FDA Authorizes First-Ever Emergency Use Drug for Canine Screwworm Infestations

The U.S. Food and Drug Administration has issued an Emergency Use Authorization (EUA) for Credelio (lotilaner) chewable tablets, marking the first time the agency has granted such authorization for an animal drug. According to the FDA, the decision was made because available scientific evidence indicates that Credelio may be effective in treating New World screwworm (NWS) infestations in dogs and puppies, and that its potential benefits outweigh the known and potential risks. This action comes as New World screwworm, a parasite that infests warm-blooded animals, has been progressing northward since 2022, posing an emerging threat to livestock, food security, and animal health.

While most dogs in the United States are at a low risk of exposure to NWS, those residing near the U.S.-Mexico border or those that have recently traveled to countries with active NWS cases are at a higher risk of encountering the parasite. The FDA emphasizes that the risk to human health from NWS in the U.S. remains very low. The parasite, once eradicated from North America and Central America, can cause severe tissue damage and, in some instances, death in infected animals. The HHS Secretary determined in August 2025 that NWS presents a significant potential for a public health emergency, empowering the FDA to issue EUAs for animal drugs to combat the threat. This specific authorization for Credelio will remain in effect until it is revoked or the HHS Secretary ends the public health emergency declaration.

Credelio, which contains the active ingredient lotilaner, belongs to the isoxazoline class of antiparasitic drugs. The FDA previously approved Credelio in 2018 for indications related to flea and tick prevention in dogs and puppies. Although isoxazoline products are generally considered safe and are widely used for most dogs, there have been reports of neurological adverse reactions associated with these drugs, including symptoms such as muscle tremors, ataxia, and seizures. The FDA advises pet owners to consult with a veterinarian to determine if Credelio is a suitable treatment option for their pet.

Due to the necessity for professional oversight to monitor for and address potential adverse reactions, Credelio is available only by prescription from a licensed veterinarian. The FDA has made detailed product information available for veterinary practitioners through a Fact Sheet for Veterinarians concerning the Emergency Use Authorization of Credelio. The drug is sponsored by Elanco US Inc., headquartered in Indianapolis, Indiana.

Article by Mel Anara, based upon information from the U.S. Food and Drug Administration

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