FDA Issues Emergency Use Authorization for Drug to Treat New World Screwworm in Dogs and Puppies
Silver Spring, MD, Aug. 13, 2026 (GLOBE NEWSWIRE) — The U.S. Food and Drug Administration today issued an Emergency Use Authorization (EUA) for Simparica TRIO (sarolaner, moxidectin, and pyrantel chewable tablets) for the treatment of New World screwworm (NWS) infestations (myiasis) in dogs and puppies.
Currently, most dogs in the U.S. are at low risk of NWS exposure due to their geographic location. However, dogs that live in, travel to, or return from areas where NWS infestations have been identified by state or federal animal health officials, as well as certain countries south of the U.S. border, should be closely monitored for signs of infestation, such as visible maggots or foul odors in wounds or body openings (eyes, ears, nose, mouth). Seek immediate veterinary care for infested dogs.
For up-to-date U.S. case information, see the U.S. Department of Agriculture’s dashboard of Confirmed Detections of New World Screwworm. At present, NWS has only been detected in specific areas of Texas and New Mexico.
“The FDA continues to authorize products to give veterinarians and pet owners multiple treatment options, in the unlikely event animals under their care become infested with New World screwworm,” said Acting FDA Commissioner Kyle Diamantas, J.D. “To date, the U.S. has been successful in containing the spread of NWS. We are hopeful it will remain that way, and by authorizing products like this, the U.S. will be ready if the need arises.”
Based on the totality of the scientific evidence available, the FDA has concluded it is reasonable to believe that Simparica TRIO may be effective in the treatment of NWS myiasis in dogs and puppies when used as authorized, and the known and potential benefits of the product outweigh its known and potential risks. Simparica TRIO is not authorized for the prevention of NWS.
“We want dog owners to be informed, not alarmed,” said Timothy Schell, Ph.D., director of the FDA’s Center for Veterinary Medicine. “The best thing dog owners can do right now is stay aware of the situation, know the signs of infestation, and have a conversation with their veterinarian if they have concerns.”
Simparica TRIO was approved by the FDA in 2020 for heartworm, flea, and tick-related indications in dogs and puppies. Sarolaner, one of the active ingredients in Simparica TRIO, belongs to a class of antiparasitic drugs called isoxazolines. Although isoxazoline products are commonly used and safe for most dogs, the products have been associated with neurologic adverse reactions, including muscle tremors, loss of coordination, and seizures. Because professional expertise is required to monitor for and respond to these reactions, Simparica TRIO is available only by prescription from a licensed veterinarian. Dog owners should consult with a veterinarian to determine if Simparica TRIO is appropriate for their dog.
Detailed product information can be found in the Fact Sheet for Veterinarians: Emergency Use Authorization of Simparica TRIO (sarolaner, moxidectin, and pyrantel chewable tablets) for New World Screwworm (NWS).
This EUA will be effective until it is revoked or the HHS Secretary terminates the declaration that the potential public health emergency presented by NWS justifies the emergency use authorization of animal drugs for NWS.
Simparica TRIO is sponsored by Zoetis Inc., based in Kalamazoo, Michigan.
Related Information
Freedom of Information Summary: Simparica TRIO (EUA 006691)Letter of Authorization: Simparica TRIO (EUA 006691)Fact Sheet for Veterinarians: Emergency Use Authorization of Simparica TRIO (sarolaner, moxidectin, and pyrantel chewable tablets) for New World Screwworm (NWS)Fact Sheet for Pet Owners and Veterinarians about Potential Adverse Events Associated with Isoxazoline Flea and Tick ProductsAnimal Drugs for New World ScrewwormEmergency Use Authorization of Animal Drugs for NWSScrewworm.gov – Unified Government Response to Protect the United States
Media: FDA Request for Comment
Consumer: 888-INFO-FDA
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The FDA, an agency within the U.S. Department of Health and Human Services, protects the public health by assuring the safety, effectiveness, and security of human and veterinary drugs, vaccines and other biological products for human use, and medical devices. The agency also is responsible for the safety and security of our nation’s food supply, cosmetics, dietary supplements, radiation-emitting electronic products, and for regulating tobacco products.
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