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Daniel Streicker: What If We Could Stop A Virus At Its Animal Source?

Dec 18, 2020

Part 3 of the TED Radio Hour episode Making Sense of 2020

MERS, Ebola, and COVID-19—the viruses that cause these diseases likely have the same patient zero: bats. For researcher Daniel Streicker, the key to preventing an outbreak is the bats themselves. A version of this segment was originally heard in the episode, Inoculation.

About Daniel Streicker

Ecologist Daniel Streicker focuses his research on animal-borne diseases. He is a Wellcome Trust Senior Research Fellow and head of the Streicker Group at the University of Glasgow Institute of Biodiversity, Animal Health & Comparative Medicine and the MRC-University of Glasgow Centre for Virus Research.

His research uses a range of approaches including longitudinal field studies in wild bats, phylodynamics, machine learning, metagenomicsand epidemiological modeling.

In 2013, Streicker was awarded the Science and SciLifeLab Prize for Young Scientists for his work on the transmission of the vampire bat rabies virus in Peru. He received his Ph.D. in ecology from the University of Georgia.

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MANOUSH ZOMORODI, HOST:

On the show today, the people who helped us make sense of 2020 - and back when we were first learning about COVID-19 and the virus that causes it, the immediate question was, where did it come from? What was the source?

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UNIDENTIFIED REPORTER: Our scientists are hunting for the origins of this novel coronavirus.

ZOMORODI: Attention immediately turned to bats.

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UNIDENTIFIED REPORTER: So far, experts suspect that bats could be the likely hosts.

ZOMORODI: This new coronavirus likely came from bats. And actually, bats have been patient zero for a lot of viral outbreaks.

DANIEL STREICKER: Ebola virus, Nipah virus, Hendra virus, SARS and likely this new coronavirus SARS 2.

ZOMORODI: This is ecologist Daniel Streicker. He studies animal-borne diseases.

STREICKER: It's maybe not unexpected that bats have that number of viruses, just given the number of bat species that there are in the world. There's over 1,500 species. So it kind of makes sense that they should have some virus that jump into people.

ZOMORODI: Daniel studies how viruses travel from animals to humans, specifically from bats to people.

STREICKER: Yeah, absolutely. There's intense interest in knowing whether there is something about the immune system of bats or even, like, the life history or ecology of bats which somehow makes viruses that, if they're in people, become more pathogenic.

ZOMORODI: Daniel started focusing on bats back in 2006. He tells his story from the TEDMED stage.

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STREICKER: And that was when I first heard about an outbreak of mysterious illness that was happening in the Amazon rainforest of Peru. The people that were getting sick from this illness - they had horrifying symptoms, nightmarish. The most tragic part of all was that many of the victims were children. And of all of those that got sick, none survived. It turned out that what was killing these people was a virus. But it wasn't Ebola. It wasn't Zika. It wasn't even some new virus never before seen by science. They were dying of rabies. And what all of them had in common was that as they slept, they'd been bitten by the only mammal that lives exclusively on a diet of blood, the vampire bat.

ZOMORODI: I mean, when I hear that, that is absolutely terrifying. And what was your reaction when you first heard about this? What did you think?

STREICKER: It did surprise me in the sense that I knew that vampire bat rabies was a thing that happened in the Amazon. But at that point, I didn't think of it as a disease that can enter into a community and then kill 10 or 20 children within the course of about a month. So that really changed my thinking on it and made me realize there's something going on here, and that was what I wanted to work out.

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STREICKER: So I jumped onto a plane and flew off to Peru, looking for vampire bats. You see, all we had to do was show up at a village and ask around, who's been getting bitten by a bat lately? And people raise their hands Because in these communities, getting bitten by a bat is an everyday occurrence - happens every day. And so all we had to do was go to the right house, open up a net and show up at night and wait until the bats tried to fly in and feed on human blood.

ZOMORODI: Wait. OK, so wait. Bats just fly in when people are sleeping and feed on them? Like, people don't feel them?

STREICKER: Right, so the way that people get bitten is literally as horrifying as it sounds. It's bats entering their houses in the night and biting them. Usually, bites are on the head or the toes. And their saliva has anticoagulants in it, so the blood just continues to flow. And so they're not really sucking blood, rather just lapping it up as it flows out of the people that they've bitten. And it's quite shocking. But you can ask people, and they never seem to wake up when this happens.

