USDA to build US$750M sterile fly factory to combat screwworm threat

USA – The United States is investing US$750 million to build a new sterile fly production facility in southern Texas to stop the deadly New World Screwworm (NWS) from crossing the border and devastating livestock herds.

Announced by US Department of Agriculture (USDA) Secretary Brooke Rollins, the state-of-the-art factory will be constructed on an air base just 20 miles from Mexico. 

Once operational, within a year, the facility will churn out up to 300 million sterile screwworm flies per week, which will be released to overwhelm wild populations and prevent them from reproducing.

“This terrible pest is threatening American cattle production,” Rollins said. “We must construct an additional sterile fly production facility in the United States to stop the northward advancement.”

A border crisis for ranchers

The screwworm, eradicated from the US in 1966 after decades of intensive control, has been spreading rapidly through Central America and into Mexico. 

The USDA describes the parasite as a “devastating pest” capable of infesting livestock, pets, wildlife, and even humans. Female flies lay eggs in wounds, and once hatched, larvae burrow into living flesh, causing a condition called wound myiasis that can be fatal if untreated.

Although the parasite has not yet been detected in the US, Washington has already closed the border to imports of cattle, horses, and bison from Mexico. 

The move has worsened cattle shortages in the US, where the national herd is now at a 75-year low. Before the shutdown, Mexico supplied over one million feeder cattle annually into the US beef chain.

Ranchers in Texas vividly remember the last outbreak in the 1970s, which cost tens of millions to contain. 

“The smell is bad, and some of the wounds are horrific. You have humongous holes in these animals teeming with worms,” recalled Texas rancher Kip Dove, who witnessed infestations as a boy. “I don’t know if I could handle it if it happens now.”

A multi-pronged response

Alongside the new factory, USDA is investing US$100 million in enhanced surveillance and control measures, including new fly traps, lures, specially trained dogs, and “tick riders” patrolling the border on horseback. Outreach campaigns are also underway, with veterinarians and livestock owners receiving pest ID cards and alerts to spot early signs of infestation.

Global concern is rising. The World Organisation for Animal Health has warned that the reappearance of NWS in Central America is a “worrying development for animal health, human health, and biodiversity.” 

Belize recently confirmed its first human case, while Mexico continues to battle outbreaks in cattle and pets.

American Farm Bureau Federation President Zippy Duvall welcomed the investment as a proactive step. 

“Cattle markets are already volatile and the introduction of New World Screwworm within the US would only increase that volatility,” he said. “We thank USDA and Secretary Rollins for her leadership in protecting the domestic cattle industry and we stand ready to help ensure the speedy and efficient construction of this facility.”

Experts estimate that Texas alone could face US$1.8 billion in damages if screwworm gains a foothold. Despite the urgency, scientists warn that the US and Mexico must scale up sterile fly production dramatically; current facilities in Panama can produce just a fraction of the numbers needed.

“This might be the worst biological outbreak that we’re facing in our lifetime,” said Freddy Nieto, manager of El Sauz Ranch in South Texas. “We’ve faced the New World Screwworm before and succeeded. With collective action, we can do it again.”

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