FDA Authorizes Fluralaner Chewables for New World Screwworm in Dogs

On November 3, the FDA issued an emergency use authorization (EUA) for fluralaner chewable tablets (Bravecto; Merck Animal Health, manufactured by Intervet Inc.) to treat New World screwworm (NWS) infestations — myiasis — in dogs and puppies. The authorization adds a prescription option to a treatment arsenal that has expanded almost monthly since HHS declared an NWS emergency in August 2025.

The FDA reached its decision after weighing the totality of the available scientific evidence, concluding it is reasonable to believe fluralaner chewable tablets 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. Bravecto already holds FDA approval for various flea and tick indications in dogs and puppies.

What changes at the exam table?

For companion-animal practitioners, the EUA means one more prescription tool for infested dogs. The FDA considers most dogs in the US to be at low risk of NWS exposure, because confirmed cases sit in a limited geographic region. 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, and the same advice applies to dogs moving to or from certain countries south of the US border.

Clinicians should watch for visible maggots or foul odors in wounds or body openings such as the eyes, ears, nose, and mouth. Owners of infested dogs should seek veterinary care immediately.

The parasite's return to the US was confirmed in June, when the USDA Animal and Plant Health Inspection Service confirmed NWS in a bovine in Zavala County, Texas. Days later, the USDA confirmed a case in a dog living in Lea County, New Mexico. For current case information, the FDA points veterinarians to the USDA's Confirmed Detections of New World Screwworm dashboard. That bovine case underscores the food-animal dimension of the outbreak, even though this authorization covers dogs only.

Why prescription-only status matters

Fluralaner belongs to the isoxazoline class of antiparasitic drugs. According to the FDA, isoxazolines are commonly used and safe for most dogs, but the class has been associated with neurologic adverse reactions, including muscle tremors, loss of coordination, and seizures. Because monitoring for and responding to those neurologic reactions requires professional expertise, fluralaner remains available only by prescription from a licensed veterinarian. The FDA's announcement links to a fact sheet for veterinarians on the drug's EUA and to a fact sheet on potential adverse events associated with isoxazoline flea and tick products.

How the NWS treatment arsenal has grown

The EUA remains in effect until the FDA revokes it or the HHS secretary ends the declaration that the potential public health emergency posed by NWS justifies emergency authorization of animal drugs. Since that August 2025 declaration, the agency has moved quickly:

• October 2025: Lotilaner (Credelio; Elanco Animal Health) became the first product authorized to treat NWS in dogs.
• December 2025: The FDA conditionally approved lotilaner, moxidectin, praziquantel, and pyrantel chewable tablets (Credelio Quattro-CA1) for NWS in dogs and puppies.
• February 2026: An EUA followed for afoxolaner chewable tablets (NexGard).
• June 2026: The FDA authorized generic nitenpyram tablets as an over-the-counter NWS treatment for dogs and cats — the first generic animal drug authorized against the parasite.
• August 2026: The agency authorized sarolaner, moxidectin, and pyrantel chewable tablets (Simparica Trio; Zoetis) for NWS myiasis in dogs and puppies.
• September 2026: The FDA authorized nitenpyram tablets (Capstar) and revised the generic nitenpyram authorization to cover both prevention and treatment, making the two nitenpyram products the first emergency-authorized NWS prevention options for dogs and cats.

Fluralaner now becomes the seventh product to gain an emergency or conditional NWS authorization in roughly fourteen months. Whether the EUA pathway continues to widen — or converts toward full approvals — will depend on how far north the parasite travels and how the USDA's detection map evolves.