California Health Officials Urge Caution as Flesh-Eating Parasite Threatens to Spread

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California health authorities are raising red flags about a dangerous parasitic fly, known to feed on living tissue in both humans and animals. The New World screwworm, once eradicated from the United States, has recently been detected in southern Mexico and Central America — and now poses a potential threat to California.

A recent case involving a U.S. traveler returning from El Salvador has triggered heightened concern. The California Department of Public Health (CDPH) is warning that the parasite could enter the state either through infected travelers or animals, or by gradual migration northward from Mexico.

“This parasite poses a serious health risk if introduced into California,” the CDPH warned. “Early detection, rapid response, and public awareness are essential to prevent an outbreak.”

What Is the New World Screwworm?

The New World screwworm is a type of fly whose larvae (maggots) infest open wounds and feed on live flesh, causing a condition called myiasis. Once hatched, the larvae burrow into tissue, leading to intense pain, infection, and — in severe cases — tissue destruction or death if untreated.

The Centers for Disease Control and Prevention (CDC) describes the infestation as extremely painful, often marked by:

• Visible maggots in wounds, eyes, nose, or mouth

• Unhealing, foul-smelling sores

• Unexplained bleeding from open wounds

• Confusion or fever in advanced cases

In some regions affected by the parasite, more than 700 human infections and over 111,000 animal cases have been reported, along with several human deaths.

Who’s Most at Risk?

The risk is highest for individuals who:

• Have open wounds or skin ulcers

• Have compromised immune systems or chronic illnesses

• Sleep outdoors, particularly during the day (when the fly is active)

• Live or travel in areas with reported screwworm activity

Even small cuts or insect bites can be enough to attract the female fly, which can lay hundreds of eggs at once.

How to Protect Yourself

If you're in or traveling to an affected area, health officials strongly recommend the following precautions:

• Cover all open wounds with clean, protective dressings

• Use EPA-registered insect repellents on exposed skin

• Wear long sleeves, long pants, and socks to minimize skin exposure

• Treat clothing and gear with permethrin (0.5%) for added protection

• Sleep indoors, or if outdoors, use a screened tent or bed net

Keeping flies away from wounds is critical, as female screwworm flies are drawn to open sores to lay their eggs.

What to Do if You Suspect Infection

If you notice maggots or eggs on your body or in a wound:

• Seek medical help immediately

• Do not attempt to remove the larvae yourself

• Do not dispose of them in household trash — this could spread the infestation

• If any maggots fall out, place them in a sealed container with rubbing alcohol and take them to your healthcare provider

Doctors may need to surgically remove each maggot and treat the affected area to prevent further tissue damage or infection.

Ongoing Monitoring

As of now, there have been no confirmed cases in California livestock or wildlife, but public health officials remain on alert. Those returning from areas where the parasite is present — such as parts of Central America and southern Mexico — should monitor for symptoms and seek medical advice if they notice anything unusual.

The New World screwworm was officially eliminated from the U.S. in 1966, but its reemergence just south of the border — in areas within 70 miles of U.S. territory — has put health officials on high alert.