FDA Approves Screwworm Drug for Dogs | Emergency Use Authorization

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FDA Authorizes First Drug to Combat Resurgent New World Screwworm in Dogs

The U.S. Food and Drug Administration issued an Emergency Use Authorization (EUA) on October 24, 2025, for Credelio (lotilaner) chewable tablets, marking a critical step in addressing the growing threat of New World screwworm (NWS) to companion animals. This is the first time the FDA has authorized an animal drug via EUA and the first approval specifically for treating NWS in dogs and puppies.

The FDA’s swift action underscores the seriousness of the situation. “The FDA acted swiftly to make a screwworm treatment available to American dog owners,” stated FDA Commissioner Marty Makary, M.D., M.P.H. “When it comes to emerging animal health threats, we need to be proactive, not reactive.”

Did you know? – New World screwworm was eradicated from North America and Central America, but cases began resurfacing in 2022. The parasite can cause severe tissue damage and death in animals.

A Resurgent Parasite

NWS,a parasitic fly larvae infestation,was previously eradicated from North america and Central America.However, since 2022, the parasite has been making a concerning comeback, posing a threat to livestock, food security, and potentially national security. The parasite infests warm-blooded animals – including livestock, pets, and wildlife – causing severe tissue damage and, in some cases, death.

The Secretary of Health and Human Services declared in august 2025 that NWS presented a notable potential public health emergency, enabling the FDA to expedite the EUA process for animal drugs targeting the parasite. While the risk to human health in the United States remains low, officials are prioritizing preventative measures.

Pro tip: Credelio was initially approved in 2018 for flea and tick control. Its active ingredient, lotilaner, is now being used to combat the New World screwworm.

Credelio: A Familiar Drug for a New Threat

Credelio, manufactured by Elanco US Inc., was originally approved in 2018 for flea and tick control in dogs and puppies. The active ingredient, lotilaner, belongs to the isoxazoline class of antiparasitic drugs. While generally safe, isoxazoline products have been linked to potential neurologic adverse reactions in some dogs, including muscle tremors, ataxia, and seizures.

“Pet owners should consult with a veterinarian to determine weather Credelio is appropriate for their pet,” officials emphasized. The drug will be available only through prescription, ensuring veterinary oversight to monitor for and manage any potential adverse reactions. Detailed facts for veterinary practitioners is available in the Fact Sheet for Veterinarians: Emergency Use Authorization of Credelio (lotilaner).

Reader question: Is the New world screwworm a threat to humans? Currently, the risk to human health in the U.S. is low, but preventative measures are being prioritized.

Geographic Risk and future Preparations

The majority of dogs in the U.S. face a low risk of NWS exposure due to their location. However, dogs residing near the U.S.-Mexico border, or those who have recently traveled to countries with active NWS cases, are considered more vulnerable.

The FDA is actively working to authorize additional drugs to combat NWS, extending beyond companion animals to include treatments for livestock and wildlife. “We are working expeditiously to authorize additional NWS drugs in the coming months for animals that could be affected by NWS,” explained Timothy Schell, Ph.D., director of the FDA’s Center for Veterinary Medicine.

This EUA for Credelio represents a crucial first step in bolstering the nation’s preparedness against this emerging animal health threat,demonstrating the FDA’s commitment to proactive solutions in the face of evolving challenges.

The FDA,