What is the New World Screwworm Fly? Know How US Plans to Fight It

The New World screwworm fly had been eradicated for decades because it was a significant threat to livestock, pets, and even humans. But, they are making a comeback as per the latest reports. This infamous flesh-eating parasite is now encroaching on the US border. The fly is a small yet powerful insect that was once a major concern for ranchers. Not just that, it is necessitating a renewed and urgent battle, as the US implements assertive strategies to prevent its re-establishment and protect the nation's animals and food supply.

Check Out: Seasons of the Year in the United States: What Season is It in the US Now?

What Exactly is the New World Screwworm Fly?

The larvae of the metallic blue blow fly known as the New World screwworm fly (Cochliomyia hominivorax) are obligatory parasites. Screwworm larvae burrow into and eat the living flesh of warm-blooded animals, such as cattle, horses, bison, deer, pets, and humans (rarely), in contrast to most maggots that feed on dead tissue.

But female flies are attracted to open wounds as small as tick bites. So that they can lay hundreds of eggs there. Once hatched, the larvae resemble screws as they tunnel deeper, which can cause severe pain, extensive tissue damage, and potentially death if untreated.

Check Out: US Entry Tips for International Students: What Harvard's Advisory Means and How to Prepare in 2025

Why is the New World Screwworm a Concern Now?

The New World screwworm was successfully eliminated from the US and Mexico for many years. It was primarily held in check by a sterile insect technique (SIT) barrier situated in Panama. However, since 2022, there's been a clear increase in incidents throughout Central America, and the fly has advanced deeper into southern Mexico. It is now closer to the U.S. border than at any point before. This northward movement poses a significant threat for several reasons. 

• This northern progression presents a considerable danger due to several factors.  

• It possesses the potential to inflict severe damage upon the multi-billion-dollar US livestock industry.

• There are chances of infestations that can further lead to immense suffering and death for affected animals.

• Although it is uncommon but human infestations are a possibility too. Especially for those who are more susceptible.

  Taking action against New World Screwworm 💪@SecRollins launched a new sterile fly dispersal facility in South Texas this morning and announced a five-pronged strategy to enhance USDA's ability to combat this pest and protect the nation.
  
  🔗https://t.co/6MarsCCcCH pic.twitter.com/yVdqqu9uFJ

  — Dept. of Agriculture (@USDA) June 18, 2025

How Did the US Eradicate the Screwworm Before, and What's the Plan Now?

So, how did the U.S. beat the screwworm before? They used the Sterile Insect Technique. Billions of male flies were mass-bred, made sterile with radiation, then released from planes. Since female flies only mate once, mating with a sterile male meant no offspring, causing the population to crash.

The USDA is retaliating today. Livestock are no longer allowed to cross the US-Mexico border. Additionally, they are planning a new release facility in Texas and investing $21 million to increase sterile fly production in Mexico. To keep everyone vigilant, they are also increasing surveillance and public awareness initiatives.