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The first case in the United States of a deadly flesh-eating screwworm parasite has been detected. A person in Maryland was treated for the parasite after travelling from Guatemala, which follows an outbreak among animals that began in Central America and southern Mexico at the end of last year.

The parasitic flies burrow into the flesh of cattle and other warm blooded animals while they're alive, and can be fatal if left untreated. Beth Thompson, South Dakota's state veterinarian, said on Sunday that she was informed of the first US case last week, with a Maryland state government official also confirming the case. The individual has now been treated, with numerous prevention measures implemented, Reuters reports.

"This is the first human case of travel-associated New World screwworm myiasis (parasitic infestation of fly larvae) from an outbreak-affected country identified in the US," HHS spokesperson Andrew Nixon said in an emailed statement, according to Reuters.

The parasite can be deadly among cattle and wildlife, which has previously infected humans outside of the US.

The female screwworm fly lays eggs in open wounds of animals which will then hatch. The screwworm larvae use their razor-sharp mouth to burrow through living flesh.

While animals and humans are able to survive if cases are detected early enough, treatment for the parasite involves removing hundreds of hatched screwworm larvae.

The Centers for Disease Control and Prevention (CDC) said: "Infestations are very painful. If you have a new world screwworm (NWS) infestation, you may see maggots around or in an open wound. They could also be in your nose, eyes, or mouth."

Despite the parasite being eradicated completely from North America decades ago, infestation in cattle has surged in South America over the past few years.

In 2023, cases in Panama surged, with subsequent outbreaks reported the following year in Costa Rica, Nicaragua, Honduras, Guatemala, Belize, El Salvador, and Mexico.

Earlier this year, the US suspended imports of livestock, including cattle and horses, across the border with Mexico due to the spread of the parasite towards the country.

The US agriculture secretary has pledged to repeatedly keep screwworm out of the country, having recently travelled to Texas to announce plans to build a sterile fly facility there in a bid to combat the parasite.

The facility produces a large quantity of male flies and sterilises them in a bid to collapse the population over time.