Yes, a small U.S. government program has kept flesh-eating screwworms out of the country for decades. Here's how.

The claim is that a modest government program has kept flesh-eating screwworm flies out of the United States for decades. That claim is true, and the details make it more impressive, not less.

The New World screwworm (Cochliomyia hominivorax) is a parasitic fly whose larvae burrow into and consume the living flesh of warm-blooded animals — including humans. Before eradication, it caused catastrophic losses to American livestock. The USDA's solution was the Sterile Insect Technique (SIT), first described by USDA entomologist E.F. Knipling in a 1955 paper in the Journal of Economic Entomology. The method is elegant: breed enormous numbers of male flies, sterilize them with radiation, and release them into the wild. Females that mate with sterile males produce no offspring. Flood the population with enough sterile males and the wild population collapses. By 1966, according to USDA APHIS, screwworm was fully eradicated from the continental United States.

The program then pushed the barrier southward over the following decades — Mexico was cleared by 1991, Guatemala and Belize by 1994, Honduras and El Salvador by 1996, Nicaragua by 1999, Costa Rica by 2000 — until a permanent barrier zone was established in Panama in 2006, according to USDA APHIS records. The entire operation runs through a single mass-rearing facility that, per FAO (2002), produces up to 500 million sterile flies per week. The annual budget for the Panama barrier zone has been approximately $12–15 million, according to USDA records — a number that looks almost absurdly small against the $335 million in annual U.S. livestock losses that Wyss (2000) estimates the program prevents.

The strongest version of a skeptical pushback would be: is this really "small," or does that framing undersell the broader binational infrastructure involved? It's a fair point. The program is a genuine U.S.-Mexico-Central America cooperative effort, not a single office in Washington. But "small" holds up on the metrics that matter: one production facility, one barrier zone, and a budget that is a rounding error compared to the livestock industry it protects. The operational footprint is genuinely narrow for what it accomplishes.

The 2016 Florida Keys outbreak, documented by Thomas et al. (2017) in the Journal of Medical Entomology, is the program's most instructive stress test. Screwworm reached Key deer — an endangered species — in what was the first U.S. incursion since 1982. It was detected, targeted with sterile fly releases, and suppressed. The episode confirmed two things simultaneously: the barrier is not impenetrable, and the response capacity works. It also demonstrated that without the ongoing program, re-invasion is not a hypothetical.

The manipulation pattern to watch for runs in the opposite direction from most misinformation: this story gets distorted not by exaggeration but by omission. Critics of government spending rarely mention programs like this one, because a cost-benefit ratio this favorable doesn't fit a narrative of bureaucratic waste. When someone argues that no government program delivers value efficiently, this is a precise, documented counterexample — eradication of a flesh-eating parasite, held for six decades, for roughly the cost of a mid-sized county's annual budget.