Flesh-eating insects found invading US through Mexican migrant route

An invasive species of flesh-eating flies has been discovered moving towards the US border, using the same route millions of migrants took to America in recent years.

The New World Screwworm (NWS) lays hundreds of larvae in the wounds of animals and people, which hatch within hours and start consuming the victim’s tissue.

These infestations can lead to deep, painful wounds that become infected and often result in death if left untreated.

Officials in Mexico have discovered several NWS cases in the country’s southern states of Chiapas, Oaxaca, and Veracruz – all of which were part of the migrant caravan route used by millions to cross the US border illegally over the last decade.

Researchers fear there may be no way of stopping the flies at the US-Mexico border and they’ll start infesting the South within two decades due to rising temperatures.

Research indicates states along the Gulf, including Texas, Florida, and Louisiana, are all at risk of seeing the parasites potentially killing cattle and people by 2055.

Although the threat of widespread outbreaks of NWS among people in the South, US shoppers would quickly feel the impact of this species killing local cattle.

Beef and dairy prices would likely rise because fewer cattle would mean less meat and milk available. Food shortages could occur, particularly for beef from Texas, which is home to 14 percent of all US cattle.

Screwworms first became a major problem for the US in the early 1900s, costing $200 million, roughly $1.8 billion today, in infected livestock, according to the University of Texas at Austin.

However, the species was wiped out in the US by 1982 using a clever method of sterilizing male flies using radioactive gamma rays so they couldn’t produce any offspring with the females.

The first human case of an NWS infestation was found in a 77-year-old woman from Chiapas in April. Health officials were able to stabilize her condition in time using antibiotics.

Another man in Chiapas was infested with NWS maggots in May after a dog bit him, creating an open wound. Mexico’s health ministry confirmed the case and said the 50-year-old was suffering from a fever, intense pain, and larvae visible in the wound. 

Experts in the US are worried it could have a devastating effect on the economy and local wildlife if it were to reach America.

‘It can have a huge impact, certainly an economic impact, because it decreases the health and wellness of our livestock,’ Texas Tech School of Veterinary Medicine Associate Professor Jennifer Koziol told Drovers in December. 

‘We’re thinking about loss of animal use, and certainly thinking about our wildlife populations that could be decimated by this disease,’ she added.

The New World Screwworm is also known as Cochliomyia hominivorax, or ‘man-eater.’ 

Female flies can lay up to 200 to 300 eggs at once and up to 3,000 in their lifetime. Infestations can also be visible on the skin.

The parasite hasn’t been seen in the US in more than 40 years after extensive federal and state sterilization efforts managed to eradicate the fly in North America.

However, the species still existed in South America and eventually broke through a containment barrier at the Darién Gap in Panama in 2022.

This area is the same region connecting North and South America that over 1.2 million migrants crossed through between 2021 and 2024, according to Panama’s National Migration Service.

The Darién was also an area noted for its high injury rates and health risks among the massive caravans attempting to reach the US through Mexico, creating a potential breeding ground for NWS cases.

After breaking back into Mexico in 2022, sterile flies were once again used to keep the infestations down, but cases continued to be reported moving north towards the US.

By June 2024, the man-eaters were found in cows in Chiapas, near the Guatemala border.

This month, the flies have now been found in areas just 500 miles from the southern border.

According to a 2019 study in Medical and Veterinary Entomology, at least five US states are projected to be infested with screwworms again by 2055.

This includes Texas, Florida, Louisiana, Arizona, and California. The main cause is feared to be climate change, as this species thrives in warmer temperatures.

In May, US officials officially suspended imports of live cattle, horses, and bison from Mexico after NWS cases were found moving north, getting within 500 miles of the southern border.

So far, there haven’t been any cases of the screwworms making it into the US this year, but their ability to live within wildlife, livestock, pets, and people has added another level of concern for border officials.

On May 27, US Secretary of Agriculture Brooke Rollins announced a $21 million partnership with the Mexican government that the countries hope will eradicate the insects before they can spread further north.

The money will go towards updating a fruit fly sterilization facility in Metapa, Mexico. The lab will attempt to sterilize 60 to 100 million male NWS flies every week using radiation and then release them into Mexico.

When these irradiated flies mate with the larvae-carrying females, the insects won’t be able to produce any offspring.

That should reduce the fly’s population over time, lowering the chances of infecting more animals and people throughout North America.

‘The investment… is one of many efforts my team is making around the clock to protect our animals, our farm economy, and the security of our nation’s food supply,’ Secretary Rollins said in a statement.

Despite the ongoing sterilization effort, experts have warned that the clock is ticking for US and Mexican officials to stop the spread.

Phillip Kaufman, a professor of entomology at Texas A&M University, said: ‘Producing sufficient numbers of sterile flies and getting them released in the correct places and at the right time is critical.’

‘If the flies move further north than the isthmus in southern Mexico, it becomes more and more challenging to contain them,’ the professor told Newsweek.