Elanco's Credelio™ (lotilaner) Receives First Ever FDA Emergency Use Authorization (EUA) against New World Screwworm (NWS) in Dogs

Rhea-AI Summary

Elanco (NYSE: ELAN) received an FDA Emergency Use Authorization (EUA) on October 24, 2025 for Credelio (lotilaner) to treat New World screwworm (NWS) infestations in dogs — the first-ever EUA for NWS in dogs. The EUA follows a peer-reviewed study reporting 100% efficacy against C. hominivorax larvae within 24 hours after oral dosing at the minimum recommended level in 11 naturally infested dogs. The authorization provides a ready treatment option for veterinarians and owners as confirmed NWS cases sit under 70 miles south of the U.S.-Mexico border. Limitations include small sample size, lack of a control group, and uncertain inferential value to U.S. populations.

Positive

• FDA EUA granted for Credelio to treat NWS in dogs
• Peer-reviewed study reported 100% efficacy within 24 hours
• Provides a ready-now treatment option for veterinarians and pet owners

Negative

• Efficacy evidence from only 11 naturally infested dogs
• Study lacked a control group and included mechanical removal, confounding effect
• Inferential value to U.S. dog populations is unknown

Insights

Veterinary pharmaceutical strategist

FDA issued the first-ever EUA for Credelio to treat New World screwworm in dogs, offering an immediate authorized treatment option.

Credelio gains a practical, near-term role: veterinarians and pet owners may use an already-approved oral parasiticide under an Oct. 24, 2025 EUA to treat New World screwworm (NWS) in dogs. A published study reported 100% efficacy within 24 hours at the labeled dose in naturally infested dogs, and the EUA establishes an official pathway to deploy that treatment should the fly enter the U.S.

The evidence supporting the EUA contains clear limitations that constrain extrapolation. The efficacy data derive from a small cohort (eleven dogs) in Brazil, lack a control group, and involve concurrent mechanical removal, which complicates attribution of the full treatment effect. Those constraints increase uncertainty about how consistently the result will replicate across broader U.S. cases and different clinical settings.

Key dependencies and near-term observables: confirmation of any U.S. NWS detection within the next weeks–months will determine actual EUA utilization; veterinarians’ uptake will hinge on guidance from federal agencies and field protocols; and additional controlled data or larger real-world case series would materially strengthen confidence. Watch for official APHIS or FDA procedural guidance and any post-EUA surveillance reports over the next 3–12 months.

EUA to Treat Dogs for NWS Issued Prior to Fly Being Detected in the U.S.; Action Prepares Veterinarians and Pet Owners with Treatment Options

• First FDA emergency use authorization (EUA) ever granted for NWS in dogs
• Action reinforces agency's commitment to providing treatment options for NWS in advance of the fly being detected in the U.S.
• Published literature showed Credelio may be effective in treating NWS in dogsⁱ
• Preventing open wounds through effective flea and tick control is critical in protecting pets from NWS

INDIANAPOLIS, Oct. 24, 2025 /PRNewswire/ -- Elanco Animal Health Incorporated (NYSE: ELAN) today announced it has received Emergency Use Authorization (EUA) from the U.S. Food and Drug Administration (FDA) for Credelio^™ (lotilaner) to treat New World screwworm (NWS) infestations in dogs. This is the first EUA ever granted by the Agency for NWS in dogs. Confirmed cases of NWS have been detected less than 70 miles south of the U.S.-Mexico border.ⁱⁱ This Emergency Use Authorization allows veterinarians and pet owners to have a ready-now treatment option if the fly enters the U.S.

"We appreciate the FDA's review of the scientific data demonstrating that Credelio may be an effective treatment against New World screwworm in dogs," said Dr. Ellen de Brabander, Executive Vice President of Innovation and Regulatory Affairs at Elanco. "This first ever Emergency Use Authorization for NWS in dogs gives veterinarians and pet owners peace of mind, knowing there's an authorized treatment option available as soon as they may need it."

The Emergency Use Authorization was based on a study evaluating the efficacy of Credelio against NWS. In the peer-reviewed study, published in Parasites & Vectors, oral administration of Credelio at the minimum recommended dosage demonstrated 100% efficacy against C. hominivorax larvae (NWS) within 24 hours of treatment in naturally infested dogs.ⁱ

There are limitations of the data supporting the benefits of Credelio for the treatment of infestations caused by NWS larvae. The study was conducted in a limited population of eleven naturally infested dogs in Brazil, and the inferential value to the United States population is unknown. The primary mechanism of action against C. hominivorax appears to be live larval expulsion. Additionally, the use of mechanical removal coupled with the lack of a control group confound the ability to define a pure treatment effect.

Effective Parasite Protection is Key

Even before NWS enters our country, veterinarians and pet owners can take precautions to prevent wounds that can create ideal conditions for NWS infection. NWS infestations begin when a female NWS fly lays eggs on open wounds or other parts of the body in live, warm-blooded animals. According to the Centers for Disease Control, wounds as small as a tick bite may attract a female fly to feed and lay her eggs. One female can lay 200 – 300 eggs at a time and may lay up to 1,000 eggs during her 10- to 30-day lifespan.ⁱⁱⁱ Unlike most fly species whose larvae may feed on dead and decaying tissue, NWS larvae burrow into the flesh of living animals, causing severe tissue damage and even death if left untreated.

