Warning issued as first case of travel-associated flesh-eating parasite confirmed in the US

The Centers for Disease Control and Prevention has shared insights to a flesh-eating parasite which are key to be aware of as the US confirmed its first case in a human in Maryland.

Known as the New World screwworm (NWS), the creature is a species of parasitic fly that feeds on live tissue, and can cause a parasitic infestation of maggots in human tissue – a scenario known as myiasis.

The Department of Health and Human Services (HHS) announced the first human case of the parasite in the US on Monday (August 25), explaining that it had been identified in a person who had recently traveled to El Salvador.

The announcement came after the parasite was confirmed to be screwworm by the Centers for Disease Control and Prevention and the Maryland Health Department on August 4.

The CDC confirmed the case before it was announced to the public

What is the human case of New World screwworm?

While the parasite primarily affects livestock, it can also infest people. HHS spokesperson Emily G. Hilliard announced in a statement that the case confirmed on August 4 was ‘the first human case of travel-associated New World screwworm myiasis’.

Hilliard added that the parasite came from an ‘outbreak-affected country’, however the Maryland Health Department assured the patient had since recovered from the infection.

An investigation has also confirmed that there is ‘no indication of transmission to any other individuals or animals’.

How is New World screwworm spread?

Though authorities have not identified any evidence of a spread among humans, the CDC has explained that the parasite can be passed when NWS fly larvae infest the tissue or flesh of warm-blooded animals, including humans in places where the flies are present.

Screwworm flies are typically attracted to open wounds, where the female may lay its eggs.

The eggs then hatch into larvae – aka maggots – which can burrow into the wound and feed on the flesh.

Screwworm infestations cause maggots in open wounds

Who is most at risk of New World screwworm?

The CDC has assured that NWS does not regularly occur or spread in the United States, and instead the parasite is typically found in South America and the Caribbean.

When announcing the case in the US, the HHS said: “The risk to public health in the United States from this introduction is very low.”

However, there are certain circumstances that may put people more at risk, including travelling to locations where the parasite can be found, and spending time among livestock animals.

Sleeping outdoors, having an open wound and having a weakened immune system may also increase the risks of an infestation of the parasite.

What are the symptoms of New World screwworm myiasis?

The CDC has warned that NWS infestations are very painful, and you may recognize it if you have maggots in or around an open wound. If you have an infestation, you should contact your healthcare provider immediately.

Other symptoms of an infestation can include:

Unexplained skin lesions (wounds or sores) that do not heal.

Skin wounds or sores that worsen over time.

Painful skin wounds or sores.

Bleeding from open sores.

Feeling larvae movement within a skin wound or sore, nose, mouth, or eyes.

Seeing maggots around or in open sores.

A foul-smelling odor from the site of the infestation.

Secondary bacterial infections sometimes occur and may cause fever or chills.

Screwworm can kill livestock

While there is no evidence of a human outbreak, the parasite can also devastate cattle herds, destroy wildlife and kill pets.

To help tackle an outbreak, Agriculture Secretary Brooke L. Rollins has announced a five-part plan which involves breeding sterile flies and releasing them over southern Texas and Mexico to try and prevent a spread of the parasite.