FDA Authorizes Nitenpyram for New World Screwworm Prevention in Dogs and Cats, Marking First Prophylactic Option for Pets
Executive Summary: On September 3, 2026, the FDA issued an emergency use authorization for Capstar (nitenpyram) tablets and revised the existing EUA for generic nitenpyram tablets to allow prevention, not just treatment, of New World screwworm myiasis in dogs and cats. The authorization applies to animals weighing at least 2 pounds and 4 weeks of age, making over-the-counter nitenpyram the first FDA-authorized preventive drug against the parasite in companion animals. The move comes as confirmed domestic cases reach 48 across goats, sheep, cattle, and 3 dogs, with APHIS releasing two Texas zones from restrictions the day prior.
Key Facts
- Company
- FDA Center for Veterinary Medicine
- Country
- United States
- Industry
- Pet pharmaceuticals, veterinary regulation
- Category
- Emergency use authorization, parasiticide
- Event
- First FDA-authorized prevention option for NWS in dogs and cats
- Date
- 2026-09-03
- Location
- United States (NWS cases concentrated in Texas)
- Source
- FDA Center for Veterinary Medicine
What Happened
On September 3, 2026, the FDA issued an emergency use authorization (EUA) for Capstar (nitenpyram) tablets and revised the EUA for generic nitenpyram tablets to permit their use for preventing New World screwworm (NWS) myiasis in dogs and cats. The generic nitenpyram product received its initial EUA in June 2026 for treatment only. The expanded authorization now covers both prevention and treatment, available over the counter in 11.4-mg and 57-mg tablet strengths.
The EUAs apply to dogs, puppies, cats, and kittens weighing at least 2 pounds and at least 4 weeks old. Dosing is based on body weight. The FDA stated that its authorization is based on the totality of available scientific evidence, concluding that the products may be effective for prevention and treatment and that their benefits outweigh their risks.
Timothy Schell, PhD, director of the FDA Center for Veterinary Medicine, said: “Although the FDA has authorized or conditionally approved multiple products for the treatment of New World screwworm in dogs and cats, none were for prevention — until today. The FDA is addressing a previously unmet need and giving pet owners and veterinarians important tools to protect dogs and cats from NWS infestations.”
Background
New World screwworm, caused by larvae of the parasitic fly Cochliomyia hominivorax, infests warm-blooded animals. Female flies lay eggs in or around wounds or mucous membranes, and the resulting larvae feed on living tissue. Infestations can cause severe tissue damage and may be fatal if left untreated. The parasite was eradicated from the United States in 1966 but reemerged in 2026, with the first domestic detection in a Zavala County, Texas calf on June 3.
As of September 3, 2026, the USDA Animal and Plant Health Inspection Service (APHIS) has confirmed 48 domestic NWS cases in goats, sheep, cattle, and 3 dogs. On September 2, APHIS released two Texas zones from NWS-related movement restrictions, marking the first infested-zone releases since the initial detection. The FDA has now issued 15 EUAs and 3 conditional approvals for animal drugs against NWS.
Industry Context
The nitenpyram EUA expansion intersects with several segments of the pet industry value chain. As an over-the-counter parasiticide, nitenpyram flows through pet pharmacy and retail channels rather than requiring a veterinary prescription. The pet meds market, already a high-volume category, may see increased demand in Texas and border states where NWS risk is elevated.
The authorization also highlights the regulatory pathway for emergency animal drug approvals. Unlike standard FDA approvals, EUAs are issued when the Secretary of Health and Human Services declares that circumstances justify emergency use. The nitenpyram EUAs will remain in effect until revoked or until the emergency declaration is terminated.
Market and Business Impact
The NWS reemergence has created a new category of regulatory response focused on companion animal prevention. Prior to this authorization, pet owners in affected areas had no FDA-authorized prophylactic option. The 48 confirmed domestic cases, including 3 in dogs, indicate that the parasite has crossed from livestock into companion animals.
For pet pharmaceutical manufacturers, the EUA framework opens a temporary regulatory pathway for repurposing existing products. Nitenpyram, originally marketed as Capstar for flea control, now carries a dual indication. The generic nitenpyram tablets authorized in June 2026 were the first generic animal drug authorized under an FDA EUA for NWS treatment.
