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The U.S. Food and Drug Administration has approved the emergency use of an over-the-counter animal drug to treat infections of New World screwworm, a potentially deadly parasite in cats and dogs.
The announcement comes after two states noted New World screwworm infections. In Texas, the parasite was detected in cows and goats, and in New Mexico, a dog was infected.
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These are the first noted cases in animals since at least 2017, when a small outbreak was found and eradicated in Florida, according to the U.S. Department of Agriculture (USDA).
This image shows screwworm larvae.
(CDC / FOX Weather)
The first case this month was found in the umbilicus of a 3-week-old calf in Texas.
The FDA said generic Nitenpyram Tablets (nitenpyram) can be used for the treatment of New World screwworm infestations in dogs, puppies, cats and kittens that weigh at least two pounds and are at least four weeks old.
The New World screwworm is a parasitic fly species that feeds on the tissue or flesh of warm-blooded animals and people to complete parts of its life cycle, the Centers for Disease Control and Prevention (CDC) said.
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New World screwworm
(USDA via APHIS / FOX Weather)
The infestation begins when adult females are attracted to open wounds and body openings, such as the eyes, nose, mouth or genitals.
They lay their eggs — usually 200 to 300 at a time — in these vulnerable areas, which quickly hatch into maggots that burrow into the wound or opening to feed on the flesh, a painful condition known as myiasis.
Nitenpyram is the first animal drug available to treat New World screwworm, the FDA said.
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“The FDA has spent nearly a year fast-tracking reviews and readying for the arrival of New World screwworm in the U.S.,” said Acting FDA Commissioner Kyle Diamantas.
AUSTIN, TEXAS – JUNE 5: A poster with information on the New World Screwworm is displayed during a press conference with government officials at the Texas Division of Emergency Management State Operations Center on June 5, 2026 in Austin, Texas.
(Joel Angel Juarez / Getty Images)
The FDA said nitenpyram works quickly, killing most larvae within hours of the first dose. A second dose should be administered six hours after the first. Dosage amounts are based on the pet’s weight.
Because the effects are short-acting, Nitenpyram Tablets do not prevent NWS myiasis or protect against reinfestation, the FDA said.
“Following treatment with Nitenpyram Tablets, a veterinary professional may need to physically remove any remaining live or dead larvae,” the FDA said. “This task is best performed by someone with training in veterinary medicine to minimize the risk of infection or further tissue damage.”
