FDA Grants Emergency Use of Nitenpyram for Screwworm in Pets

U.S. Food and Drug Administration granted emergency use authorization for nitenpyram to treat New World screwworm infestations in dogs and cats. The agency issued the authorization in a statement on Thursday.

Nitenpyram is the first generic animal drug approved for use against the flesh-eating parasite. The tablets can be used in dogs and cats that weigh at least two pounds and are at least four weeks old. The medication was previously approved by the FDA in 2000 under the brand name Capstar for treating fleas.

The agency relies on emergency use authorizations to speed access to treatments in urgent situations. New World screwworm larvae eat live flesh and fluids instead of dead material. Female flies lay eggs in open wounds and mucous membranes after mating only once in their monthslong lives.

The larvae can infest any warm-blooded animal, including wildlife, pets and occasionally humans. Studies in Brazil on cats and dogs with screwworm infestations found that most of the maggots were expelled after treatment with nitenpyram, while the remaining larvae died, according to an FDA fact sheet.

After receiving the tablets, an animal may need to have remaining live or dead larvae removed by a veterinarian.

"Nitenpyram works quickly, killing most [screwworm] larvae within hours of the first dose," the FDA said on Thursday. " Because the drug's effects are short-acting, it does not provide ongoing protection against new infestations, the agency added. U.S. Several new cases have been found in cattle in Texas in recent weeks, as well as in a dog in New Mexico, according to government officials.