The screwworm is finally set for a full-scale US invasion, as it has approached so closely to us that the CDC is now telling U.S. healthcare workers to stay alert.
Back in December 2024, we reported that the flesh-eating human parasite known as the screwworm was spreading across Central America. By June 2025, they were devastating cattle populations in Honduras, while eating many poorer residents alive.
In July 2025, we reported that the US Department of Agriculture was teaming up with the Mexican government to breed hundreds of millions of sterile male flies to release over Texas and Mexico to breed with the screwworm.
This would create null pregnancies in the hope of cutting down their numbers, just as the same plan did back in the 1960s and 70s. Then, by August, the first human case of the flesh-eating screwworm parasite was confirmed in the United States.
What is a Screwworm, and Why Are They Dangerous?
As you might’ve guessed from the context above, the screwworm isn’t actually a worm. It’s the larval stage that will fly and lay its eggs in open wounds and mucous membranes of warm-blooded animals. When the larvae hatch, they eat their host alive.
Farm animals are usually the first targets, before spreading to cats, dogs, and eventually, humans. If left untreated, the infection can kill a full-grown cow in about a week.
Screwworms had been all but entirely eradicated after the initial scorched-earth campaigns of the 1960s and 70s. But the US, in typical U.S. fashion, figured the problem was solved forever, so it got lazy and stopped all maintenance efforts.
The problem—surprise, surprise—eventually returned in full force, and now it’s standing on our doorstep. Decades of negligence is ready to quite literally bite us in the a—, and probably take a big honkin’ chunk out of it, too.
The CDC now warns that unregulated cattle movement, expanding farmland, and a warming climate may all be helping the parasite move faster and farther. While they do pose a degree of threat to humans, their first victims are usually livestock.
There are billions of dollars worth of livestock hanging out in Texas, with potentially billions of screwworms licking their lips waiting to sink their teeth into them.
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