I’ve been in agriculture my entire life, but until a couple of years ago, I’d never really heard much about the New World Screwworm. There’s a reason for that: we wiped it out in 1966, and that was the last time screwworm touched mainland U.S. soil. For 60 years, it was basically a ghost story, and not something we actually worried about anymore.

Spring 2026, and we’ve confirmed it in a calf, a dog, and a goat right here in America. Three cases isn’t a barn fire, but it’s smoke.

But why does a 60-year-old bug make a comeback? Even with a well-managed border, which we definitely don’t have, it only takes one infested animal, moved north, with a wound no larger than a thumbtack-sized hole.

Then add poor biosecurity across the board. DOGE cuts hit USDA’s screwworm surveillance, trapping, and rapid response budgets when we needed those programs most. They shut down the fire department in the middle of fire season, let’s not act surprised as the town burns.

And finally, rising equatorial temperatures. Winters in northern Mexico and the southern U.S. used to do our work for us. Cold snaps used to kill off wintering screwworm populations and operated as our free reset button every year. However, recent warmer winters meant flies survived, bred earlier, and pushed their range farther north.

In Latin, Cochliomyia hominivorax translates to “maneater” and tells you everything you wanted to know about the New World Screwworm. Female flies aren’t attracted to rot and garbage like houseflies; they’re attracted to blood and living flesh like sharks. Open wounds as small as a tick bite, dehorning site, navel on a newborn calf, even the eyes, ears, or mouth will work for the fly to lay eggs. Within 24 hours, those eggs hatch.

The maggots don’t just eat dead tissue; they keep burrowing deeper, twisting into live flesh like a screw- giving them their name. As they grow, they enlarge the wound, creating an opportunity for bacterial infection. A cow that looks a little off on Monday can be eaten from the inside out by Sunday. Dogs, goats, deer, and yes, even humans (particularly unhoused ones), are all vulnerable.

The last time the United States eradicated screwworms using what is called the Sterile Insect Technique (SIT). Our scientists bred millions of male screwworms in labs, blasted them with radiation until they were sterile, then released them over outbreak areas. Since the female flies mate only once in life, if they mate with a sterile male, they still lay eggs, but those unfertilized eggs never hatch… and no next generation is born.

SIT worked so well that it became one of the great success stories in agri-science. We pushed the fly out of the United States, clear down to Panama’s Darién Gap. For decades, that gap was our biological wall and the program was so successful that we started to forget why it existed. Facilities were scaled back. Funding dried up, and Elon Musk and DOGE cut the funding for a major observation program dedicated to monitoring and stopping screwworms.

In 2023, screwworm cases started spiking again in South America, and within three years, they were back in Texas. Without aggressive action right now (or a good and cold 2026/2027 winter), this fly could be widespread across the southern states within a year. Texas alone has 12 million cattle; all potential hosts. Multiply that across every state from the Atlantic to the Pacific, and you’re looking at billions in livestock losses, export bans, and damage few ranchers can absorb.

We need three things.

First, fund the barrier like our food supply depends on it, because it does. The USDA Panama sterile fly plant needs consistent money, not emergency bailouts after the fly crosses the border. Prevention is generally cheaper than eradication efforts. It’ll cost $50 million a year, and we can fight screwworm in Panama instead of at home.

Second, we need to rebuild domestic surveillance and spread relevant information. Texas, New Mexico, Oklahoma, Louisiana, and Florida need more active trapping grids and rapid-response programs that can drop sterile flies within a day of a confirmed screwworm infection case. On our ranch for years we’ve had garlic salt in the pastures, and every time cattle come through the chute, they get dewormer and/or fly prevention sprays and/or fly tags- but many outfits don’t bother with any of that.

Third, treat screwworm like the climate and trade issue it is. You can’t talk about border security and ignore biosecurity. You can’t talk about food prices and ignore pests that eat livestock alive. It follows heat and hosts, and you can build a Mexico/US MAGA Border Wall from the magma to the moon, and it won’t stop this fly.

Screw you, worm. You already cost us enough. But if we move fast, fund SIT, restore biosecurity, and stop pretending 1966 was the end of the battle, we can drive you back south again…hopefully to extinction this time.
Collin Duprel is a guest columnist for the Rapid City Post. Opinions expressed may not necessarily represent the views of the Rapid City Post, its affiliates, or advertisers.