U.S. Confirms First Travel-Associated Human Screwworm Case

The US Department of Health and Human Services (HHS) has reported the first human case in the United States of travel-associated New World screwworm, a flesh-eating parasite, from an outbreak-affected country, Cassandra Garrison, Tom Polansek, and Leah Douglas reported for Reuters.

The USDA has estimated that a screwworm outbreak could cost Texas about $1.8 billion in livestock deaths, labor costs, and medication expenses. (Photo: CSIRO Wikimedia Commons)

The case, investigated by the Maryland Department of Health and the US Centers for Disease Control and Prevention (CDC), was confirmed by the CDC on August 4 and involved a patient who returned from travel to El Salvador, HHS spokesman Andrew G. Nixon said in an email to Reuters.

Earlier, Reuters reported that beef industry sources said the CDC had confirmed a case of New World screwworm in a person in Maryland who had traveled from Guatemala.

Nixon did not address the discrepancy on the source of the human case.

“The risk to public health in the US from this introduction is very low,” he said.

Screwworms are parasitic flies whose females' lay eggs in wounds on warm-blooded animals. Once hatched, hundreds of screwworm larvae use sharp mouths to burrow through living flesh, eventually killing the host if untreated. The maggots’ feeding action resembles a screw being driven into wood, giving the pests their name.

The differing accounts from the US government and industry sources on the human case are likely to rattle cattle ranchers, beef producers, and livestock traders already threatened by screwworms moving northward from Central America and southern Mexico.

The confirmation of a human case comes just over a week after US Agriculture Secretary Brooke Rollins traveled to Texas to announce plans for a sterile fly facility as part of efforts to combat the pest.

The USDA has estimated a screwworm outbreak could cost Texas — the biggest US cattle-producing state — about $1.8 billion in livestock deaths, labor costs, and medication expenses, Heather Schlitz and Jarrett Renshaw also reported for Reuters.