Elanco (NYSE: ELAN) secures FDA EUA for Credelio in fight against New World screwworm in dogs

Elanco Animal Health Incorporated (NYSE: ELAN) has received a historic authorization from the U.S. Food and Drug Administration, making it the first animal health company to secure Emergency Use Authorization for a parasiticide targeting New World screwworm infestations in dogs. The authorization allows veterinarians to use Elanco’s oral flea and tick treatment, Credelio (lotilaner), to treat infestations caused by the screwworm larvae Cochliomyia hominivorax under specific emergency conditions. While temporary in nature, this authorization is significant because it prepares the veterinary ecosystem to respond swiftly should the parasite cross into the United States.

The New World screwworm has been eradicated from the United States for decades, but confirmed cases have recently appeared less than 70 miles south of the U.S.–Mexico border. The parasite causes severe and sometimes fatal myiasis in warm‑blooded animals by feeding on living tissue. The decision to authorize treatment before confirmed domestic spread reflects a shift toward proactive outbreak preparedness in veterinary medicine.

Why did the FDA authorize Credelio for screwworm treatment prior to confirmed U.S. infections?

The U.S. Food and Drug Administration granted the Emergency Use Authorization under Section 564 of the Federal Food, Drug, and Cosmetic Act, which permits emergency use of products or indications that are not yet fully approved when there is a credible threat to animal or public health. The Secretary of Health and Human Services declared in August 2025 that the New World screwworm posed a significant potential threat, including risks to animal welfare, agricultural stability, and national biosecurity.

Credelio is already approved for the treatment and control of multiple tick species and the prevention of flea infestations in dogs and puppies. However, it had never been approved to treat screwworm myiasis. The emergency authorization bridges this regulatory gap, allowing veterinarians to prescribe the medication immediately should a suspected screwworm infestation occur.

The authorization is based on available scientific evidence suggesting Credelio may be effective in treating screwworm, combined with the absence of any adequate, approved, and accessible therapeutic alternative. In an emergency outbreak scenario, the absence of a viable treatment could lead to widespread and preventable animal suffering and fatality. Therefore, the agency determined the benefits outweigh the potential risks under controlled veterinary supervision.

What scientific and clinical evidence supports the use of Credelio against New World screwworm larvae?

The foundational evidence cited in the authorization stems from a 2023 field study conducted in Brazil and published in Parasites & Vectors. The study evaluated Credelio in eleven naturally infested dogs suffering from active screwworm myiasis. A single oral dose of lotilaner was administered to each dog based on standard body‑weight dosing. The study observed rapid larval expulsion, with more than 80 percent of larvae expelled within two hours of treatment and more than 93 percent expelled within six hours. By the 24‑hour mark, all larvae had either been expelled or manually removed, with no adverse reactions reported in any of the animals.

The study does have limitations. The population size was small, a control group was not included, and the use of mechanical larval removal makes it difficult to measure the drug’s isolated direct effect. The test population was also Brazilian, and its comparability to U.S. canine populations is unknown. Even so, the rapid expulsion of live larvae and the absence of reported adverse outcomes provided sufficient evidence to justify the emergency use in a preparedness context. The U.S. Food and Drug Administration noted that in the event of New World screwworm reestablishing itself in the United States, treatment urgency would outweigh the need for additional long‑term comparative data.

How does the authorization expand Credelio’s usage beyond its currently approved veterinary indications?

Under the terms of the authorization, veterinarians may prescribe Credelio for dogs and puppies of any age or weight, including animals that would fall below the product’s standard minimum weight or age threshold under regular label guidance. Use must occur under direct veterinary oversight, and administration should take place with food to support absorption.

Veterinarians may also prescribe Credelio to animals currently receiving other isoxazoline class parasiticides, provided a clinical risk‑benefit decision is made. The primary therapeutic function against screwworm appears to be rapid live larval expulsion, which is particularly critical given the aggressive and invasive nature of the parasite’s tissue‑destructive lifecycle.

How severe is the risk posed by New World screwworm to pets and livestock?

The biological threat posed by New World screwworm lies in the larvae’s ability to consume healthy, living tissue. Unlike most fly larvae, which feed on dead or decaying matter, New World screwworm larvae burrow into wounds as small as tick bites or scratches, causing progressive tissue loss, infection, and in severe cases, systemic shock or death. A single female screwworm fly can lay hundreds of eggs at a time and may deposit up to 1,000 eggs across multiple wound sites within a lifespan of just a few weeks.

