"C. hominivorax is a species of parasitic fly that lays eggs inside the open wounds, eyes, noses or mouths of warm-blooded animals. Female screwworm flies can lay up to 300 eggs at a time. When the eggs hatch, screwworm larvae use their sharp mouths to burrow into the host's flesh, which causes a painful infestation called myiasis." Wounds as small as a tick bite may attract a female fly to feed and lay her eggs. One female can lay 200 – 300 eggs at a time and may lay up to 3,000 eggs during her 10- to 30-day lifespan.
This is primarily a concern for livestock, but as with this case, people can become infected. The symptoms include: feeling larvae movement within a skin wound or sore, nose, mouth, or eyes: seeing maggots around or in open sores; a foul-smelling odor from the site of the infestation.
The New World screwworm is endemic to South America and the Caribbean, and it isn't typically found in the U.S. However, there has been a northward movement with an infestation in Mexico in 2024.
Live Science
https://www.livescience.com/health/viruses-infections-disease/us-reports-its-first-new-world-parasitic-screwworm-infection-in-decades
US reports its first New World parasitic screwworm infection in decades
A person in Maryland has been diagnosed with an infection of the flesh-eating New World screwworm. It's the first case in the U.S. in decades.
A person in Maryland has been confirmed to have an infection with the flesh-eating New World screwworm parasite — the first human case of the infection in the United States since the parasite was eradicated in the country over 60 years ago, according to the U.S. Department of Health and Human Services (HHS).
The Maryland patient had returned to the U.S. after traveling to El Salvador, HHS spokesperson Andrew G. Nixon told Reuters in an email, and the Centers for Disease Control and Prevention (CDC) confirmed the infection with the New World screwworm (Cochliomyia hominivorax) via images of the larvae on Aug. 4, according to Axios.
"This is the first human case of travel-associated New World screwworm myiasis (parasitic infestation of fly larvae) from an outbreak-affected country identified in the United States," Nixon said in an emailed statement to Axios. However, "the risk to public health in the United States from this introduction is very low," he added.
C. hominivorax is a species of parasitic fly that lays eggs inside the open wounds, eyes, noses or mouths of warm-blooded animals. Female screwworm flies can lay up to 300 eggs at a time. When the eggs hatch, screwworm larvae use their sharp mouths to burrow into the host's flesh, which causes a painful infestation called myiasis.
New World screwworms primarily affect cattle and other livestock, but they can also cause infestations in humans. An infestation can be fatal if left untreated, but a doctor can usually treat myiasis by removing the larvae. People who work with livestock, have weakened immune systems, open wounds, or who sleep outdoors are most at risk for developing an infection, according to the CDC. But because screwworm is an insect and not a virus, it’s not contagious, Max Scott, a professor of entomology and plant pathology at North Carolina State University, told NPR.
The New World screwworm is endemic to South America and the Caribbean, and it isn't typically found in the U.S., according to the CDC. No cases of screwworm infestation have been found in U.S. animals so far. In the 1960s, the U.S. eradicated New World screwworms within the country by releasing male sterile screwworm flies into infested areas. The sterile flies mated with wild female flies, but the eggs didn't hatch, which caused screwworm populations to decline.
Since 2023, screwworm populations have been increasing in Central America and slowly spreading northward. In November 2024, a screwworm infestation in Mexico prompted the U.S. to temporarily pause livestock imports at the southern border. Imports resumed in January, only to halt again in May. Ports are now reopening in stages, according to the U.S. Department of Agriculture, and a new sterile fly dispersal facility is being constructed in southern Texas.
The New World screwworm is endemic to South America and the Caribbean, and it isn't typically found in the U.S., according to the CDC. No cases of screwworm infestation have been found in U.S. animals so far. In the 1960s, the U.S. eradicated New World screwworms within the country by releasing male sterile screwworm flies into infested areas. The sterile flies mated with wild female flies, but the eggs didn't hatch, which caused screwworm populations to decline.
