FDA issues emergency use authorization for drugs to prevent and treat New World screwworm in dogs and cats
The U.S. Food and Drug Administration issued an Emergency Use Authorization on September 3, 2026, allowing Capstar and generic Nitenpyram tablets to prevent and treat New World screwworm infestations in dogs and cats weighing at least 2 pounds across the United States. Officials said the authorization expands prior treatment-only approvals to include prevention as part of a federal response to the potential public health emergency posed by the parasite.
This marks an expansion from earlier Emergency Use Authorizations (EUAs) that permitted these drugs solely for treatment of New World screwworm (NWS) infestations, caused by *Cochliomyia hominivorax* larvae, to now include prevention in companion animals nationwide. The FDA’s action is part of the federal government’s response to a potential public health emergency posed by the invasive parasite, officials said.
The authorization covers Capstar (nitenpyram) tablets and generic Nitenpyram tablets for use in dogs, puppies, cats, and kittens weighing at least 2 pounds and at least 4 weeks old, according to FDA documents dated September 3, 2026.
The FDA issued the original EUA for generic Nitenpyram tablets on June 11, 2026, authorizing their use for treatment of NWS in dogs and cats. The September 3 revision aligns the generic product’s indication with Capstar’s, which received its first EUA for both prevention and treatment on the same day. Both authorizations were granted under section 564 of the Federal Food, Drug, and Cosmetic Act, the same legal authority used for human medical countermeasures, FDA records show. The agency concluded that the benefits of emergency use outweigh known and potential risks in the context of the NWS public health emergency, according to the EUA letters to manufacturers.
Earlier in 2026, the FDA authorized other drugs for treatment of NWS infestations in dogs and cats. On February 18, the agency issued EUAs for NexGard (afoxolaner) chewable tablets for dogs and NexGard COMBO (esafoxolaner, eprinomectin, and praziquantel topical solution) for cats, both limited to treatment, not prevention, of screwworm myiasis. Boehringer Ingelheim, the manufacturer, confirmed these authorizations in a corporate release dated February 19, 2026, emphasizing support for veterinarians and pet owners managing NWS cases. Additionally, Simparica TRIO (sarolaner, moxidectin, and pyrantel chewable tablets) received an EUA on August 13, 2026, for treatment of NWS infestations in dogs and puppies only, with no preventive indication. USDA’s Animal and Plant Health Inspection Service (APHIS) also announced this authorization on the same date.
According to FDA’s “Animal Drugs for New World Screwworm” webpage, as of September 3, 2026, the agency has issued 15 EUAs and three conditional approvals for animal drugs targeting NWS across multiple species, including companion animals, livestock, birds, and exotic mammals. These regulatory actions are contingent on a declaration by the Department of Health and Human Services that the potential public health emergency posed by NWS justifies emergency use authorizations for animal drugs. FDA and USDA APHIS coordinate communications to veterinarians and industry stakeholders, directing them to official FDA pages listing authorized drugs and relevant documentation such as letters of authorization, fact sheets, and environmental assessments.
The scope of the EUAs varies by product and species. Capstar and generic Nitenpyram tablets are authorized for both prevention and treatment in dogs, puppies, cats, and kittens meeting weight and age criteria. NexGard and NexGard COMBO EUAs remain limited to treatment in dogs and cats, respectively, without preventive use. Simparica TRIO’s EUA covers treatment only in dogs and puppies. The FDA has also authorized F10 Antiseptic Wound Spray with Insecticide for prevention and treatment of NWS in multiple species but explicitly prohibits its use in domestic dogs and cats. Federal communications emphasize that use outside the authorized species or indications is not permitted under the emergency provisions.
The FDA advises veterinarians to consult detailed fact sheets and letters of authorization for guidance on dosage, safety, and administration of these drugs under the EUAs. The agency’s September 3 announcement highlighted the shift toward prophylactic management of at-risk dogs and cats in areas affected or threatened by NWS. The invasive screwworm larvae cause myiasis, a condition that can be fatal if untreated, prompting the federal emergency declarations and regulatory responses.
The EUAs remain effective until revoked by the FDA or until the Secretary of Health and Human Services terminates the underlying emergency declaration related to NWS. The ongoing federal response reflects efforts to control and prevent spread of the parasite in the United States, involving multiple authorized drugs and coordinated veterinary guidance.
