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Federal regulators have issued an Emergency Use Authorization for Simparica TRIO to treat New World screwworm infestations in dogs, according to announcements from the U.S. Food and Drug Administration. Acting FDA Commissioner Kyle Diamantas stated that the parasite remains contained within the United States, framing the August 13, 2026, action as a proactive measure to ensure veterinarians and pet owners have multiple options in the unlikely event an animal becomes infested.
Oral Chewable Authorized Strictly for Treatment
Simparica TRIO is an oral chewable tablet combining sarolaner, moxidectin, and pyrantel. According to the FDA, the product is authorized strictly for the treatment of New World screwworm infestations in dogs and puppies, rather than for prevention. The medication is available exclusively by prescription from a licensed veterinarian. Timothy Schell, director of the FDA’s Center for Veterinary Medicine, emphasized that the regulatory action aims to inform dog owners rather than cause alarm.
Broad Federal Response Spanning Livestock and Pets
This companion animal authorization follows earlier federal regulatory steps aimed at livestock and broader animal health sectors. On August 7, 2026, the FDA cleared CLiK Extra as a preventive wound spray for sheep, cattle, goats, and swine. Unlike that topical livestock preventive applied by producers or veterinarians in pens, Simparica TRIO is an oral chewable administered at home to household pets.
Additionally, the FDA previously granted conditional approval on December 17, 2025, to Credelio Quattro-CA1 chewable tablets for treating screwworm larvae in dogs. That prior authorization utilized a priority zoonotic animal drug designation under the Coronavirus Aid, Relief, and Economic Security (CARES) Act, giving Elanco US Inc. up to five years to generate full effectiveness data.
Geographic Exposure Risks and Active Tracking
The FDA notes that most dogs in the United States face a low risk of exposure based on geography. However, the agency advises close monitoring for dogs that live in, travel to, or return from areas where infestations have been identified by state or federal animal health officials, including specific regions of Texas and New Mexico, as well as countries south of the U.S. border.
The detection picture has shifted in recent months. Department of Agriculture counted 45 confirmed U.S. detections and five active cases during that reporting window. The FDA currently directs households to check the USDA tracking dashboard for real-time confirmation counts.
Recognizing Symptoms and Securing Care
New World screwworm flies lay eggs in and on open wounds and mucous membranes, allowing larvae to burrow into living tissue. The FDA advises owners to watch for visible maggots or a foul odor in wounds, eyes, ears, nose, or mouth. Because minor injuries like scratches, tick bites, surgical sites, or newborn navels can attract the flies, post-injury inspections are recommended in affected regions. Infested animals require immediate professional veterinary care.
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