For Clinicians | New World Screwworm in Humans

Oct 27, 2026 | Educational Series, HCP

couple looking at computer asking questions

For Clinicians | New World Screwworm in Humans: The Wound Check, the Larvae, and the Risk

By Dr. Jamie Wilkey, PharmD, Director of Clinical Education
Medically reviewed and edited by Kristen Carpenter, PA-C

New World screwworm is the latest health headline. This one came from an elk in Texas. On October 21, USDA confirmed the parasite in an elk on a Pecos County game ranch, the first US wildlife case of this outbreak¹. We don’t ride the hype wagon that turns every news story into a healthcare emergency, and CDC still rates the risk to the US public as very low². But when our clinical team reviewed the cases, we were kind of struck by who this has actually reached. The people who’ve gotten it look a lot like the patients we serve at Jase.

Fair warning: this article isn’t for the squeamish. We’re talking about maggots in wounds. You’re clinicians, so we know you can handle it.

Today we’re covering who’s actually at risk for screwworms in the US, what an infested wound looks like, what to do with the larvae, and what antibiotics can and can’t do.

Can people in the US get New World screwworm?

Yes, but only in one very specific and super gross way. A female fly lays her eggs on an open wound or a mucous membrane, and the larvae hatch and burrow in to feed on living flesh³. Most maggots you’ve seen in a wound stay up on the surface. These go deep deep deep, which is the problem.

The fly is the only route. Screwworm doesn’t pass from person to person, and nobody catches it from an infested animal⁴. So the clinical question is narrow: does this patient have an open wound somewhere the flies are? Right now that means parts of Texas and New Mexico, plus travel to Mexico or Central America. And CDC means any open wound, even a scratch, an insect bite, or a recent surgical site³.

That elk that is all over the headlines these days is why we’re writing now. Wildlife is harder to track and control than cattle, and CDC listed wildlife detection as one of the developments that would change its risk assessment⁴. Whether cold weather holds the fly back this winter is still an open question.

Screwworm finds older patients with chronic wounds

Clinicians, you won’t be surprised that most of these infestations are on the legs and feet. If something is eating a patient’s foot and they don’t know it, our brains go straight to the likely reasons. They probably can’t feel it because of diabetic neuropathy, or they have a hard time reaching or seeing that part of their body. A heel or the back of a calf is easy to miss when bending over is hard, and a diabetic foot ulcer or a venous stasis ulcer can stay open for months. That gives the fly both things it needs: an open wound and time.

The people actually at risk look exactly like that. In Mexico’s 202 confirmed human cases between April 2025 and March 2026, the average patient was 61, most had at least one chronic condition (diabetes was the most common), and more than half of the infestations were on the legs or feet⁵. CDC describes the same group: older adults and people with limited mobility, whose infestations can go unnoticed until treatment is late⁴. The deaths in the Mexico series happened in even older patients, and the authors attributed only one of the six directly to the larvae⁵.

These patients aren’t necessarily frail, either. Plenty of them still work cattle, hunt every fall, or spend the winter in South Texas, and they just don’t notice a wound on a foot they can’t feel. In the office, that means taking the sock off and looking at the feet of your patients with diabetes who live in or travel to these areas. At the pharmacy counter, it means asking a few questions when someone buys dressings for a foot or leg wound that won’t heal and has started to smell.

What does an infested wound look like, and what do you do with the larvae?

You’ll probably smell it before you see it. Texas health officials describe a very painful, foul-smelling wound with visible larvae, sometimes with an egg mass in or around the wound or a body opening, and often more tissue damage underneath than the surface suggests⁶. When a wound like that shows up in a patient who lives in, works in, or recently traveled through an area with the fly, screwworm belongs on your list.

The protocol from there is short:

Remove every larva. They burrow deep, so the ones you can see are not all of them, and getting the rest out may take surgical debridement⁶.
Collect larvae from different depths of the wound and drop them into a leak-proof container with enough 70% ethanol to cover them⁶.
Never throw live larvae in the trash or on the ground. Kill them in the alcohol, then dispose of the sealed container as medical waste, because a live larva in the dumpster is how the fly gets a new foothold⁶.
Recheck the wound in 24 to 48 hours to make sure nothing in there is still alive⁶.
Call your local or state health department right away. Texas treats a suspected case as immediately reportable, and the health department will help get the larvae identified⁶. Reporting rules vary by state, so check yours.

For patients with open wounds, your front desk or MA can add one intake question: have you been in Texas, New Mexico, Mexico, or Central America recently? At the pharmacy counter, send the patient to be seen that same day and tell them not to pick the maggots out at home. CDC says patients shouldn’t try, since getting every larva out can take a clinician and sometimes surgery².

What can antibiotics do for screwworm?

Antibiotics do less here than patients will hope. Larvae aren’t bacteria, so an antibiotic does nothing to the infestation itself. What it can treat is a secondary bacterial infection in a wound that’s been chewed open, and Texas health officials remind clinicians that it may need antibiotic therapy⁶. That call follows the same logic as any other infected wound, starting with whether you’re looking at a purulent pocket or a spreading cellulitis.

Nothing treats the larvae themselves. CDC says no licensed human vaccine or medication currently prevents or treats screwworm in people⁴. The treatment with evidence behind it is the protocol above: get every larva out and keep caring for the wound.

Your patients may have read otherwise, because there are plenty of guesses online that whatever works on cattle will work on people. Don’t follow treatment advice that comes only from social media or forums. Stick with what the medical literature has shown to be safe and effective in humans. For screwworm, that’s still a clinician with nerves of steel and a pair of tweezers.

The bottom line: the wound nobody’s checking

Right now, care for a wound like this is all or nothing. Either a clinician sees it, or the patient is alone with a sore on a foot they can’t feel. The step in between is counseling. Tell your patients in fly areas to wash open wounds with soap and running water, keep every wound covered, even a tiny scratch or a bug bite², check their feet and legs every day, and get seen the same day if they ever see or feel maggots.

For patients who spend long days outside, like hunters, ranchers, and anyone working cattle, add the fly side of it. CDC recommends loose-fitting long sleeves and pants, a hat, and socks, clothing and gear treated with a 0.5% permethrin product (the kind made for fabric, not skin), an EPA-registered insect repellent, and sleeping indoors or somewhere screened². Fall hunting season is a good time to bring it up.

That’s appropriate medical preparation, with no prescription anywhere in it. It complements the primary care you’re already giving, and it covers the stretch between visits when nobody else is looking at that foot.

The health risk to the US public is very low, and the patients who are actually at risk are a narrow group you already know. The protocol is short, and no drug treats the larvae. We’ll keep publishing how we think through headlines like this one, so you have a clear clinical picture to point to when your patients bring them in or pepper you with questions from what they’re reading.