Zika Linked to Deforestation and Climate Change
Evolutionary biologist Robert G. Wallace says we are seeing the reemergence of mosquito-borne viruses such as dengue, yellow fever and malaria
SHARMINI PERIES, EXEC. PRODUCER, TRNN: Welcome to the Real News Network. I’m Sharmini Peries coming to you from Baltimore.
Last week the World Health Organization called the spread of the Zika virus an extraordinary event, and declared it a global emergency. Zika is in the category of vector-borne diseases, transmitted by mosquitoes, whose population surge and bite more frequently in hot weather, and thrive particularly after droughts and extreme weather conditions. The WHO says they are expecting 4 million cases of the infection by the end of the year. It is Latin America that is currently experiencing the brunt of the epidemic, and so far Brazil is the hardest-hit country. There has been more than 4,000 cases of microcephaly, which is the birth defect caused by Zika, and they are 20 times the number from the previous year thus far recorded.
There is currently no cure or vaccine against the Zika virus. Some scientists are making the connection between the rise of Zika virus and climate change. With us to discuss this new surge of the Zika virus is Rob Wallace. He is an evolutionary biologist and public health expert visiting the Institute of Global Studies at the University of Minnesota. Rob, thank you so much for joining us.
ROB WALLACE: It’s a pleasure to be here, although I wish it was under better circumstances.
PERIES: Yeah, me too. So let’s begin with describing for us how the Zika virus came about in the first place.
WALLACE: Well, the Zika virus was identified–it’s named after the Ugandan forest the virus was first characterized in in 1947. The virus subsequently made its way across the equatorial belt to Southeast Asia. And in 2014 it made its way to French Polynesia, and reached Brazil last year, which researchers have hypothesized coincided with the World Cup, where thousands of fans from around the world convened. There’s some phylogenetic analysis that’s looking into genetic sequences of all of the, of the virus, and it’s apparent that the Brazilian strain is Polynesian in origin.
PERIES: And is there any connection between the Zika virus to the current work you’re doing by way of climate change and the various kinds of mosquito-driven diseases that are rising as a result of clear and, clearing the forest, for example?
WALLACE: Well, certainly there’s been some attention in the last few weeks directed to the ecological and environmental inputs into the, the rise of Zika, and the reemergence of many of the flaviviruses that are mosquito-borne, that we thought we had handled. But Dengue, yellow fever, chikungunya, malaria, are going full bore. It has been considerable focus on climate, and certainly as the planet warms up the biogeographic extent to which mosquitoes can emerge widens toward the poles.
But in addition, and this is something that really hasn’t been talked about too much, deforestation has a very important part to play in this, I think. I mean, there has been discussion of deforestation. What deforestation does is it rips out the forest in such a way, and replaces it with kind of an agriculture, or a wasteland that is, mosquito species are very good at reproducing in. We end up with all sorts of pools of water that allow the female to leave their eggs in, and produce millions and billions and trillions of offspring.
PERIES: Now, during the breakout of the ebola virus there was also this connection made between bats, the clearing of forests and the bats coming in contact with humans. Is this what is happening with the Zika and the mosquito?
WALLACE: Yeah. Well, I think one of the things that we have to realize, that Zika is, it’s something of an emergency right now. We’re all focused on it, as we should be. Most of the symptoms of a Zika infection aren’t really that problematic. Flu-like syndrome, fever, rash, joint pain, sometimes conjunctivitis. It’s a comparatively mild infection, as far as these diseases go. It’s been described as a kind of beginner’s chikungunya. However, some adults suffer from Guillain-Barre, which is an autoimmune disease, an inflammation of peripheral nerves that lead to progressive weakening of the legs and arms, even to the point of paralysis.
But I think, I think the thing that really has gotten our attention, as it should be, is this microcephaly that you began our interview with. And you know, babies are being born with abnormally small skulls, and with a definitional impact on brain development. And that has a particular, strikes a particular fear in us, it kind of engenders a kind of Children of Men dread about it.
