What Is the New World Screwworm? (And What It Means for US Beef Prices)

The New World screwworm is a parasitic fly whose larvae burrow into the living flesh of warm-blooded animals and can kill a full-grown cow in a week. It was eradicated from the United States in the 1960s. It is back, surging in 2026, and already affecting US beef supply and prices.

Here is how we beat the fly the first time (with radioactive flies and zero AI assistance), why it is back, what it means for what you pay at the grocery store, and where the replacement beef will come from. None of the options are great.

What the New World screwworm actually does to cattle

This week I heard that (yet again) America is being invaded by a flesh-eating parasite.

It's a fly whose larvae (aka maggots) burrow into the living flesh of warm-blooded animals and eat them from the inside out.

They can do this to all kinds of mammals, but particularly like going after cattle.

And if you like eating beef as much as these maggots do, boy have I got a hot deal for you! Jk, I'm not going there. 😂

Left untreated, they can kill a full-grown cow in about a week.

This is obviously….. less than great. Not ideal.

How we beat the New World screwworm the first time (with radioactive flies)

Now, we did already beat the flies once.

Back in the 1950s, USDA scientists figured out that female screwworm flies only mate one time in their whole lives. So some certified madman of a government fly scientist proposed the following plan:

Step #1: Breed flies. BILLIONS of flies.

Step #2: Sterilize the males with radiation.

Step #3: And then dump them out of airplanes over the entire American South (and beyond)

Then the wild females mate with the sterile males, nothing hatches, and the species collapses on itself.

AND IT WORKED.

By the mid-60s the screwworm was wiped out of the United States and they made it all the way down to Panama, where to this day the Panama Fly Factory pumps out millions of sterile flies per week.

Why the New World screwworm is back (cocaine trafficking included)

But after roughly 60 years of being gone, these little demons have been reappearing with a particularly big surge this year.

There's a lot of reasons that this is happening:

• Shifting weather patterns
• Changing migratory routes due to weather changes and the disruption of habitats
• The closure of Fly Factories in other Central American countries since the fly was considered to be eradicated
• Oh and, ILLEGAL DEFORESTATION AND CATTLE RANCHING TIED TO COCAINE SMUGGLING AND MONEY LAUNDERING

It's…. complicated.

Why this matters for what you pay at the grocery store

Flesh eating monsters going after cows would always be bad news, but consider the particular context of this year.

The American cattle herd is already the smallest it's been since the early 1950s. Beef prices at the grocery store are already at all-time highs. The whole system is running with zero slack, and now there's a flesh eating parasite that can take out a cow in a week.

Thankfully, here in the northeast we're well insulated from the physical implications of the screwworm (they don't handle climates with true winter).

But no one in the country is insulated from the economic impact.

Further outbreak will mean suspending cattle imports from Mexico and imposing quarantines in impacted parts of Texas. This will drive up cattle and beef prices everywhere.

The message is that we're looking at disruption, price increases, and more general weirdness and volatility in cattle and beef markets that have been running wild for years.

I'm not telling you to panic.

Screwworm is treatable when it's caught, and they are mobilizing to breed vastly more of the sterile flies in new facilities in Texas and Mexico (this is the one situation where it's pretty awesome that flies multiply so fast).

But I am telling you that this is happening at a moment when the industrial beef supply chain has no shock absorbers left.

Things are going to get weird.

Where the replacement beef will come from (none of the options are great)

Plus, as we've learned during past disruptions, the big meatpackers tend to fill the gap with beef from somewhere. So, there's the matter of "where is the replacement beef gonna come from?"

Do they slaughter cattle younger to meet demand and make the future cattle supply even tighter?

Become more reliant on drugs, additives, etc. to finish cattle even unnaturally faster?

Increase beef imports from other countries with "questionable" quality and animal welfare standards?

Roll out some kind of lab-grown meat and/or just figure out how to feed everyone the leftover female flies from the factories?

Not a bunch of stellar, yummy choices on that list.

(For more on what "fill the gap with beef from somewhere" actually looks like at the grocery store, here's why grocery store beef is watery and who's profiting from it.)

If you'd like to limit your family's exposure

So, if you'd like to limit your family's exposure to whatever the hell is about to happen in the supply chain, you can reserve a Beef Share with a free chest freezer here.

(Worried about whether you'll get through it all before the next disruption? Here's how long beef lasts in the freezer. Spoiler: 18+ months with the right setup.)

P.S. Next time you have a rough week at work, remember that there are people whose entire job is breeding billions of flies, radiating them so they cannot make babies, loading them onto airplanes, and dumping them over Texas and Mexico.