Season 4, Episode 9: Dawn Wesson: The Growing Threat of Mosquito-Borne Diseases in a Changing Climate
Dr. Dawn Wesson, Associate Professor at Tulane University’s School of Public Health and Tropical Medicine
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Dr. Dawn Wesson, Associate Professor at Tulane University’s School of Public Health and Tropical Medicine, joins John to explore how climate change is expanding the range of vector-borne diseases. With decades of experience studying mosquito-borne viruses like West Nile and Zika, Dawn explains how rising temperatures and human movement are accelerating the northward expansion of tropical diseases. She also discusses innovative control strategies, including biological methods and emerging technologies that could help reduce disease transmission in a warming world.
“There are direct and indirect effects of climate change. One kind of obvious direct effect ... is temperate areas becoming warmer annually, and we can see northward or southward expansion of mosquito species that tend to be more tropical in distribution into more temperate areas.”
Key Topics
How Climate Change is Expanding the Range of Mosquito-Borne Diseases: Dawn explains how rising temperatures and changing precipitation patterns are driving the spread of viruses like West Nile, Zika, and Dengue into new regions as mosquitoes expand their range.
The Role of Birds and Mosquitoes in Virus Transmission: John and Dawn discuss how birds act as primary hosts for diseases like West Nile, while mosquitoes serve as the transmission vector, making climate-driven shifts in bird migration and mosquito populations critical to understanding disease spread.
How Temperature Changes Affect Mosquito and Virus Survival: Dawn describes how mosquitoes are directly affected by temperature shifts—mild winters help them survive longer, while extreme heat can either shorten their lifespan or intensify virus transmission by concentrating birds and mosquitoes around shrinking water sources.
The Connection Between Green Infrastructure and Mosquito Breeding: As cities implement green infrastructure to manage flooding, Dawn highlights how features like rain gardens and detention basins can unintentionally create mosquito habitats by holding standing water that mosquitoes can use for breeding.
Vector Control Strategies: Chemical vs. Biological Methods: Dawn breaks down mosquito control approaches, explaining how chemical larvicides, mosquito-eating fish, and predatory mosquito species are used to manage populations and reduce disease risk .
Innovative Research on Mosquito Feeding & Virus Transmission: Dawn shares her latest work using 3D-printed synthetic vasculature to study how mosquitoes feed and transmit viruses, a tool that could improve interventions for vector-borne diseases .
Links to Relevant Studies and Resources:
Learn more about Dr. Dawn Wesson and her research on mosquito-borne diseases at Tulane University’s Department of Tropical Medicine.
See the CDC’s Vector-Borne Diseases Overview to learn more about diseases transmitted by vectors such as mosquitoes and ticks.
Learn how climate change is increasing the spread of mosquito and tick-borne diseases in the CDC’s report, Climate Change Increases Vector-Borne Diseases.
Dawn discusses the role of mosquito control districts in disease prevention. Learn more from the Louisiana Mosquito Control Association.
Further Reading:
Dawn discusses the risks of climate change on vector-borne diseases. Read the CDC Report on Climate Change and Infectious Diseases.
Read about successful strategies of mosquito control using biological methods in an article from the journal Insects: “Biological Control of Mosquito Vectors: Past, Present, and Future”.
“When it gets really hot out ... and it becomes drier, water sources shrink. Both birds and mosquitoes need water. It’s sort of counterintuitive that drought-like conditions can actually drive viral amplification and infection of new hosts because everybody’s got to get to that water source, and so birds and mosquitoes become in closer contact.”
Transcript
START (AUDACIOUS WATER EPISODE 9 SEASON 4)
[MUSIC]
John: Welcome to Audacious Water, the podcast about how to create a world of water abundance for everyone. I'm John Sabo, director of the ByWater Institute at Tulane University. On today's show, the fifth transformation: how climate change is fueling the spread of mosquito-borne diseases. Rising temperatures and human movement are expanding the range of viruses like West Nile, Zika, and Dengue. My guest is Dr. Dawn Wesson, a leading researcher in vector-borne disease ecology at Tulane University. Today we'll dive into how mosquitos adapt to climate shifts and what solutions--from biological control to cutting-edge technology--could help curb the spread of these deadly diseases.
