Flesh-Eating Screwworms Found in U.S. Here’s What to Know

The HHS has confirmed a case of screwworms in a human in the U.S. (Bayu Murti ariwibowo | Dreamstime.com)

The first human case of the flesh-eating screwworm in decades has been confirmed in the U.S. in a person returning from a trip to Central America, according a report.

A screwworm is a parasitic fly that can be dangerous to humans, but is even more of a threat to cattle. Beef-producing giant JBS stock was edging up 0.4% just after the market opened.

The U.S. screwworm case is being investigated by the Maryland Department of Health and the U.S. Centers for Disease Control and Prevention, and was confirmed by the CDC as New World screwworm, HHS spokesman Andrew G. Nixon said, according to Reuters. It involves a patient who returned from El Salvador, he said.

Screwworms are a type of larvae which burrow into the flesh of a living being, eventually killing their host if left untreated. It can infest livestock, pets, wildlife and in rare cases, humans. The maggots’ feeding is comparable to a screw being driven into wood, giving the worms their name.

The pest was eradicated from the U.S. in the 1960s through an aggressive program of using radiation to sterilize male flies. However, agricultural officials are now increasingly vigilant as an outbreak has been traveling north from Central America and Mexico since 2023, risking harm to what is already the smallest U.S. cattle herd in more than 70 years. There’s a risk that it could create a shortage of beef, pushing prices higher.

The confirmation of a human case comes less than two weeks after Department for Agriculture Secretary Brooke Rollins traveled to Texas to announce a five-part plan to combat the pest.

“The risk to public health in the United States from this introduction is very low,” Nixon said.

The bigger concern is for cattle and other livestock. A USDA report from last year estimated that a screwworm outbreak in Texas, the largest cattle producing state, as much as $1.8 billion in livestock deaths, labor costs and medication costs.

The HHS and CDC were contacted for a comment outside of normal office hours on Monday and didn’t immediately respond.

Write to Elsa Ohlen at elsa.ohlen@barrons.com