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The domestic return of the New World screwworm, a parasite that can devastate cattle herds, happened while the Trump administration was focused on dismantling government.
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JUNE 9, 2026

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Notice of the first U.S. case of the New World screwworm in cattle has been an "oh shit" moment I've been waiting for over the past year, ever since the parasite began creeping up from Mexico. It's the kind of thing that is enormously harder to get rid of once it's here than to keep away. And that's what government had been doing diligently for 60 years, until we saddled ourselves with an administration that doesn't believe in government. This is the first lesson in the folly of that anti-government belief; I doubt it will be the last.

–David Dayen, executive editor

Eric Gay/AP Photo

Why That Next Hamburger Is Going to Cost You

The primary driver of inflation in the U.S. economy—the forever war in Iran—has not yet taken full effect. Now we’ve found an entirely new driver.


Last week, the flesh-eating parasite known as the New World screwworm was found in a calf in Texas; a second case was identified about five miles away shortly thereafter. (A third case was found in a dog.) Screwworm flies lay their eggs in the live tissue of warm-blooded animals, from livestock to pets to humans. These larvae “screw” into the animal’s flesh, and while they are not very harmful to humans, in that the horrifying effects of maggots chewing into your skin are relatively easy to notice and address, they can kill a livestock host if not treated. In a widespread infestation, one of the last resorts would be mass culling, which would obviously have huge impacts on a diminished U.S. cattle herd.


The total herd count already sits at a catastrophic 75-year low, in part because of the screwworm outbreak that broke past a firebreak in Central America starting in 2023. The U.S.-Mexico border has for the past year been closed to live cattle auctions, affecting the feeder cattle that come in through Mexico to rebuild herds. But closing the border did not stop the flies from coming.


Low cattle volumes have sent the price of beef skyward to levels not seen since the Korean War, up between 20 and 35 percent in the past year. A screwworm outbreak would seriously aggravate that spike. In other words, you probably should have ordered your last hamburgers of the summer a week ago.


An outbreak would dramatically impact ranchers who have been in a deep hole for the past decade from reduced stocks, and more recently from drought, tariffs, imports of cattle pushed by President Trump to lower the price, a war in Iran that has spiked costs of fertilizer and fuel, and now the screwworm. “The cattle producer in the U.S. has already been under extreme financial stress,” says Joe Maxwell, co-founder of Farm Action and a farmer in Missouri, where he once served in the state legislature and as lieutenant governor. “This is serious, the screwworm outbreak. But it’s even more serious because of the financial position they were already under.”


These impacts are why the U.S. worked so hard for 60 years to prevent the screwworm’s return. In an obscure yet effective government program, the government bred enormous quantities of male screwworms that it irradiated to make them sterile. It then airdropped them into the Panamanian rainforest to mate with females. Those assignations produce no larvae, eradicating the threat of northward migration. This was so successful that there hasn’t been a single identified case in cattle in Texas since 1966—until last week.

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A photo from the Prospect story.

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