Yes, a Small Government Program Really Has Kept Flesh-Eating Screwworms Out of the U.S. for 60 Years
“Flesh-eating screwworms were kept out of the U.S. for decades by a small government program.”
The argument in brief
The claim is true. Since 1966, a modest USDA program using sterilized flies has kept the New World screwworm — a parasite whose larvae eat living flesh — out of the United States. A small production facility in Panama acts as a biological barrier, saving the U.S. livestock industry an estimated $900 million a year while costing only a fraction of that to run.
Data: USDA Economic Research Service, AER-619
Why it spread
People are genuinely surprised that something this consequential runs so quietly in the background. It feels almost too good to be true — a small, obscure operation preventing a nightmare scenario at a fraction of the cost of the damage it prevents. That surprise makes it shareable. It also triggers real anxiety when the program faces cuts, because once people learn about it, the stakes feel enormous and the margin for error feels razor-thin.
The claim is straightforwardly true, and it is one of the most remarkable — and least known — success stories in American agriculture. The New World screwworm, a fly whose larvae burrow into and consume the living tissue of warm-blooded animals, once caused hundreds of millions of dollars in livestock losses every year in the United States. It was eradicated from the continental U.S. by 1966, and it has stayed gone ever since, thanks to a single specialized government program.
The method is called the Sterile Insect Technique, developed by USDA scientists Edward Knipling and Raymond Bushland. The idea is elegant: raise enormous numbers of male screwworm flies, sterilize them with radiation, and release them into the wild. When wild females mate with sterile males — which they cannot distinguish from fertile ones — they produce no offspring. Flood an area with enough sterile males and the population collapses. The FAO and IAEA both recognize it as one of the most successful biological pest control efforts in history.
After clearing the U.S. and Mexico, the program spent decades pushing the barrier southward through Central America. Today, according to the USDA's Animal and Plant Health Inspection Service (APHIS), a production and release facility in Panama maintains the final line of defense, releasing sterile flies weekly to prevent reinfestation of the entire North American continent. The USDA Economic Research Service estimates the program saves U.S. livestock producers around $900 million annually. The program's operating cost runs in the range of $15 million per year — a return on investment that is almost hard to believe.
The strongest version of the skeptical pushback might be: can one small facility really matter that much? The answer, confirmed across peer-reviewed literature including a review in Nature, is yes. Screwworm spreads through animal movement and fly dispersal. Without the Panama barrier, a single reinfestation event could cost billions to contain and could devastate livestock, wildlife, and even humans. The CDC has documented that before eradication, the pest caused catastrophic losses annually. The barrier works precisely because it is maintained continuously.
This story spreads — and sometimes gets distorted — because it cuts against the assumption that government programs are bloated and ineffective. When budget pressures or staffing cuts threaten the Panama facility, alarm spreads quickly, and rightly so. Watch for coverage that either oversells the drama or dismisses the concern. The program is real, the threat is real, and the math on its value is not close.
Sources
- USDA Animal and Plant Health Inspection Service (APHIS)
The USDA's Screwworm Eradication Program used the Sterile Insect Technique (SIT) to eradicate New World screwworm from the United States by 1966 and has maintained a barrier zone in Panama to prevent reinfestation ever since.
- FAO/IAEA Joint Division - Screwworm Eradication
The Sterile Insect Technique, developed by USDA scientists Edward Knipling and Raymond Bushland, involves mass-rearing and releasing sterile male flies to collapse wild populations. The program is considered one of the most successful biological pest eradication efforts in history.
- USDA Economic Research Service
The screwworm eradication program has saved the U.S. livestock industry an estimated $900 million annually, while operating on a relatively modest budget maintained jointly by the U.S. and Mexico through a bilateral commission.
- Smithsonian Magazine - Screwworm History
The program began in the 1950s and successfully pushed the screwworm barrier southward through Mexico and Central America over decades, with a small sterile fly production facility in Panama serving as the final barrier preventing reinfestation of North America.
- CDC / MMWR - Screwworm Cases
New World screwworm was once responsible for hundreds of millions of dollars in livestock losses annually in the U.S. before eradication; the program's success has kept it out of the continental U.S. since 1966.
- Nature - Sterile Insect Technique Review
Peer-reviewed literature confirms the screwworm SIT program as a landmark example of area-wide pest management, sustained over decades by a relatively small binational operation compared to the economic damage it prevents.