But that’s–and we should focus on this as an emergency for those very reasons. But if you’ve noticed in the last 10, 20 years, we’ve been kind of jumping from one emergency to the next. It began with avian influenza, this latest round. Jumped to SARS, and then to MRS, and now to ebola, and now we’re on to this season’s outbreak, which is Zika. And I think, I think as much focus has been on kind of a broader, structural discussion of, of how these things may actually be related to each other. And it’s my view and my colleagues’ that there’s something fundamental changing in the environment on the planet. We’ve been so focused on climate change, but I think deforestation has a primary role to play in the emergence of many of these pathogens.
Forests are complex ecologies, and if you’re a pathogen in the forest it’s really hard to kind of line up a whole bunch of, a host, and string together a chain of transmission that will allow you to broadcast your way out as a regional threat.
PERIES: There’s the clearing of forests, but there’s also the higher temperature, altered by emissions and so on, that’s also having an effect on these kinds of diseases. Explain that a bit.
WALLACE: Well, I mean, as I said previously, you know, you increase the temperature of the planet, and it, you know, mosquito are primarily stuck to a band of, the kind of, the equatorial band around the planet. And if you increase the planet then you increase the size of that band, and that band stretches out toward the two poles. So there, there is, in essence, an impetus for the, for these mosquito-borne pathogens to be able to extend their geographic extent.
But for the most part, that in itself, I believe, isn’t enough. And as I was speaking of previously, the forest has a capacity to lock in these kind of pathogens from really extending out. I mean, if you go back to Zika, you know, it was isolated in a, in 1947 in this kind of Ugandan forest. But it was isolated in a particular type of mosquito, Aedes africanus species. And there’s a public health physician by the name of Amy Vittor who describes in a recent piece she published in the Conversation, in which she describes that the Aedes africanus is the forest relative of the Aedes aegypti and Aedes albopictus, which are both the mosquitoes that are involved and implicated in the spread of Zika.
And so these mosquitoes, those two latter mosquitoes that are transmitting Zika, are associated with the forest that’s been disturbed by deforestation, by logging, by mining, by monoculture crops. And they are, they are also associated with urbanization, a kind of [edge] urbanization, in which the urban edge creeps deep into the, into the forest itself. So very much, like for Dengue and chikungunya, which are also carried by these mosquitoes, there’s an ecotypic shift in Zika. It’s going, moving from a forest into the farm and into cities. And that’s really intimately related to anthropogenic impact.
So the forest, you know, it’s a source of many of these infections. And when you think, oh, the forest, it’s a terrible place, because it’s where many pathogens circulate, and then that is true, but you know, knocking down the forest is not the way to get rid of all these pathogens. I mean, it’s one way most of the pathogens, if you were to get rid of the forest, would die out because their hosts died out. But many of those pathogens are in hosts that have incredible behavioral plasticity, and they have the capacity to be able to, you know, make do with circumstances not of their own making. And so mosquitoes are an excellent example. You might–some mosquitoes may be able to adapt to the new environment. Some, you might have a selection going on, where some species of mosquito do better in these disturbed environments than the other.
Now, you mentioned ebola, and I think it’s another excellent example of that. Ebola tends to circulate among frugivore bats in Central or Sub-Saharan Africa. And for many decades you would have an unfortunate spillover into a gorilla troop or into a local village, would be taken out. But that’s where it would end. That’s where it would stop, because it didn’t have the chain of susceptibles that needed to turn into a regional threat.
And this is what happened–it’s our view that this is what happened in West Africa. Once West Africa began to be seriously engaged in a kind of neoliberalization of the forest, where the forest has opened up to being, to being logged by multinationals, to being mined, to–.
PERIES: Rob, let’s take that up. That’s a good point you take up. There are two other categories I think we should discuss, and in our next segment let’s deal with first how it’s transmitted and the dangers of it and the consequences of it, and if there’s any way of stopping it. And then in a third segment, let’s take up the issue of neoliberal economics and the impact that has on these kinds of diseases moving forward. So please join me for our next segment with Rob Wallace.
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