On June 11, the FDA announced an Emergency Use Authorization for generic Nitenpyram Tablets to treat New World screwworm infestations, or myiasis, in dogs, puppies, cats, and kittens weighing at least two pounds and at least four weeks old.
This is the first time a generic animal drug has been authorized for use against New World screwworm.
“The U.S. government is moving aggressively to contain and eliminate New World screwworm,” Health and Human Services Secretary Robert F. Kennedy Jr. said in a statement. He said the authorization provides pet owners with an affordable treatment option, strengthens containment strategies, and helps stop the destructive parasite from spreading further in the U.S.
Animals that have recently traveled to or been located in areas with confirmed New World screwworm cases face a higher risk of infestation.
New World screwworm flies lay eggs in open wounds or mucous membranes of mammals. After hatching, the larvae burrow into living tissue and feed on flesh, causing painful wounds that can become severe if untreated.
According to the FDA, Nitenpyram acts quickly and is expected to kill most screwworm larvae within hours of the first dose. Pet owners should give a second dose six hours later. The FDA cautioned the drug does not prevent future infestations or protect animals from being reinfested.
Veterinarians may still need to remove any remaining live or dead larvae and provide wound care after treatment, the FDA said, advising pet owners to consult a veterinarian to minimize the risk of infection and further tissue damage.
The authorization comes as federal and state officials respond to the first confirmed domestic cases of New World screwworm in more than six decades.
Earlier this month, U.S. agriculture officials confirmed infestations in cattle, a goat, and a dog in Texas and New Mexico. On Monday, officials announced three more cases, bringing the total number of confirmed U.S. cases to five since the first infected calf was identified in Texas.
The parasite poses a significant threat to livestock, pets, wildlife and, in rare cases, humans. Unlike most fly larvae that feed on dead tissue, New World screwworm larvae consume living flesh. Experts warn that untreated infestations can cause severe injury or death.
Federal officials have been tracking the parasite’s northward movement since cases reappeared in southern Mexico in 2024. The pest was eradicated from the United States in 1966 through a large-scale sterile fly release program.
The U.S. Department of Agriculture has expanded that strategy in recent months, releasing millions of sterile flies across South Texas and investing in new production facilities in Texas and Mexico to slow the parasite's spread.
Nitenpyram Tablets are available without a prescription in 11.4- and 57-milligram doses. The product is sponsored by Felix Pharmaceuticals Pvt. Ltd. of Ireland.