency use authorization for generic over-the-counter drug to treat New World screwworm in dogs and cats. News release. FDA. June 11, 2026. Accessed November 3, 2026. https://www.fda.gov/news-events/press-announcements/fda-issues-emergency-use-authorization-generic-over-counter-drug-treat-new-world-screwworm-dogs-and