ZOMORODI: Wow.

STREICKER: And partly, it's that the bats seem quite good at picking out people that are really deep in sleep. And they probably do that by listening to breathing patterns. So they can work out who's really well-asleep...

ZOMORODI: Huh.

STREICKER: ...And then sneak up to them in a very stealthy way, make a small wound which doesn't cause too much pain and then just lap up the blood. They are supremely well-adapted to a lifestyle of feeding on blood.

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STREICKER: Since we were working all night long, I had plenty of time to think about how I might actually solve this problem. If we could somehow anticipate when and where the next outbreak would be, that would be a real opportunity, meaning we could vaccinate people ahead of time before anybody starts dying. But vaccination is really just a Band-Aid. At the end of the day, no matter how many people we vaccinate, we're still going to have exactly the same amount of rabies up there in the bats. But if we could somehow reduce the amount of rabies in the bats themselves, then that would be a real game changer.

ZOMORODI: So step one - Daniel started tracking the bats. Rabies survives when it moves from one animal to another. And using genetic testing and tracking the bats' mating patterns, Daniel and his team could kind of forecast where the rabies would go next.

STREICKER: When the juvenile males come to maturity, they have to leave the maternal roost, the roost where they were born. And so when they do that, some of them are taking rabies with them. By looking at the genetic structure of the bats, we can get some idea of where the virus is going to spread into the future.

ZOMORODI: And that's when Daniel found something surprising. Until this point, scientists thought the Andes Mountains blocked rabies from moving from one side of the country to the other.

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STREICKER: The Andes are really tall - about 22,000 feet. And that's way too high for a vampire to fly.

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STREICKER: Yet when we looked a little bit more closely, we saw in the northern part of Peru a network of valley systems that was not quite too tall for the bats on either side to be mating with each other. We were actually witnessing, in real time, a historical first invasion into a pretty big part of South America, which raises the key question, well, what are we going to do about that?

ZOMORODI: And which brings us to step two of Daniel's plan - vaccinate the bats.

STREICKER: So in this case, we have an oral vaccine, which is embedded into a gel. And you spread that onto one or more bats, and you release them. Then the other bats will lick the first bat that you put your vaccine on. And when they consume the vaccine, they get protected against the disease.

ZOMORODI: Huh.

STREICKER: And so this is potentially a way to spread your vaccine to a much larger number of individuals than you actually had to go out and catch manually.

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STREICKER: Now, we have a whole laundry list of questions. How many bats do we need to vaccinate? What time of the year do we need to be vaccinating? How many times a year do we need to be vaccinating? They're questions that we can't answer in the laboratory. So instead, we're taking a slightly more colorful approach. We're using real, wild bats but fake vaccines. We use edible gels that make bat hair glow. And that's letting us study how well a real vaccine might spread in these wild colonies of bats. Our results so far are incredibly encouraging. They're suggesting that using the vaccines that we already have, we could potentially drastically reduce the size of rabies outbreaks.

ZOMORODI: I mean, that would be incredible. And of course, like, where my mind goes is, would it even be possible to do this with viruses like Ebola or SARS or COVID-19, or am I just being wildly optimistic here?

STREICKER: Yeah, so the challenge with some of these other viruses is that we don't always know with great certainty where they're coming from. So we might know that it's a bat virus. But we might not know which bat, or there might actually be multiple bats that are involved in circulating those viruses in the wild. The other thing that you have to think about in terms of applying ideas like transmissible vaccines is, really, is that the right strategy, given the disease that you're dealing with? If the introduction from the source is so rare and so unpredictable, then it might be that the best thing that you can do is advise general measures to reduce contacts between bats and humans or use reactive measures. So after the virus emerges, then deal with it, as we're currently doing for COVID-19.

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ZOMORODI: That's ecologist Daniel Streicker. His research focuses on animal-borne diseases. I spoke to him back in March. And you can see his entire talk at tedmed.com. On the show today, looking back on big ideas from 2020. I'm Manoush Zomorodi. And you're listening to the TED Radio Hour from NPR. Transcript provided by NPR, Copyright NPR.