John: Dawn, welcome to the show.
Dawn: Thanks John, I'm happy to be here.
John: Cool, well, let's dive in. First question. We have an incipient project that we're hoping to get off the ground on the topic that we're going to talk about today. And I'm wondering, when you were young did you imagine that you would be doing what you're doing today?
Dawn: I had no clue whatsoever. I grew up on a farm in the Midwest, in northern Illinois, and so I was very - I didn't realize how lucky I was to be so close to nature all the time. And it's a different place now than it was that long ago, all those years ago. But it really gave me an appreciation for nature and just everything that goes on in it I guess. And so I kind of just was able to follow my passion once I found it.
John: And when was it that you were, like, "Ah-ha, this is what I’m going to do with my life?"
Dawn: Well, certainly in high school I was very interested in all things science, and I was a voracious reader of all types of things. And in college I realized that I was not destined for medical school, and I really wasn't someone who wanted to go teach high school or something like that. So I was a bio and Spanish major, and eventually I got a job where I worked on mosquito control. I was the City of Naperville's mosquito intern the year after my senior year in college. And I got to learn about mosquitos and how some people try to control them, and how to do it in a bio-friendly way. And that really got me pointed in that direction. And I just continued through a master's degree, and a PhD, and a post-doc, getting more and more focused on mosquitos and viruses. And, you know, thirty-some-odd years later I'm still here at Tulane after leaving the Centers for Disease Control in Atlanta.
John: Okay, so let's dig in a little bit on the topic for today. Can you talk a little bit about the lifecycle of one of these vector-borne diseases? Let's choose West Nile, for example, because that's the one that we're interested in working on together. Tell me about the host and tell me how it works, because I think our average listener probably doesn't know how complicated it is.
Dawn: Yeah. West Nile is one of the more complicated ones for viruses that are transmitted by mosquitos. And, well, one of the interesting things about West Nile is that it was only introduced into the United States back around the year 2000. And we don't really know how it got here, but once it got here it took off in local mosquitos. And so the normal host for this virus is a bird of some sort. So there's lots of different birds that can act as hosts--some are better at it than others. But it's basically birds, and it's mosquitos - a particular type of mosquitos that tend to feed on birds that are the basic transmission cycle, that keeps it going out where we don't see it. It's the birds and the mosquitos. And so the virus has to be able to grow in both of those different types of hosts. So the cold-blooded one, which is the mosquito, and the warm-blooded one, which is the bird. We can become infected by West Nile Virus. Generally we don't develop a high enough viremia so that if a new mosquito feeds on us it will become infected. We can get sick from it, we can die from it, especially if we're elderly or immunocompromised. But we are not a normal part of the transmission cycle for West Nile Virus.
John: That's so interesting. And I want to come back - when we get into the climate change piece of this I want to come back to that endotherm-ectotherm piece with the bird and mosquito and the interactions with changing temperature. I think that's pretty interesting. And there's the virus in there, too, which is a living organism, right? So it's a coupled ecosystem that needs conditions to be in a certain place. So we'll come back to that in a little bit. How does - pick another disease that might be different, Zika or another one--I don't know which one is the easiest--but that might have different characteristics. They're not all the same, right?
Dawn: No, they're definitely not all the same. And we tend to look at these viruses as sort of families of viruses. And the ones that are more closely related to one another, as you might imagine, have more similar types of transmission cycles. So if you take West Nile and you take Zika, even though they're somewhat closely related they have very different transmission patterns. So Zika is a human-to-mosquito-to-human transmission cycle. Birds are not involved in Zika transmission at all. And so because of that, or for that reason, Zika transmission tends to be in more urbanized types of environments where there's lots of people. So think lots of hosts. And if you've got the right mosquito there it's also a different mosquito that transmits Zika. And it likes to feed on humans vs. the ones that transmit West Nile, they like to feed on birds. And it's usually not 100% in either direction, and that's why sometimes there's spillover. That's why we can get West Nile even though those mosquitos are mostly feeding on birds. But occasionally they will feed on humans as well. So that's a different transmission cycle. And another one - another example I would say is malaria, which is a mosquito-transmitted pathogen, it's a parasite, but it's transmitted by a completely different type of mosquito. But it's also transmitted between humans and mosquitos. So lots of variability out there in terms of what mosquitos are transmitting. And of course, you know, our interest here is in how those mosquitos may react, and the vertebrate hoses as well, may react to changes in climate through time.
