FDA grants emergency approval for Simparica Trio to combat New World screwworm infestations in dogs
The FDA has issued an emergency use authorization for Simparica Trio to treat New World screwworm myiasis in dogs and puppies, providing veterinarians with another option for affected animals. The chewable tablet, which combines sarolaner, moxidectin, and pyrantel, is already approved for other parasitic conditions but is now authorized specifically for screwworm treatment. The FDA emphasizes that while the risk remains low, awareness and vigilance are key.
The US Food and Drug Administration (FDA) has granted an emergency use authorization (EUA) for Simparica Trio, a chewable tablet containing sarolaner, moxidectin, and pyrantel, to treat New World screwworm (NWS) myiasis in dogs and puppies. This authorization comes as part of ongoing efforts to address the rare but serious infestations caused by the larvae of the NWS fly (*Cochliomyia hominivorax*), which feed on living tissue in open wounds or mucous membranes. ## Understanding the threat and treatment The FDA's decision follows a review of available scientific evidence, concluding that Simparica Trio may be effective in treating NWS infestations in eligible dogs and puppies, with benefits outweighing potential risks. The EUA is limited to treatment only and does not cover prevention. The product will be available by prescription from licensed veterinarians while the EUA remains active. Timothy Schell, PhD, director of the FDA's Center for Veterinary Medicine, noted that while most US dogs face a low risk of exposure-with confirmed cases limited to parts of Texas and New Mexico-owners should stay informed. "Knowing the signs of infestation and discussing concerns with a veterinarian is crucial," he advised. Symptoms include visible maggots or a foul odor from wounds or body openings. ## Expanding treatment options This EUA adds to the FDA's growing list of NWS-related authorizations since the parasite's detection in the US. Simparica Trio, already approved for preventing heartworm disease and treating fleas, ticks, roundworms, and hookworms, now offers veterinarians a labeled option for dogs and puppies already on the medication for other parasites. The product combines three active ingredients: sarolaner (an isoxazoline-class parasiticide), moxidectin, and pyrantel. However, veterinarians should remain cautious, as isoxazoline products have been linked to neurological side effects, including tremors, ataxia, and seizures, even in dogs without prior seizure history. A thorough medical review is recommended before prescribing. ## Preparedness and vigilance Kyle Diamantas, JD, acting FDA commissioner, reiterated the agency's commitment to providing multiple treatment options. "While the US has successfully contained NWS spread so far, authorizing products like Simparica Trio ensures readiness if needed," he said. Veterinarians in affected regions or treating dogs that have traveled near the US-Mexico border are urged to maintain vigilance and report suspected cases through proper channels.