Companies and Brands Involved
The primary drug products are Capstar (nitenpyram) tablets, manufactured by Elanco, and generic nitenpyram tablets. The FDA Center for Veterinary Medicine issued the EUA. APHIS manages the field response, including surveillance, zone quarantines, and movement restrictions in Texas.
Data and Evidence
- 48 confirmed domestic NWS cases (goats, sheep, cattle, 3 dogs) as of September 3, 2026 (USDA APHIS)
- 15 EUAs and 3 conditional approvals for animal drugs against NWS issued by FDA to date
- EUA applies to animals weighing at least 2 pounds, at least 4 weeks old (FDA)
- 11.4-mg and 57-mg tablet strengths available over the counter (FDA)
What This Means for the Pet Industry
The FDA’s decision to authorize prevention of New World screwworm in companion animals reflects a regulatory system adapting to a resurgent biological threat. For the pet industry, the key signal is that over-the-counter parasiticides are being repurposed for emergency prophylaxis, which may shift demand patterns in affected regions. The more significant long-term question is whether NWS becomes endemic in the United States, which would permanently alter the parasiticide market for dogs and cats in southern states. For now, the immediate impact is limited to Texas and border areas, but the regulatory precedent of using EUAs for pet parasiticides is established.
Key Takeaways
- The FDA authorized Capstar (nitenpyram) and generic nitenpyram tablets for prevention of New World screwworm in dogs and cats on September 3, 2026, marking the first prophylactic option for pets.
- The EUAs apply to animals weighing at least 2 pounds and 4 weeks of age, with both 11.4-mg and 57-mg over-the-counter tablets available.
- APHIS confirmed 48 domestic NWS cases including 3 dogs, and released two Texas zones from restrictions on September 2, 2026.
- The FDA has issued 15 EUAs and 3 conditional approvals for animal drugs against NWS since the parasite’s reemergence.
- The authorization creates a new regulatory pathway for emergency prophylactic use of OTC parasiticides in companion animals.
Frequently Asked Questions
What did the FDA authorize for New World screwworm prevention in pets?
The FDA issued an emergency use authorization for Capstar (nitenpyram) tablets and revised the EUA for generic nitenpyram tablets to allow both prevention and treatment of New World screwworm myiasis in dogs and cats weighing at least 2 pounds and at least 4 weeks old.
Which animals are at risk of New World screwworm in the United States?
Most dogs and cats in the US face a low risk of exposure. Risk is higher for animals living in, traveling to, or returning from areas where NWS infestations have been identified, particularly in Texas. To date, 48 domestic cases have been confirmed in goats, sheep, cattle, and 3 dogs.
Is nitenpyram available over the counter or does it require a prescription?
Both Capstar and generic nitenpyram tablets are available over the counter in 11.4-mg and 57-mg tablet strengths, with dosing based on body weight. No prescription is required under the EUA.
Why is this authorization significant for the pet industry?
This is the first FDA-authorized prevention option for New World screwworm in dogs and cats. It creates a regulatory pathway for emergency prophylactic use of OTC parasiticides in companion animals and may affect demand for pet pharmacy products in affected regions.
What pet industry segment is affected by this authorization?
The pet pharmaceutical and pet pharmacy segments are most directly affected, particularly over-the-counter parasiticide distribution channels in Texas and border states. Veterinary clinics and low cost vet services in affected areas may also see increased demand for NWS screening.
Sources
- Primary — FDA Center for Veterinary Medicine, “FDA Issues Emergency Use Authorization for Drugs to Prevent and Treat New World Screwworm in Dogs and Cats,” September 3, 2026, https://www.fda.gov/news-events/press-announcements/fda-issues-emergency-use-authorization-drugs-prevent-and-treat-new-world-screwworm-dogs-and-cats
- Secondary — dvm360, “FDA emergency authorizes Capstar, generic nitenpyram to prevent and treat New World screwworm in dogs and cats,” September 3, 2026, https://www.dvm360.com/view/fda-emergency-authorizes-capstar-generic-nitenpyram-prevent-and-treat-new-world-screwworm-dogs-and-cats
- Secondary — USDA APHIS, “Confirmed Detections of New World Screwworm,” September 2026, https://www.aphis.usda.gov/animals/animal-health/livestock-and-poultry-disease/stop-screwworm/current-status/confirmed
