The screw worm outbreak is affecting more than just cattle.

From Marketplace in New York, I'm Kimberly Adams.

Both Mexico and the United States have now had cases of cattle infested with New World Screwworm,

a little fly that will eat the flesh of a live animal if left untreated.

The government declared the screw worm

eradicated in the U.S. back in the 1960s. So when cases started spreading in Mexico in late

2024, the U.S. restricted the import of live animals. Now Mexico is responding in kind.

Marketplace's Caitlin Tan reports. The Santa Teresa livestock port on the Mexico- the Mexico-US border used to be bustling with a couple thousand animals crossing a day. But now? Oh boy, noticeably different. Very quiet. Very quiet. David Anderson was there recently. He's an economist at Texas A&M. He says it got a lot quieter when the U.S. banned cattle coming in from Mexico.

But up until this week, horses were still moving from the U.S. into Mexico, primarily for slaughter.

We export horses to Mexico to the tune of over 500 head a week this year.

And that has abruptly stopped.

We've had reports that there are horses sitting in the Texas stockyards at the Mexico border.

Emily Stearns is with the nonprofit American Horse Council.

She says there's also thousands of riding horses traveling between both countries.

Those are horses for racing, for ranch work, sales horses, camp horses, all kinds of stuff.

Also, horses used for jumping events.

There was a youth championship in Michigan last year.

And she says the spread of screwworm impacted who could compete.

The Mexican team couldn't come. The kids couldn't come.

And now no horses will be crossing the border in either direction.

I'm Caitlin Tan for Marketplace.

Music We've been talking all week about the headwinds facing rural health care.

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