The U.S. Animal Plant Health and Inspection Service (APHIS) recommends that one way to prevent NWS infestations is to protect pets and livestock from other wound-causing parasites such as flies and ticks.^iv

"Any break in the skin – from a scratch to a surgical incision – can become an entry point for NWS, due to its aggressive and invasive nature," said Dr. Casey Locklear, Texas-based veterinarian and parasiticide lead at Elanco. "Preventing or rapidly treating existing wounds is critical to protecting pets from NWS. One way to limit self-inflicted scratching includes using year-round flea and tick protection, such as Credelio."

Learn more about Credelio here.

To learn more about NWS, the following resources are available:

• FDA Information for Veterinarians on New World Screwworm
• USDA NWS Alert and Fact Sheet

ABOUT ELANCO
Elanco Animal Health Incorporated (NYSE: ELAN) is a global leader in animal health dedicated to innovating and delivering products and services to prevent and treat disease in farm animals and pets, creating value for farmers, pet owners, veterinarians, stakeholders and society as a whole. With 70 years of animal health heritage, we are committed to breaking boundaries and going beyond to help our customers improve the health of animals in their care, while also making a meaningful impact on our local and global communities. At Elanco, we are driven by our vision of Food and Companionship Enriching Life and our purpose – all to Go Beyond for Animals, Customers, Society and Our People. Learn more at www.elanco.com.

Emergency Use Authorization for Credelio (lotilaner) for New World screwworm (NWS)

The U.S. Food and Drug Administration (FDA) has issued an Emergency Use Authorization (EUA) for the emergency use of the approved product Credelio (lotilaner) for the treatment of infestations caused by NWS (Cochliomyia hominivorax) larvae (myiasis) in dogs and puppies. However, Credelio is not approved for this use.

Credelio is approved for other uses.

For additional information on the EUA, please refer to the Credelio NWS Fact Sheet.

Limitations of Authorized Use

Credelio (lotilaner) is authorized only for the duration of the declaration that circumstances exist justifying the authorization of the emergency use of Credelio (lotilaner) under section 564(b)(1) of the Federal Food, Drug, and Cosmetic Act (FD&C Act), 21 U.S.C. § 360bbb-3(b)(1), unless the authorization is terminated or revoked sooner.

CREDELIO INDICATIONS
Credelio kills adult fleas and is indicated for the treatment and prevention of flea infestations and treatment and control of tick infestations (lone star tick, American dog tick, black-legged tick, brown dog tick, and longhorned tick) for one month in dogs and puppies 8 weeks and older and 4.4 pounds or greater. Credelio is indicated for the prevention of Lyme disease infections as a direct result of killing black-legged ticks.

CREDELIO IMPORTANT SAFETY INFORMATION
Lotilaner is a member of the isoxazoline class of drugs. This class has been associated with neurologic adverse reactions including tremors, incoordination, and seizures. Seizures have been reported in dogs receiving this class of drugs, even in dogs without a history of seizures. Use with caution in dogs with a history of seizures or neurologic disorders. The safe use of Credelio in breeding, pregnant or lactating dogs has not been evaluated. The most frequently reported adverse reactions are weight loss, elevated blood urea nitrogen, increased urination, and diarrhea. For complete safety information, please see Credelio product label or ask your veterinarian.

Credelio, Elanco and the diagonal bar logo are trademarks of Elanco or its affiliates. Other company and product names are trademarks of their respective owners. © 2025 Elanco or its affiliates

ⁱ d do Vale, T.L., Costa, A.R., Miranda, L.M. et al. Efficacy of lotilaner against myiasis caused by Cochliomyia hominivorax (Diptera: Calliphoridae) in naturally infested dogs. Parasites Vectors 16, 86 (2023). https://doi.org/10.1186/s13071-023-05661-z
ⁱⁱ Mexico Confirms Case of New World Screwworm in Nuevo Leon | Animal and Plant Health Inspection Service
ⁱⁱⁱ About New World Screwworm Myiasis | Myiasis | CDC
^iv APHIS, New World Screwworm

Investor Contact: Tiffany Kanaga (765) 740-0314 tiffany.kanaga@elancoah.com
Media Contact: Season Solorio (765) 316-0233 season.solorio@elancoah.com  

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SOURCE Elanco Animal Health

FAQ

What did Elanco announce on October 24, 2025 about Credelio (ELAN)?

Elanco announced an FDA EUA authorizing Credelio to treat New World screwworm infestations in dogs.

How effective was Credelio against NWS in the study cited by Elanco?

The peer-reviewed study reported 100% efficacy against C. hominivorax larvae within 24 hours in 11 naturally infested dogs.

Does the FDA EUA for Credelio mean full approval for NWS in dogs?

No; an EUA authorizes use during an urgent need but is distinct from full FDA approval.

How close are confirmed New World screwworm cases to the U.S. border as of October 24, 2025?

Confirmed cases were reported at under 70 miles south of the U.S.-Mexico border.

What are the limitations of the data supporting Credelio for NWS treatment?

Limitations include a small sample (11 dogs), no control group, and mechanical removal that confounds pure treatment effect.

What should veterinarians and pet owners do to reduce NWS risk for dogs?

Prevent and promptly treat wounds and use year-round flea and tick protection to reduce conditions that attract NWS flies.