Maryland reports first US case of flesh-eating parasite in years

A Maryland resident contracted the New World screwworm after travelling from El Salvador. Photo / Getty Images

A human case of a flesh-eating parasite known as New World screwworm has been confirmed in a Maryland resident, the first in the United States in years, according to US and state health officials.

The case was confirmed on August 4 in a person who had travelled to the US from El Salvador, said Andrew Nixon, a spokesman for the Department of Health and Human Services.

The resident has recovered without evidence of infecting other humans or animals, state health officials said in a statement today.

A recent New World screwworm outbreak in Central America has raised concerns that it could spread to the US and devastate the cattle industry. State and federal health officials said the Maryland case is not cause for alarm.

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

Livestock are not at particular risk because of the Maryland case, the National Cattlemen’s Beef Association said.

“Based on what has been shared with state animal health officials, we do not see any elevated risk to the livestock industry at this time. We appreciate the diligence of human-health authorities,” the association’s chief executive, Colin Woodall, said in a statement.

The New World screwworm is a parasitic blowfly that feeds on the living tissue of warm-blooded animals and, in rare cases, humans – especially on open or untreated wounds.

As there is no existing treatment, “prevention and quick removal are key”, according to the Centres for Disease Control and Prevention.

HHS last week allowed the Food and Drug Administration to issue emergency use authorisations for drugs to treat or prevent screwworm in animals.

Screwworms have been largely eradicated in the US for the past 50 years, according to the FDA.

Recent outbreaks in both humans and animals across Central America and Mexico have pushed US authorities to ramp up efforts again.

Most US infections – including the latest Maryland case – are contracted through travel to tropical and subtropical regions, the CDC says.

Beth Thompson, South Dakota’s state veterinarian, told the Washington Post that the CDC last week had notified a group of state animal health officials and veterinarians about the case, which was first reported by Reuters.

About a week before the latest case was identified, the Agriculture Department announced sweeping plans to combat the pest, which Agriculture Secretary Brooke Rollins has vowed to eradicate.

In June, Rollins unveiled plans for an US$8.5 million ($14.5m) sterile fly production facility in South Texas, with the aim of dispersing sterile flies to stop the screwworms from reproducing.

“Our cattle ranchers and livestock producers are relying on the Trump Administration to defend their livelihoods,” Rollins said in a statement last week.

“Stopping this pest is a national security priority and we are linking arms across President Trump’s cabinet to defend our borders and push back this threat.”

The American Veterinary Medical Association urges veterinarians and livestock producers to look for signs of infestation, especially in animals that have recently given birth, have open wounds or have undergone surgery or procedures, such as dehorning or branding.

Some key signs include larvae visible in wounds or orifices, wounds with bloody discharge, an odour of decay, behavioural signs of irritation such as head shaking or rubbing against trees and signs of pain such as depression, irritability or isolating from other animals or people.

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