New World Screwworm Discovered For The First Time In The US: Is An Outbreak Of 'Human-Eating' Parasite Imminent?

A confirmed case of New World screwworm (NWS) myiasis has been reported in Maryland, raising fresh concern about whether the parasite could re-establish itself in the United States. The fly, notorious for feeding on living tissue, has long provoked lurid headlines and widespread public alarm.

Experts, however, stress that while the parasite can cause serious infections, the threat to human health remains very low. Scientific evidence and the history of eradication programmes suggest the likelihood of a widespread outbreak is limited, especially with existing controls in place.

What the Latest Case Shows

The rare case was identified in a Maryland patient who had recently returned from Guatemala, according to Reuters. It is the first human instance recorded in the US this year.

The US Animal and Plant Health Inspection Service (APHIS) confirmed that NWS was eradicated domestically in 1966, though it remains present in parts of Central and South America. Human cases, while distressing, are rarely fatal and can be treated effectively if diagnosed early and managed appropriately.

Why Screwworms Are Called 'Human-Eating'

The New World screwworm fly (Cochliomyia hominivorax) has earned its grim nickname by laying eggs in open wounds of warm-blooded animals. The larvae burrow into healthy tissue, causing painful and potentially severe infections.

To combat the parasite, the US previously used the sterile insect technique, releasing sterilised male flies to break the breeding cycle. That programme successfully eliminated the screwworm in the country and became a model for pest control internationally.

With the new case confirmed, the US Department of Agriculture (USDA) has announced a $750 million (£590 million) action plan. Measures include constructing a sterile fly production facility in South Texas, deploying detector dogs and 'Tick Riders' to monitor livestock, and approving emergency-use medicines for animals.

Economic Risks and Official Response

Beyond public health, screwworms present a significant threat to agriculture. An uncontrolled outbreak could cause losses of up to $1.8 billion (£1.4 billion) in Texas alone. Wider disruptions to cattle farming and beef exports could increase food costs across the country, according to the Grand Pinnacle Tribune.

Policymakers have called for stronger border safeguards, enhanced surveillance and quicker response systems to prevent the parasite from spreading. Public information campaigns are also being reinforced to encourage the early reporting of suspected animal infections.

Although the confirmed case has heightened awareness, experts note that existing detection and control systems are specifically designed to prevent escalation. For comparison, the UK has never recorded a human case, though public health agencies continue to monitor risks linked to international travel and imported livestock.

The Outlook

The Maryland case illustrates that New World screwworm remains a risk for travellers returning from endemic regions. However, health authorities say it does not represent a public health emergency. With containment protocols already in place and long-term control infrastructure being expanded, the prospect of a full outbreak is considered low.

Specialists argue that vigilance, swift reporting and international cooperation remain essential to ensuring the parasite does not regain a foothold. While the insect's grisly reputation attracts sensational headlines, the scientific consensus is that an outbreak of this so-called 'human-eating' parasite is not imminent.