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AUDIE CORNISH, HOST:

From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish.

MELISSA BLOCK, HOST:

And I'm Melissa Block. It's Mardi Gras, Fat Tuesday, time for dancing, eating and, of course, drinking - sometimes a lot of drinking. Now, as humans, we pay a price for drinking alcohol. Tomorrow's hangover, or worse.

But, as St. Louis Public Radio's Veronique LaCapra reports, for young fruit flies, alcohol may be just what the doctor ordered.

VERONIQUE LACAPRA, BYLINE: Fruit flies. You know, they're those pesky little guys that show up when you leave apples or bananas sitting around for too long on your kitchen counter. We may find them annoying, but Todd Schlenke can't get enough of them.

TODD SCHLENKE: I've been collecting flies in my backyard for a long time, sort of as a hobby.

LACAPRA: Schlenke is an evolutionary geneticist at Emery University. He studies fruit flies and their mortal enemy: tiny, parasitic wasps.

SCHLENKE: These little wasps that lay their eggs in the fly and if the fly isn't able to kill them, the wasps hatch out and eat the flies from the inside out.

LACAPRA: Schlenke says since fruit flies lay their eggs on rotting, fermenting fruit, the larvae that hatch out can sometimes find themselves swimming in alcohol and that, he says, got him thinking.

SCHLENKE: I wonder if the alcohol can be used by the flies to protect them from being killed by the wasps.

LACAPRA: Schlenke says the first thing he needed to do was test how well the wasps could hold their liquor. Turns out, some wasps can't even handle inhaling the fumes. No, they don't start slurring their words and hitting on that cute firefly at the end of the bar, but close.

SCHLENKE: They basically get drunk. They can't stand up right and they can't perform their normal functions, which is to lay a bunch of eggs in fly larva and try to complete their life cycle.

LACAPRA: That means wasps are less likely to attack flies swimming in boozy fruit juices. But what if a wasp does succeed in laying its eggs inside a young fly? Schlenke found that if the fly larvae drink the alcohol, they can actually kill off the wasps developing inside them.

SCHLENKE: And so the next question we asked was, you know, do flies know that? Do they purposely consume alcohol once they're infected in order to kill those wasps living inside of them? So we gave the flies a choice.

LACAPRA: In one half of the Petri dish, a delicious cocktail of baker's yeast, molasses and six percent alcohol. In the other half, the alcohol-free version. Infected flies overwhelmingly chose the booze.

SCHLENKE: Essentially, the fruit flies are self-medicating. They realize when they're infected and they're seeking out a substance that helps cure them of that infection and, in this case, that substance is alcohol.

LACAPRA: Self-medicating does exist in the animal kingdom. Insects, birds and primates all have been known to eat special plants to rid themselves of parasites or other ailments, but Schlenke says this is the first example he knows about of animals using alcohol as a medicine.

And that raises the question, what about humans? After all, we get our share of parasitic diseases, too, everything from hookworm to malaria. Could alcohol help us get rid of parasites?

(SOUNDBITE OF PHONE RINGING)

LACAPRA: I decided to call a doctor to try and find out. Hello, Dr. Hotez.

DR. PETER HOTEZ: Hi, how are you?

LACAPRA: Hi. I'm great. Dr. Peter Hotez is the dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston. He's also president of the Sabin Vaccine Institute, which develops vaccines for parasitic infections. If anybody knows parasites, it's this guy.

So my question is, is there any chance a night of binge drinking would help somebody who had been infected with something like the malaria parasite get rid of it?

HOTEZ: Well, it seems to, actually, to have the opposite impact, so...

LACAPRA: Hotez says studies of alcoholics show that chronic drinking can make some parasitic infections much worse. But what about just a little alcohol? Can that help?

HOTEZ: The answer as far as we can tell is no. The closest thing that comes to it is the gin and tonics that were used during British Colonial days to treat malaria. It wasn't because of the gin. It was because of the tonic, which contained quinine. That had an anti-malarial effect.

LACAPRA: Oh, well. It was worth a shot or two or three. For NPR News, I'm Veronique LaCapra.

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