Deadly flesh-eating parasite detected in US for the first time: emergency measures in place, symptoms explained

The first human case of the deadly flesh-eating parasite known as the New World screwworm has been detected in the United States, specifically in Maryland, in a person who recently returned from El Salvador. This parasitic fly lays eggs in wounds of warm-blooded animals. The larvae hatch and burrow into living flesh, feeding on it and causing serious tissue damage, which can be fatal if untreated. The infection is rare but extremely painful and dangerous. Emergency preventive measures are underway to contain any further spread and protect livestock and humans.


New World screwworm: a deadly flesh-eating parasite
The New World screwworm (Cochliomyia hominivorax) is a parasitic fly whose larvae invade open wounds and live flesh of warm-blooded animals, including cattle, wildlife, pets, and now humans. The female fly deposits eggs in wounds, and larvae burrow using sharp mandibles, feeding on living tissue for about a week before falling to the ground to mature. It was eradicated in the US decades ago but reemerged recently in Central America and Mexico, spreading northward toward the US border.


The US case and response

• The confirmed US case involves travel-related infection detected in Maryland, with diagnosis confirmed by larval image analysis.
• The individual is being treated, and the situation is under investigation by US Department of Health and Human Services, CDC, and Maryland health authorities .
• The risk to public health in the US is considered very low.
• The parasite reemerged near the Southern border, prompting a major emergency response including a multi-million dollar biosecurity plan led by USDA and state governments.
• Efforts include sterile fly production to halt reproduction, enhanced surveillance, and cross-border cooperation to prevent spread.
• An $850 million initiative in Texas aims to protect livestock by producing hundreds of billions of sterile flies weekly to disrupt parasite breeding.

Symptoms of screwworm infestation

• Screwworm larvae burrow into flesh, causing painful wounds.
• Wounds can become very inflamed, painful, and infected due to the larvae feeding on living tissue.
• If untreated, infestations can lead to severe tissue damage and death.
• Treatment involves laborious removal of larvae and thorough wound disinfection.
• Early intervention generally leads to survival, but delayed treatment is life-threatening.

Comparison to flesh-eating bacteria ( necrotizing fasciitis )

• Necrotizing fasciitis, caused by bacteria, has symptoms like intense pain around wounds, swelling, redness, fever, and rapid tissue damage.
• In contrast, screwworm infestation is caused by fly larvae physically eating living tissue.
• Both conditions cause very painful, spreading tissue damage and require urgent treatment.