Tourist infected with flesh-eating New World screwworm after El Salvador holiday

An American tourist has been diagnosed with a rare flesh-eating parasite after visiting El Salvador.

The case, investigated by the Maryland Department of Health and the US Centers for Disease Control and Prevention(CDC), was confirmed as New World screwworm on August 4. It is the first reported US case tied to travel to a country with a current outbreak.

The patient, from Maryland, was diagnosed after returning from the country in Central America. Federal health officials acknowledged the infection in an emailed statement Monday, but did not describe the patient's condition. They collaborated with Maryland health officials, the statement said.

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New World screwworm is a fly that lays its eggs in open wounds and body opening such as the eyes, ears, nose or mouth. It primarily affects livestock and is rare in humans. It does not spread from person to person, and poses a very low risk to the public, according to US health officials.

The smell from a wound or opening such as the nose, mouth, eyes, genitals or umbilical cord of a newborn animal can attract the female flies. The females can be attracted from a wound as small as a tick bite, with one female able to lay 200-300 eggs at a time and capable of laying up to 3,000 eggs during her 10-30 day lifespan.

The eggs then hatch into larvae, or maggots, which then burrow into the wound to feed on the living flesh. After they are done feeding, the larvae drop to the ground where they burrow in the soil and emerge as adult screwworm flies.

The parasite has been a larger concern to ranchers, as cattle infestations have been moving northward through Central America and Mexico. The CDC is working with the US Agriculture Department to prevent further spread, officials said.

The pest was a problem for the American cattle industry for decades until the US largely eradicated it in the 1970s. The parasite is not widespread in the US and is typically found in South America and the Caribbean, according to the CDC.

People who travel to these areas, spend time among livestock animals, sleep outdoors, and have an open wound are at greater risk of becoming infested with NWS, the website adds. If you are infected, you may see maggots around or in an open wound.

The main symptoms including unexplained skin lesions that don't heal, skin wounds or sores that worsen over time, painful skin wounds or sores and bleeding from open sores. Infected people may also feel larvae movement within a skin wound or sore, nose, mouth, or eyes, or pot maggots around or in open sores.

A foul-smelling odour could also be felt from the site of the infestation, the CDC adds. There is also a risk of secondary bacterial infections which may cause fever or chills. Protection is key to protect yourself from the infection - when visiting affected countries you should aim to prevent insect bites by using repellent, keep open wounds clean and covered, wear loose-fitting clothes, and sleep indoors or in rooms with screen.

If an infestation occurs, you should seek immediate medical help as doctors will need to remove the larvae, sometimes through surgery. You shouldn't try to remove or dispose of the maggots yourself, the CDC says.