Since 2023, screwworm populations have been increasing in Central America and slowly spreading northward. In November 2024, a screwworm infestation in Mexico prompted the U.S. to temporarily pause livestock imports at the southern border. Imports resumed in January, only to halt again in May. Ports are now reopening in stages, according to the U.S. Department of Agriculture, and a new sterile fly dispersal facility is being constructed in southern Texas.
CDC
https://www.cdc.gov/myiasis/about-new-world-screwworm-myiasis/index.html
About New World Screwworm Myiasis
Key points
- Myiasis is a parasitic infestation of fly larvae (maggots) in human tissue.
- New World screwworm (NWS) is a species of parasitic flies that can cause myiasis and feed on live tissue.
- It primarily affects livestock, but it can also infest people.
- NWS is typically found in South America and the Caribbean.
- You are at higher risk for NWS if you travel in these areas, are around livestock in rural areas where the flies are, and if you have an open wound.
Overview
New World screwworm (NWS) infestation occurs when NWS fly larvae (Cochliomyia hominivorax) infest the tissue or flesh of warm-blooded animals. In places where the flies are present, people can also become infested. Screwworm flies are attracted to and lay eggs on and in open wounds. NWS does not regularly occur or spread in the United States. The parasite is typically found in South America and the Caribbean. People who travel to these areas, spend time among livestock animals, sleep outdoors, and have an open wound are at greater risk of becoming infested with NWS.
Symptoms
NWS infestations are very painful. If you have an NWS infestation, you may see maggots (larvae) around or in an open wound. They could also be in your nose, eyes, or mouth. Tell your healthcare provider of any recent travel to Central or South America, or the Caribbean.
Symptoms can also include
- Unexplained skin lesions (wounds or sores) that do not heal.
- Skin wounds or sores that worsen over time.
- Painful skin wounds or sores.
- Bleeding from open sores.
- Feeling larvae movement within a skin wound or sore, nose, mouth, or eyes.
- Seeing maggots around or in open sores.
- A foul-smelling odor from the site of the infestation.
- Secondary bacterial infections sometimes occur and may cause fever or chills.
Keep Reading
Clinical Overview of New World Screwworm Myiasis
Risk factors
You may be at an increased risk for NWS if you travel to areas where the flies are present and
Have an open wound, from a scratch or cut, from an insect bite, or from a recent surgery.
Have a weakened immune system, for example from HIV, cancer treatment, or medications that weaken your immune system.
Have a medical condition that can cause bleeding or open sores, such as from skin or sinus cancer.
Sleep outdoors.
If you live, work, or spend an extended amount of time with (or near) livestock or other warm-blooded animals in these areas, you could also be at a higher risk for NWS.
How it spreads
New World screwworm infestations begin when a female fly lays eggs on open wounds or other parts of the body in live, warm-blooded animals. It primarily affects livestock but can also infest birds and people. The smell of a wound or an opening such as the nose, mouth, or eyes, umbilical cord of a newborn animal, or genitals, will attract the female flies. Wounds as small as a tick bite may attract a female fly to feed and lay her eggs. One female can lay 200 – 300 eggs at a time and may lay up to 3,000 eggs during her 10- to 30-day lifespan.
Eggs hatch into larvae (maggots) that burrow into the wound to feed on the living flesh. After feeding, larvae drop to the ground, burrow into the soil, and emerge as adult screwworm flies.
Prevention
Prevention is key to protecting yourself from myiasis. Prevent insect bites, especially when visiting tropical areas and spending time outdoors, and
Keep open wounds clean and covered.
Wear loose-fitting, long-sleeved shirts and pants, and socks to limit areas where you could get bitten.
Use an EPA-registered insect repellent.
Treat clothing and gear with products containing 0.5% permethrin.
Sleep indoors or in rooms with screens.
Treatment
If you see or feel maggots (larvae) in or on a wound or other area of your body, contact your healthcare provider immediately. They will need to remove the larvae, sometimes through surgery. Do not try to remove or dispose of the maggots yourself.
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