The U.S. Food and Drug Administration has issued an Emergency Use Authorization for Simparica TRIO to treat New World screwworm infestations in dogs and puppies, giving veterinarians another treatment option if the parasitic infestation spreads to more animals in the United States.

The authorization covers Simparica TRIO, a chewable tablet containing sarolaner, moxidectin and pyrantel, a news release said. The FDA said the product may be effective in treating New World screwworm, or NWS, myiasis when used according to the authorization. The agency determined that the known and potential benefits outweigh the known and potential risks.

The drug is not authorized to prevent New World screwworm infestations.

Most dogs in the United States currently face a low risk of exposure because of where they live. However, dogs that live in, travel to or return from areas where state or federal animal health officials have identified NWS infestations, as well as certain countries south of the U.S. border, should be closely monitored.

Signs of an infestation can include visible maggots or foul odors coming from wounds or body openings, including the eyes, ears, nose and mouth. Dogs suspected of being infested should receive immediate veterinary care.

The U.S. Department of Agriculture maintains a dashboard with up-to-date information on confirmed New World screwworm detections. At present, NWS has been detected only 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. in the release. “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.”

The FDA's Center for Veterinary Medicine also urged dog owners to remain alert without becoming alarmed.

“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.”

The FDA originally approved Simparica TRIO in 2020 for heartworm, flea and tick-related indications in dogs and puppies. Sarolaner, one of the drug's active ingredients, belongs to a class of antiparasitic medications known as isoxazolines.

While isoxazoline products are commonly used and considered safe for most dogs, they have been associated with neurological adverse reactions, including muscle tremors, loss of coordination and seizures. Because professional expertise is needed to monitor and respond to those reactions, Simparica TRIO is available only by prescription from a licensed veterinarian.

Dog owners should consult a veterinarian to determine whether Simparica TRIO is appropriate for their dog.

The FDA has provided detailed information in the Fact Sheet for Veterinarians: Emergency Use Authorization of Simparica TRIO (sarolaner, moxidectin, and pyrantel chewable tablets) for New World Screwworm (NWS).

The emergency authorization will remain in effect until the FDA revokes it or the HHS secretary terminates the declaration that the potential public health emergency posed by NWS justifies the emergency use authorization of animal drugs for the disease.

Simparica TRIO is sponsored by Zoetis Inc., which is based in Kalamazoo, Michigan.