US to release billions of sterile flies over Mexico and Texas to combat deadly parasite

In a large-scale environmental and agricultural effort, US authorities are preparing to release billions of sterile flies over southern Texas and Mexico to combat the resurgence of the screwworm fly — a parasitic insect whose larvae feed on living tissue, threatening livestock, wildlife, and even pets.

Bloomberg reports that the US Department of Agriculture (USDA) will mass-produce adult male flies, sterilise them using radiation, and release them from aircraft. These sterile males will mate with wild female flies, resulting in no offspring and a gradual collapse of the screwworm population. Scientists emphasise that this method is far more eco-friendly and effective than traditional poison-based approaches.

Historically, this sterile insect release technique successfully eradicated screwworms from the United States and countries north of Panama decades ago. However, in late 2023, the screwworm reappeared in southern Mexico, reigniting concerns.

To bolster this campaign, a new fly breeding facility is planned to open in southern Mexico by July 2026, complemented by a distribution centre to be established in Texas by the end of 2024.

If demand surges, sterile flies will also be imported from a Panamanian factory capable of producing up to 117 million flies weekly, although scientists estimate that at least 400 million flies per week are needed to combat the infestation effectively.

Unlike most flies that feed on decaying flesh, the screwworm fly lays eggs in open wounds or mucous membranes of living warm-blooded animals, including humans. The hatched larvae then consume the host’s living tissue from the inside out.

“A thousand-pound cow can die in two weeks,” warned Michael Bailey of the American Veterinary Association, illustrating the severe threat posed to agriculture and animal health.

Researchers call the sterile fly release program one of the greatest achievements of American agricultural science, but caution against complacency.

“What we consider to be completely defeated can always come back,” said University of Florida professor Edwin Burgess, underscoring the necessity of maintaining ongoing surveillance and production facilities even after eradication.

By Tamilla Hasanova