US Deploys Billions of Sterile Flies to Halt Flesh-Eating Pest Invasion from Mexico
US Deploys Billions of Sterile Flies to Combat Flesh-Eating Parasite Near Mexico Border
The U.S. is launching a massive effort to stop the New World Screwworm, a deadly flesh-eating parasite, from crossing into the country. After being eradicated in the U.S. over 40 years ago, the pest resurfaced in Mexico in late 2024, prompting urgent action led by the USDA.
The Threat: A “Man-Eater” Parasite
The New World Screwworm (Cochliomyia hominivorax)—whose name means “man-eater”—lays eggs in open wounds of animals. The larvae burrow into flesh, causing severe tissue damage. Left untreated, infections kill livestock within two weeks. Female flies can lay 300 eggs at once, producing over 3,000 in their lifetime. Infections manifest as wriggling maggots on the skin, leading to fatal wounds.
[Image: Close-up of New World Screwworm larvae infesting a cow’s wound. Caption: The parasite’s larvae resemble tiny, white screws and can kill livestock in days.]
The Plan: Sterile Insect Technique (SIT)
Using the proven Sterile Insect Technique, scientists will breed male screwworm flies, sterilize them via radiation, and release them by plane across southern Mexico and Texas. These sterile males mate with wild females, producing infertile eggs and reducing populations over time.
“It’s a science-based solution to a major problem,” said Edwin Burgess, a University of Florida parasitologist. The method, first tested in the 1950s, eradicated U.S. screwworms by the 1970s without pesticides.
Scaling Up Production
A Panama facility currently breeds 117 million flies weekly. New plants in Texas (opening late 2025) and Metapa, Mexico (July 2026) aim to boost output to 400 million flies per week. The USDA is investing $8.5 million in Texas and $21 million in Mexico to convert facilities for mass production.
[Image: Workers handling containers of fly pupae in Panama. Caption: Facilities in Panama and soon Texas/Mexico will produce billions of sterile flies.]
Risks and Challenges
While SIT is eco-friendly and targeted, risks remain. A 2024 plane crash during a fly-release mission in Guatemala killed three, underscoring logistical dangers. Breeding the flies also requires precise conditions: larvae need nutrient-rich diets of cattle blood plasma and egg powder, while adults demand specific cues to lay eggs.
Economic and Food Security Stakes
Texas, home to 14% of U.S. cattle, faces severe risks. An unchecked infestation could devastate herds, spike beef/dairy prices, and disrupt food supplies. The USDA warns losses would ripple through agriculture, calling the parasite a “serious threat.”
[Image: Cattle grazing in Texas. Caption: Texas’ massive cattle industry is at risk if the screwworm spreads.]
Migration Routes and Climate Change
The parasite’s spread is linked to migration through Panama’s Darién Gap, where over 1.2 million migrants traversed recently, possibly carrying infected livestock. As of mid-2024, screwworms were detected just 500 miles from the U.S. border. Climate change may worsen the threat, with models predicting the pest could infest southern states year-round by 2055.
Long-Term Vigilance Needed
Despite past success, experts stress ongoing vigilance. “Victories can be undone,” Burgess cautioned. The USDA allocated $165 million for emergency measures, including surveillance and quarantine systems. Future facilities may need to operate indefinitely to prevent resurgence.
[Image: USDA scientist monitoring fly pupae. Caption: Continuous efforts are critical to keep the parasite contained.]
The battle against the screwworm highlights the delicate balance between human activity, ecosystems, and global health—a challenge requiring innovation, collaboration, and relentless effort.
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