The US eradicated this flesh-eating parasite decades ago. Now it is detected in Texas and New Mexico

For decades, the United States had largely consigned one of its most disturbing agricultural threats to history. The New World screwworm, a parasitic fly whose larvae feed on the flesh of living animals, was eradicated from the country in 1966. Now, the pest has returned, with detections in Texas and New Mexico raising fresh concerns about livestock, wildlife, pets and, in rare cases, humans. Researchers at the University of California San Diego have developed a new tracking system to help officials determine where the parasite could appear next.

The threat is unusual because the insect itself is not what causes the most damage. It is the larvae that emerge after female flies lay eggs in wounds or natural openings on warm-blooded animals. Once they hatch, the larvae burrow into living tissue and feed, causing wounds to become deeper and potentially leading to severe infections.

Why The Flesh-Eating Parasite Is So Dangerous

Unlike ordinary maggots, which generally feed on dead or decaying material, New World screwworm larvae consume living flesh. An infestation can therefore become progressively more damaging as the larvae continue feeding inside a wound. Livestock can suffer serious injuries, while wildlife and pets can also be affected. Human infections are uncommon, but people can also develop screwworm myiasis if larvae enter wounds or mucous membranes.

ID 134271385 Reuters 1200 X 900


Also Read: Ohio-based company transforms old wind turbine blades into beautiful, sustainable benches, tables and other public-space furniture

The United States has experienced the consequences before. According to the US Department of Agriculture's Animal and Plant Health Inspection Service (USDA APHIS), New World screwworm was eradicated from the country in 1966 using the Sterile Insect Technique. A smaller outbreak in the Florida Keys was also eliminated in 2017. USDA says the pest has since moved north through Central America and Mexico, increasing pressure on the US to prevent another sustained outbreak.

The US Has Already Seen What This Pest Can Do

The parasite was once a major economic problem for American farmers. ScienceDaily's report, based on research from UC San Diego, notes that New World screwworm caused estimated losses of $50 million to $100 million every year in the Southwest during the 1950s before eradication efforts pushed it out of the country.

USDA records show just how valuable eliminating the pest became. An APHIS historical assessment estimated that remaining free of New World screwworm produced major benefits for American livestock producers through fewer animal deaths, lower veterinary and treatment costs and improved meat and milk production. The concern now is that the old threat is appearing in places where officials had hoped it would never return.

Also Read: Georgia engineers transform a 7,000-pound old wind turbine blade into a pedestrian bridge in Atlanta and also made bicycle shelters and playground equipments

Scientists Are Building A Map Of Where It Could Strike Next

Researchers from UC San Diego and the County of San Diego Health and Human Services Agency have developed a dashboard that combines confirmed detections, environmental conditions and even news reports to estimate screwworm risk at the county level. The unusual addition of media reports could help officials detect warning signs before traditional surveillance systems catch up.

Seema Shah, medical director of the San Diego County Public Health Services Department's Epidemiology and Immunisation Services Branch, explained that "traditional reporting mechanisms for public health are often delayed." She said incorporating media reports could help identify potential threats sooner. The dashboard is currently restricted to public health officials and project partners, although researchers hope a public version will eventually be available.

Also Read: Tennessee turned 100 tonnes of old wind turbine blades into material for new products for automobiles, boats and construction

The US Is Bringing Back An Old Weapon

The most important weapon in the fight is not a conventional pesticide. It is another fly. Under the Sterile Insect Technique, huge numbers of male screwworm flies are raised and sterilised, usually through irradiation, before being released into affected areas. Female screwworm flies mate only once, so when they mate with sterile males, they produce eggs that cannot develop into viable offspring. Releasing enough sterile males can therefore drive the wild population down.

The method has already worked once. USDA says its sterile-insect programme helped eradicate New World screwworm from the US in 1966 and remains a cornerstone of the current response. The department is now expanding production capacity, with a planned Texas facility expected to produce up to 300 million sterile flies per week. USDA is also developing newer approaches. Its NovoFly strain is designed to produce only males, potentially increasing the number of useful sterile flies available for release.

Also Read: Florida dumped 500,000 tonnes of used oyster shells into the Gulf. What happened next surprised researchers in development of new reefs, and cleaner water

Why Officials Are Watching The Situation Closely

The return of New World screwworm is not simply an agricultural problem. Because the parasite can affect livestock, wildlife and pets, controlling it requires coordination between veterinarians, farmers, wildlife specialists and public-health agencies. USDA has already confirmed a case in a Texas calf and established surveillance, movement controls and targeted sterile-fly releases in response.

The department says its wider goal is to prevent the parasite from becoming established again in the United States. For now, scientists are trying to stay ahead of the pest rather than wait for it to spread. A parasite that the US successfully eliminated more than half a century ago has returned but this time, researchers have decades of experience, new tracking technology and a proven biological weapon on their side.