AS the New World Screwworm Fly outbreak spreads north across Mexico closer to the United States border, the US is mounting major control measures including the use of a biological control agent.

A release issued last week by the US Department of Agriculture graphically illustrates how seriously the US is taking the parasite threat, at a time when Australia faces its own exotic disease risk through Lumpy Skin Disease, carried by midges.

A cowboy herding cattle on a ranch in eastern Oregon. Picture: Shutterstock

New World Screwworm has been detected only 110km from the Mexican/US border, and the Texas Animal Health Commission remains in high-alert surveillance mode.

Mexico only reported the fly for the first time in 2024.

The US military has been enlisted to help construct an enormous sterile fly production facility at Moore Air Base in Edinburg, Texas, at an estimated cost of up to A$140 million.

The facility will produce hundreds of millions of sterile screwworm flies each week for release along the US/Mexican border, to try to stem the advance.

The USDA release said the new production facility was projected to begin production in November 2027, with an initial goal of producing 100 million sterile flies weekly, before scaling up to 300 million/week.

The release also carried an update on renovations to an existing sterile fruit fly facility in Metapa, Mexico, which will double Mexico’s sterile fly production capacity once it is complete. The expanded Mexican facility will produce both sterile fruit flies and sterile screwworm flies.

USDA invested the equivalent of A$29 million and is providing technical expertise to support the Mexican project, with production expected to begin around mid-year.

The US Army Corps of Engineers will design, engineer and build (along with a commercial contractor) the new Texas sterile fly facility. The facility is one of five components in USDA’s strategy to fight New World Screwworm, expanding the US domestic response capacity, bolstering protection for US livestock, wildlife and public health, the release said.

“The Army Corps of Engineers is an essential partner in quickly bringing this facility to life and further highlights the Trump Administration’s government wide effort to fight the New World Screwworm threat in Mexico,” US Secretary of Agriculture Brooke Rollins said in the statement.

“The Army Corps is the best in the business and their engineering expertise and proven track record in delivering complex projects will help ensure we can build a modern, resilient facility that protects American agriculture from invasive pests for decades to come. This first-of-its-kind facility on US soil will ensure we are not reliant on other countries for sterile flies.”

How do sterile flies work?

A sterile fly production facility is a specialised bio-secure complex where New World Screwworm flies are bred, raised and sterilised using irradiation and then released into targeted areas.

Female Screwworm flies only mate once in their lives, so if they mate with a sterile male, they lay unfertilised eggs that don’t hatch.

This method, known as the Sterile Insect Technique, has been a cornerstone of proven screwworm eradication efforts for decades and is recognised worldwide as an effective, environmentally responsible approach to insect control.

Sterile Insect Technique, when paired with surveillance, animal movement restrictions, and education and outreach, is a proven and effective tool for controlling and eradicating New World Screwworm, the USDA statement said.

USDA currently produces 100 million sterile flies weekly at another facility in Panama, dispersing them within and just north of affected areas in Mexico. The expanded fly breeding facility in Mexico, subsidised by the US, will double that capacity.

The new facility at Moore Air Base in Texas will be the only US-based sterile fly production facility and will work in tandem with the others in Panama and Mexico to help eradicate the pest and protect American agriculture, the release said.

About New World Screwworm

The New World Screwworm is a parasitic fly whose larvae feed on warm blooded animals, causing severe animal health impacts and significant economic losses if not controlled. The fly is now endemic across most of South America and the Caribbean, and has more recently re-emerged across Central America, arriving in Mexico in 2024.

The US eliminated the pest in 1966 and has maintained that freedom through the ongoing sterile fly program and international partnerships. Mexico also managed to eradicate an earlier infestation in 1991.