Doctors across the United States are being advised to stay vigilant as the New World screwworm, a perilous and sometimes fatal parasite, edges closer to U.S. borders. The screwworm has recently been identified in Tamaulipas, a Mexican state situated just across the border from Texas. In response, the Centers for Disease Control and Prevention (CDC) has issued a health alert urging healthcare professionals and public health authorities to be on the lookout for any indications of the parasite’s presence.

The New World screwworm is notorious for its gruesome reproductive process. These flies lay their eggs in open wounds, as well as in the nose, ears, eyes, or mouth of their host. As the eggs hatch, the larvae, commonly known as maggots, begin their destructive journey by consuming the surrounding flesh as they burrow further into the host’s body.

Although livestock is the primary target of these parasites, any warm-blooded animal, including humans, can fall victim to their insidious infestation. If a screwworm infestation is not promptly addressed, it can prove fatal to humans.

The risk of encountering screwworms is notably higher for individuals who frequent areas where these flies are prevalent, such as parts of Central America and Mexico, especially if they have open wounds like cuts or scratches. Those who spend considerable time outdoors or in close proximity to animals are particularly at risk of exposure.

People are at the highest risk of being exposed to the screwworm if they spend time in areas where the flies are present, like Central America and Mexico, and if they have open wounds like scratches or cuts. Those who spend more time outdoors and around animals are at the highest risk of exposure.

What are the symptoms of the New World screwworm?

The CDC advises clinicians to consider the possibility of a screwworm infestation if they see any of the following signs:

• Visible larvae or egg masses, which might be wounds, ears, eyes, noses, mouths or another body orifice
• Destruction of healthy tissue
• People reporting a sensation of movement in a wound or orifice
• Foul odor, bloody discharge, swelling or pain around a wound or orifice
• Recent travel to areas where the screwworm is present, like Mexico and Central America

How is a screwworm infestation treated?

To treat a screwworm infestation, the CDC advises clinicians to remove all the eggs and larvae from the person’s body. That may require surgery if the maggots are deeply embedded.

The clinician should kill all larvae and eggs in a patient with a suspected case of New World screwworm. They should also check back in 24 to 48 hours to make sure all the larvae and eggs were eliminated.

There are no studies to prove any specific medication could be an effective treatment, says the CDC.

The agency says there are currently no known cases of New World screwworm in the U.S., but concerns recently grew higher as the parasite approached the U.S.-Mexico border. The recent outbreak has affected about 148,000 animals and 1,190 people in Central America and Mexico.