These flies are not like their relatives that feed on dead and decaying animals. No, the flesh-eating maggots of these parasitic insects prefer to feed on live animals such as cattle, horses and pigs and can be fatal.
Another case of the New World worm was recently stopped from entering the United States at a quarantine facility in Florida.
And humans are not immune. A traveler returned to the United States from Central America last summer carrying the parasite.
Maggots enter through open wounds and mucous membranes. They burrow or screw into an animal’s flesh using “sharp mouth hooks,” according to the Animal and Plant Health Inspection Service. This is how the New World Worm got its name.
Is the New World Worm in the United States? How close is it to Ohio? Here’s what you need to know.
The fang-like mandibles that protrude from the mouth of the screwworm larva snatch the flesh of living warm-blooded animals. A wound can contain hundreds of such larvae.
“Critical Threat” to US Agriculture: How USDA Prepares for New World Worm
New World worm casing found in Florida facility
According to the Florida Department of Agriculture and Consumer Services, screwworm larvae were detected earlier this month on a horse imported from Argentina undergoing routine examination and required at an approved USDA import facility in South Florida.
There was no detection of NWS larvae outside the quarantine facility. The affected horse was treated, and out of an abundance of caution, the agency said in a statement that all horses in the cohort at the facility were also examined and treated.
“There is no detection of New World Worm in any Florida animal. The detection at the USDA import facility was handled professionally and according to existing protocols to ensure the US remains free of this devastating pest,” state veterinarian Dr. Michael Short said in the statement.
The infected horse had to remain in quarantine until it was re-examined and found to be free of parasites.
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Is the New World Worm in the United States or Ohio?
The insect was eradicated in the US in the 1960s, Mexico in the 1970s and much of Central America in the early 2000s, according to the Centers for Disease Control and Prevention, USA TODAY reported.
However, the CDC said new cases were reported in October 2024 in Panama, Costa Rica, Nicaragua and Honduras. From there, it spread north, raising fears that the insects would spread north into the United States. Their move prompted the US to block imports of live cattle, horses and bison through southern border ports, USA TODAY reports.
ScienceAlert.com reported that as of January 2026, there were 601 active animal cases in Mexico, eight of which were in Tamaulipas—a state bordering Texas.
According to the USDA’s Animal and Plant Health Inspection Service, the New World cutworm is not currently present in the U.S.
The closest it came to Ohio is a human case in Maryland from a traveler who returned from El Salvador in 2025.
What is so dangerous about the New World worm fly?
NWS flies are about the size of a common housefly and lay eggs “on open wounds or other open body parts in live, warm-blooded animals,” according to the CDC. A wound as small as a tick bite can attract flies.
The eggs hatch and the larvae burrow into the wound to feed on the living flesh, the CDC says. As you might expect, burrowing in living creatures is extremely painful.
After feeding, the larvae fall to the ground and burrow into it. Later, they emerge as adult screwworm flies, the CDC says.
New World worms in humans – what are the symptoms?
NWS infestations are very painful, according to the USDA. If you have an infestation, you may see worms around or in an open wound, or in your nose, eyes or mouth. Symptoms may include:
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Unexplained skin lesions (wounds or wounds) that do not heal.
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Skin wounds or sores that get worse over time.
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Painful sores or wounds on the skin.
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Bleeding from open wounds.
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Sensation of larvae moving in a wound or pain in the skin, nose, mouth or eyes.
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Seeing worms around or in open wounds.
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A foul-smelling odor from the site of the infestation.
Male sterile screwworm fly marked with a numbered tag to study fly dispersal, behavior and longevity.
The US plans to prevent the spread of the screwworm
The USDA’s plan to prevent the spread of the screwworm includes investing up to $100 million in innovation to find new ways to combat the bug and $750 million to create a facility in South Texas to sterilize the flies and combat the spread, USA TODAY reported in September 2025.
Releasing sterile flies to disrupt screwworm reproduction was a technique used to eradicate the pest in the 1960s. The hope is that those sterile flies will then mate with wild ones, producing sterile eggs, experts said.
Another $21 million is being invested to renovate an existing fruit fly production facility in Metapa, Mexico, to produce more sterile flies.
This article originally appeared on The Columbus Dispatch: Flesh-eating parasite targets US. Is Ohio safe? More about the New World