Flesh-Eating Parasite Returns to Texas After 60-Year Absence

A Nightmare Returns to American Ranches

For the first time in six decades, the New World screwworm has crossed back into American territory. The U.S. Department of Agriculture confirmed the first case in a 3-week-old beef calf near La Pryor, Texas, marking the pest's return since it was eliminated in 1966. The parasitic flies lay their eggs in open wounds or body cavities of warm-blooded animals, with the hatching maggots burrowing through skin and feeding on living tissue, causing painful, foul-smelling wounds.

The flesh-eating fly poses a direct threat to Texas's $15 billion cattle industry , and the U.S. cattle herd is already at its lowest level in 75 years. The country's worst outbreak occurred in 1972 with 90,000 cases, and another outbreak of that magnitude could cost the Southwest alone more than $3 billion and raise beef prices when Americans are already paying record highs.

The screwworm is believed to have traveled from Central America to Mexico before being found in the Texas calf, evading biological barriers that have kept the pest contained for decades. Between mid-July and mid-August 2025, Mexico reported a 53 percent rise in cases , and Washington has halted cattle imports from Mexico for the past year, citing the insect's spread.

The Science of Sterile Warfare

The USDA has activated personnel on the ground in Texas to contain and eradicate the parasite, including a 20-kilometer infested zone with quarantines, movement controls and surveillance, while expediting targeted release of sterile flies to overwhelm fertile flies in the area. This approach leverages a biological quirk that proved devastatingly effective in the 1960s.

Females only mate once in their three-week lifespan, so if the male they mate with is sterile, there will be no new screwworm larvae, and saturating an area with sterile males will eventually lead to the fly's demise. Using atomic radiation, scientists expose pupae to low doses that inhibit reproductive organ development without affecting other body parts, resulting in normally developed but sterile adult flies.

The Panama facility produces 115 million sterile flies per week, and a new Texas facility will produce 300 million per week once completed in early 2026. The centerpiece of the federal response is construction of a $750 million sterile fly production facility that will produce up to 300 billion sterile flies per week, tripling current output and eliminating dependence on Mexico and Panama.

Economic Stakes and Human Risk

The financial implications extend far beyond ranching. Losses to livestock producers due to a screwworm outbreak in Texas were estimated at $732.6 million in 2024 dollars, with total economic losses reaching $1.8 billion. A 1976 outbreak in Texas caused $330 million in damage, with experts warning that a similar outbreak today could exceed $2 billion and send beef prices skyrocketing nationwide.

While livestock bears the primary burden, humans aren't immune. The most recent human screwworm case in the U.S. was identified in Maryland last year after a traveler returned from El Salvador, though the person recovered and federal health officials found no evidence of spread to others. Humans can also be infected , making this more than an agricultural concern.

The Path Forward

Officials emphasized that response plans developed over the past year are already being put into action, with Secretary Brooke Rollins expressing confidence in the teams and infrastructure built to contain this pest and push it back when possible. The success of previous eradication efforts provides a roadmap, but the stakes have never been higher.

The battle against the screwworm represents more than pest control—it's a race to protect America's food security and economic stability. With cattle numbers already at historic lows and beef prices soaring, the outcome of this biological warfare will determine whether this ancient enemy remains contained or spreads across the American heartland once again.