The U.S. Food and Drug Administration has granted emergency use authorization for nitenpyram, a medication used to treat New World screwworm infestations in dogs and cats. The action marks the first approval of a generic animal drug specifically authorized for use against the flesh-eating parasite.

Nitenpyram tablets may be used in dogs and cats that are at least four weeks old and weigh at least two pounds. The medication was originally approved by the FDA in 2000 under the brand name Capstar for the treatment of fleas.

The New World screwworm is a dangerous parasite whose larvae feed on living flesh and bodily fluids. Female flies lay eggs in open wounds or mucous membranes, and the resulting larvae can infest virtually any warm-blooded animal, including livestock, pets, wildlife, and in rare cases, humans.

According to the FDA, studies conducted in Brazil found that most screwworm larvae were expelled from infected dogs and cats after treatment with nitenpyram, while any remaining larvae died shortly afterward. Veterinarians may still need to remove dead or surviving larvae following treatment.

The authorization comes as officials monitor new cases of New World screwworm in the United States. While the pest was considered eradicated in the country decades ago, recent infestations have been reported in cattle in Texas and in a dog in New Mexico.

FDA officials said nitenpyram acts quickly, killing most screwworm larvae within hours of the first dose. Pet owners are advised to administer a second dose six hours after the initial treatment. However, the agency cautioned that the medication does not provide long-term protection against future infestations.

The FDA said emergency use authorization allows faster access to treatments during urgent situations and is intended to help veterinarians and pet owners respond more effectively to screwworm outbreaks.