Brushing Up On Tropical Diseases

Dengue fever, malaria and other tropical diseases took center stage at the American Society of Tropical Medicine and Hygiene conference. Nathan Seppa of Science News offers details, including a strange story of palm trees, fruit bats and human infection.

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IRA FLATOW, host:

This is SCIENCE FRIDAY from NPR News. I'm Ira Flatow. A little bit later in the hour, living and working in space, your own personal solar power station and our video pick of the week.

But first, this week, the annual meeting of the American Society for Tropical Medicine and Hygiene has been going on in Washington. And as its name implies, researchers are presenting studies of malaria, Dengue fever, many other diseases that are not very common here in the United States but are major health threats in other parts of the world. Science News reporter Nathan Seppa has been attending the meeting, and he's here to give us some of the highlights. You can read his stories from the meeting at sciencenews.org. He's in our NPR studios in Washington. Welcome to the program.

Mr. NATHAN SEPPA (Reporter, Science News): Thank you.

FLATOW: Thank you. What is tropical medicine to people who don't know what it is?

Mr. SEPPA: Well, tropical medicine is anything that makes you sick in the tropics. When you walk through one of these conferences, it's kind of a trip back to your eighth-grade science class, seeing all these scourges that you learned about as a kid: sleeping sickness, Dengue, yellow fever, you name it.

FLATOW: Now, we - one of the main tropical diseases that kills a lot of people every year is malaria. Is there news about malaria at this meeting?

Mr. SEPPA: Yeah, malaria is kind of the granddaddy of them all. It's a huge disease in terms of impact, infecting hundreds of millions every year and probably killing about a million people. And in this case, the news is not particularly good. There have been signs of malaria in Southeast Asia becoming resistant to the best-known drug used against it, something called artemisinin. And those signs have been confirmed, and in fact, it seems to have expanded a bit. There had been one hot spot on the border of Cambodia and Thailand, which has been talked about over the past few years, and what they're telling us now is there are other ones, other flashpoints such as one in Vietnam, a couple along the Burma border with Thailand and China. And this is all bad news.

FLATOW: Because malaria kills millions of people.

Mr. SEPPA: That's right. And so the real risk is that it'll somehow - this resistant strain of malaria will somehow spread to other parts of the globe, and from there on, there's no stopping it. This has happened before. Malaria has a real history of beating drugs, and all the resistant strains of malaria are resistant to all the former drugs, and all the still-used drugs but maybe not front-line drugs anymore, have started somewhere and spread to other areas.

FLATOW: You're covering a story about a lesser-known virus called the Nipah.

Mr. SEPPA: That's right.

FLATOW: Tell us about that. It's pretty nasty, huh?

Mr. SEPPA: Yes. Whereas malaria will make you mighty sick, Nipah is much more deadly. Luckily, it's a lot more rare. Nipah's a curious story. It's a virus that was just really identified about 10 years ago. And in Malaysia, people working with pigs had apparently caught it from working with the animals. And the death rate was substantial, but what it turns out, they've learned over the past decade is that it's basically a bat virus. It's carried by fruit bats, which are common in South Asia, Southeast Asia. And the study that I'm looking at here is out of Bangladesh, where they found Nipah infections, and they had to sort out where they came from. And it turns out they had come in through a sort of indirect contact with fruit bats.

The - I should back up and explain something about a delicacy in Bangladesh, which will make sense out of this story. Basically, people love to tap into palm trees and get a hold of the sap, which is a delicacy and a very sweet fluid, and this is a favorite in rural parts of Bangladesh mainly. And unfortunately, the fruit bats like it, too. So you can put two and two together, and they figured out in the past couple years now that fruit bats had been tainting some of the sap being collected from these trees with either saliva or other bodily fluids, and there is a way to keep fruit bats off these collection devices.

They have a little - the cut a groove into the palm tree, and they collect it in pots, and people have been bothered by bats before getting into their collection apparatuses. And basically, what - they went back and talked to folks in the bush and said, you know, have you ever gotten around this? And some of them said yeah, yeah, we used to build these bamboo netting over them.

Well, scientists being scientists, they got them to make one for them, used it as a prototype and ran a rigorous little study, complete with a control group of trees that didn't have a little bamboo skirt covering the collection devices and then trees that did, and found that they worked quite well.

FLATOW: Wow.

Mr. SEPPA: It's actually an excellent low-tech device and a way that may stop Nipah in Bangladesh.

FLATOW: So you don't come out of these meetings thinking gee, I'm sick with all these diseases, I have the symptoms for all of them, like you do with other meetings, right?

(Soundbite of laughter)

Mr. SEPPA: No, it's a scary prospect, I've got to say, yeah. It isn't entirely bad news, though. I should say there's an encouraging little bit about this. And I think down the road, a couple other things that you see at this meeting is the vaccines that are being developed both for malaria and for Dengue, which you mentioned earlier. And I think in the next two or three years, a lot of that's going to be ready for primetime, and the news may change.

FLATOW: All right, thank you very much.

Mr. SEPPA: Thank you.

FLATOW: That's great reporting. Nathan Seppa, who is a science reporter at the meeting, from Science News. And you can catch his stories at sciencenews.org.

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