Zoetis Wins EUA for Simparica TRIO Against NWS in Dogs

The US Food and Drug Administration (FDA) has issued an Emergency Use Authorization (EUA) for Zoetis’ Simparica TRIO (sarolaner, moxidectin, pyrantel chewable tablets) for the treatment of New World screwworm (NWS) infestations, also known as myiasis, in dogs and puppies. Announced on 13 August 2026, the authorisation gives US veterinarians a new treatment option amid ongoing containment efforts to prevent NWS establishment beyond specific detected areas.

Simparica TRIO was originally approved by the FDA in 2020 for heartworm, flea and tick-related indications in dogs and puppies. Sarolaner, one of its three active ingredients, belongs to the isoxazoline class of antiparasitic drugs, which have been associated with neurologic adverse reactions including muscle tremors, loss of coordination and seizures. The drug is available only by prescription from a licensed veterinarian. The EUA authorises Simparica TRIO for treatment only, not prevention of NWS.

NWS is currently only detected in specific areas of Texas and New Mexico, according to the USDA’s Animal and Plant Health Inspection Service (APHIS), with additional risk associated with certain countries south of the US border. Timothy Schell, Ph.D., Director of the FDA’s Center for Veterinary Medicine, positioned the authorisation as ensuring US preparedness in the unlikely event of wider spread. The action extends Zoetis’ industry-leading Simparica TRIO franchise into an emergency use category and reinforces the company’s dominance in the US companion animal parasite prevention market. The EUA remains effective until revoked or until the HHS Secretary terminates the underlying August 2025 emergency declaration.

The commercial signal is a rapidly maturing companion animal parasitology category where regulatory pathways for zoonotic and emerging disease treatment are becoming meaningful commercial differentiators. Zoetis’ EUA success extends its dominant Simparica TRIO franchise position. Expect Boehringer Ingelheim (NexGard Combo), Elanco (Credelio Plus), MSD Animal Health (Bravecto) and Merial to sharpen their own preparedness product positioning through the rest of 2026 and 2027.

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