The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service recommends year‑round ectoparasite control and vigilant wound care as primary lines of defense. Dr. Casey Locklear, a Texas‑based veterinarian and parasiticide lead at Elanco Animal Health Incorporated, noted that even routine scratching from flea irritation can create the type of micro‑abrasion that attracts a screwworm fly. This makes integrated flea and tick management essential to screwworm prevention, even before a confirmed domestic outbreak occurs.

What is the investor sentiment and market outlook for Elanco following the FDA EUA for Credelio?

Following the Emergency Use Authorization announcement, investor sentiment toward Elanco Animal Health Incorporated shifted modestly positive. Over the five trading sessions ending October 24, 2025, shares of Elanco increased to USD 22.05, marking a 1.80 percent gain across the five‑day period. In after‑hours trading, the stock moved higher to USD 22.53, representing an additional 2.18 percent rise, suggesting that the market responded constructively to the regulatory development.

The move reflects measured confidence rather than aggressive momentum. Trading volumes increased moderately, indicating that institutional investors are evaluating the EUA as a sign of the company’s operational readiness rather than a guaranteed revenue catalyst. Analysts tracking the stock have described the authorization as reputationally accretive and strategically beneficial, particularly in the context of Elanco’s broader parasiticide portfolio.

Retail investor discussions across financial forums and social platforms show cautious optimism, with some viewing the EUA as reinforcing the company’s scientific credibility, while others note that material revenue impact depends on whether screwworm establishes a measurable presence within U.S. borders. Domestic institutional funds appear to be maintaining exposure, while foreign institutional flows remain stable. The stock is currently viewed as Hold with an upward bias, with potential for near‑term appreciation should additional regulatory or clinical milestones follow.

How will Elanco and veterinary clinics manage distribution and ongoing safety monitoring under the EUA?

The Emergency Use Authorization mandates that all Credelio units distributed for screwworm treatment be accompanied by the official veterinary fact sheet outlining dosage, storage, and reporting procedures. Veterinary clinics are required to document product dispensation, maintain treatment logs, and report any adverse events through established FDA reporting channels. These records must be maintained for a minimum period following termination of the authorization.

Elanco Animal Health Incorporated is required to ensure accurate distribution oversight, clear product labeling indicating emergency authorization status, and accessibility of educational materials for veterinary professionals. Promotional communications must accurately state that Credelio is not FDA‑approved for screwworm treatment but is authorized for emergency use under the declared conditions.

What does the EUA mean for Elanco and the broader animal health industry?

For Elanco Animal Health Incorporated, the authorization enhances its strategic positioning in the companion animal parasiticide market and reinforces its regulatory credibility. The move underscores a broader shift in animal health governance, one that favors preemptive readiness and flexible application of known therapeutics in emergency contexts. Should New World screwworm spread into the United States, Elanco will be first in position with an authorized treatment pathway, providing both clinical relevance and potential commercial advantage.

Across the sector, the EUA may signal the beginning of more dynamic regulatory frameworks in veterinary medicine, particularly for fast‑moving parasitic and zoonotic threats. The authorization aligns Elanco more closely with federal public health and agricultural agencies, potentially expanding future collaboration opportunities in disease surveillance, treatment strategy, and emergency response planning.

What are the key takeaways from Elanco’s FDA emergency use authorization for Credelio in New World screwworm?

• Elanco Animal Health Incorporated (NYSE: ELAN) received an Emergency Use Authorization (EUA) from the U.S. Food and Drug Administration to use Credelio (lotilaner) for treating New World screwworm (Cochliomyia hominivorax) infestations in dogs.
• This marks the first-ever FDA EUA for New World screwworm treatment in companion animals and comes despite the fly not yet entering U.S. territory.
• The EUA allows veterinarians to use Credelio in dogs of all ages and weights, even below the standard approved range, under specific emergency scenarios.
• The authorization was based on a 2023 Brazilian study showing 100% larval expulsion within 24 hours of dosing, though limitations included a small sample size and no control group.
• Credelio’s primary mechanism of action in this context is live larval expulsion, making it suitable for rapid-response parasite management.
• The New World screwworm poses a fatal risk to dogs through live tissue infestation, often entering through minor wounds or scratches.
• Elanco must comply with strict FDA EUA conditions around labeling, adverse event reporting, and educational dissemination to veterinarians.
• Investor sentiment around the EUA has been cautiously positive, with Elanco stock (NYSE: ELAN) rising 1.8% over five days and gaining an additional 2.18% in after-hours trading post-announcement.
• Analysts maintain a Hold rating with short-term upside bias, while institutional flows remain neutral to slightly positive.