WASHINGTON, D.C. — The U.S. Food and Drug Administration has authorized the first generic animal drug for treating New World screwworm infestations in dogs and cats, expanding the federal government’s response as officials prepare for the potential spread of the destructive parasite within the United States.
The agency issued an Emergency Use Authorization for generic Nitenpyram Tablets, permitting their use in dogs, puppies, cats and kittens at least four weeks old and weighing at least two pounds. The authorization allows veterinarians and pet owners to use the over-the-counter treatment against New World screwworm myiasis, a parasitic infestation caused by fly larvae that feed on living tissue.
The decision adds another tool to a federal response effort that has intensified since health officials declared an animal health emergency related to New World screwworm in 2025.
According to the FDA, available scientific evidence indicates the drug may be effective in treating infestations, and the agency determined that its potential benefits outweigh known and potential risks under emergency-use provisions.
Acting FDA Commissioner Kyle Diamantas noted that the agency has accelerated reviews related to New World screwworm preparedness over the past year. He stated that the FDA has now issued ten emergency use authorizations and three conditional approvals for animal drugs intended to address the threat.
New World screwworm flies lay eggs in wounds or mucous membranes of mammals. Once hatched, the larvae burrow into living tissue, causing potentially severe damage if left untreated.
The FDA reported that nitenpyram acts rapidly, killing most larvae within hours of administration. A second dose is recommended six hours after the initial treatment.
Because the medication is short-acting, it does not prevent future infestations or protect animals from reinfestation, the agency noted.
Federal officials also cautioned that veterinary intervention may still be required after treatment. Remaining live or dead larvae may need to be physically removed, and veterinarians may recommend additional wound care to reduce the risk of infection and recurring infestations.
Nitenpyram Tablets are available without a prescription in 11.4-milligram and 57-milligram formulations, with dosage determined by an animal’s weight. The FDA advises that the product should not be administered to dogs or cats weighing less than two pounds.
The authorization comes as federal agencies continue coordinating efforts to contain and eradicate New World screwworm, a pest that was previously eliminated from the United States but remains a significant concern for livestock, wildlife and companion animals.
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