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CDC, FDA Tackle New World Screwworm Including Drug Authorization
- June 16, 2026
- Ellyn Vohnoutka HealthDay Reporter
Federal health officials are mobilizing against the New World screwworm, a flesh-eating parasite recently detected in animals in the southwest United States.
The U.S. Centers for Disease Control and Prevention (CDC) has activated an emergency operations center to coordinate its response. The agency is supporting the U.S. Department of Agriculture (USDA) and Texas health officials after the parasite was found in animals in southern Texas and in one county in New Mexico.
As of June 11, the USDA reports 12 screwworm cases in domestic animals, including sheep, cattle and goats.
New World screwworm is the larva of a fly that lays its eggs in open wounds or body openings of mammals. The eggs hatch within hours, and the maggots burrow into living flesh, a painful infestation known as myiasis.
The parasite mainly threatens livestock, pets and wildlife, but can also infest humans. So far, no human cases have been reported in the United States, and the CDC says the risk to the public remains low. The danger is greatest for people and animals in areas where the flies are active.
There is also reassuring news about how it spreads. The parasite "cannot spread from animal to animal, animal to people, or person to person," the CDC said. Infestation happens only when flies lay eggs directly in a wound or opening.
On the same day the CDC ramped up its response, the U.S. Food and Drug Administration (FDA) cleared a new treatment for affected pets.
The agency issued an emergency use authorization for generic nitenpyram tablets to treat screwworm in dogs, puppies, cats and kittens.
It is the first generic animal drug authorized against the parasite.
The medication is sold over the counter in two tablet sizes, with dosing based on the animal's weight. It works fast, killing most larvae within hours. Pet owners must give a second dose six hours after the first. The drug is short-acting, however, so it does not prevent future infestations, according to the FDA.
Because the tablets do not remove larvae, a veterinarian may still need to remove any that remain.
“Generic animal drugs build resilience in our domestic supply chain and play a critical role in expanding the toolkit of U.S. veterinary drugs for New World screwworm,” said Timothy Schell, director of the FDA’s Center for Veterinary Medicine. “By authorizing this generic treatment, FDA is reinforcing our commitment to providing timely, affordable options to safeguard animal health for American pet owners.”
The FDA advises owners to consult a vet for wound care and to prevent reinfestation. Pet owners should not give this drug to animals that weigh less than 2 pounds or are younger than 4 weeks old.
New World screwworm has been eradicated in the United States before, and CDC officials say they aim to do it again. Doctors and veterinarians in affected areas are being urged to watch for signs of infestation and report suspected cases to state health or animal health authorities.
More information
The U.S. Centers for Disease Control and Prevention has more on New World screwworm infection.
SOURCES: U.S. Centers for Disease Control and Prevention, June 12, 2026; U.S. Food and Drug Administration, June 11, 2026; U.S. Department of Agriculture, June 11, 2026
