AHN Highlights
- Authorization: First FDA Emergency Use Authorization for NWS in dogs
- Indication: Treatment of New World screwworm infestations
- Mode of Action: Oral isoxazoline that kills larvae within 24 hours
- Study basis: 11 naturally infested dogs in Brazil; 100% efficacy observed
- Threat level: NWS cases confirmed near the U.S.–Mexico border
- Prevention: Year-round flea and tick protection reduces risk of wound infestation
The U.S. Food and Drug Administration (FDA) has granted Elanco Animal Health an Emergency Use Authorization (EUA) for Credelio™ (lotilaner) to treat New World screwworm (NWS) infestations in dogs. It is the first FDA authorization ever issued for NWS in dogs, providing veterinarians and pet owners with a treatment option should the fly enter the United States.
Confirmed NWS cases have been detected less than 70 miles south of the U.S.–Mexico border, prompting proactive regulatory action to prepare for possible spread.
“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,” said Dr. Ellen de Brabander, Executive Vice President of Innovation and Regulatory Affairs at Elanco.
The authorization was based on a peer-reviewed study published in Parasites & Vectors showing that Credelio eliminated 100% of NWS larvae within 24 hours after oral administration at the recommended dose in naturally infested dogs. The study included 11 dogs in Brazil and demonstrated rapid larval expulsion as the primary mode of action.
While the data are limited, the EUA ensures availability of treatment in the event of U.S. detection.
Understanding the Threat of New World Screwworm
New World screwworm (Cochliomyia hominivorax) is an invasive fly species whose larvae feed on living tissue, unlike most flies that target decaying matter. Infections begin when a female lays eggs in open wounds or skin lesions; larvae can cause severe tissue destruction and potentially fatal infections if untreated.
A single female can lay up to 1,000 eggs over her lifespan, and wounds as small as a tick bite can attract the flies. The U.S. Animal and Plant Health Inspection Service (APHIS) warns that preventing open wounds and maintaining year-round parasite control are key preventive measures.
“Any break in the skin—from a scratch to a surgical incision—can become an entry point for NWS,” said Dr. Casey Locklear, a Texas-based veterinarian and parasiticide lead at Elanco. “Preventing or rapidly treating wounds is critical to protecting pets, and effective flea and tick control products like Credelio can help reduce the risk.”