John: Before we go there--and that's certainly the core of this interview--talk to me a little bit about the spatial context of West Nile. Let's think about West Nile right now. In working with you over the past year and sort of getting up-to-speed on vector-borne disease, it kind of impressed me how, you know, the host for West Nile, which is a bird, may not be spatially-overlapping always with humans. Talk to me about that and how transmission happens to humans when, you know, the host is maybe in a different space and time, right?
Dawn: Yeah - no, really good question. So, you know, birds are a very diverse group themselves, and I've learned a lot more about birds from working on West Nile over the years than I knew before that. Some birds tend to be migratory--they'll maybe over-winter in one area, say, South America; and during the summer they'll fly up to Canada. And we're on one of those main flyways where birds are coming up after crossing the Gulf of Mexico. They'll land, they'll feed, they'll regenerate their energy reserves and then head north from there. And during that period of time if they're carrying a virus they may introduce one - if they're carrying West Nile they may introduce it into our area during that migration. There's also birds that are not migratory that tend to be stationary in one area. They may move around in that area, but they don't fly long distances to get away. And so our habitat here, it being subtropical, we tend to be generally a pretty good space to live year-round in for those birds. Except for the occasional freeze it's really pretty nice here for them. And so we can get, you know, annual reintroductions of West Nile bringing new variants into our area, as well as ongoing maintenance through local birds who are not leaving. So we kind of think about it as - West Nile tends to be quite seasonal here. We start to see the virus showing up in mosquitos, which we collect and test for virus in May or June. And those numbers of positive mosquitos go up through time until they usually peak around maybe mid-August, something like that. And then they start to drop off again after that. But what we don't know is how many variants are present in the environment. We know that new ones are being introduced pretty much annually. We don't routinely go in and sequence those variants to understand that. And that's something that we would really like to do to better understand.
John: Variants of the virus, right?
Dawn: Mm-hm, variants of the virus. So going back to your question about spatial distribution, the birds and the virus are probably interacting with mosquitos in the spring when birds are nesting. And you've got these nesting birds that are kind of vulnerable, they don't have many feathers, mosquitos can feed on them more easily than adult birds. And so that may be happening in treetops and out in wooded areas. And then as the amount of virus kind of amplifies going into the summer we see birds like sparrows, and crows, and blue jays becoming infected in more urban areas. And so you think about the numbers of sparrows and crows that we see in our community, and that's where you start seeing more amplification of the virus, and then that's where you start seeing more people in urban areas being exposed. But it's not just urban, it's also suburban and certainly out in rural areas you can be exposed as well. But anywhere you're outside and active and not wearing some kind of protection--either a repellant or long sleeves--is when you potentially are going to be exposed to that virus.
John: Well, that's complicated in many ways, right? Like, three different biological organisms interacting and then this space-time transmission process that is really interesting. So if you had to put 50 bucks on it would you say that West Nile came here through a person or through birds?
Dawn: I would say probably a bird or some other animal that could become infected and develop some kind of viremia. We know that people bring in birds illegally, or attempt to bring in birds illegally all the time for various purposes. And there are some animals that are imported legally that potentially could've been a source of the virus. We do know that the virus came from the Middle East, because they did sequence it the year that it was introduced and it was almost identical to an isolate that came from a goose or something from Israel the previous year. And so we have a good idea of where it came from, we just don't know.
John: How interesting. Let's transition into climate change. You know, the reason for me reaching out to you to collaborate was an interview that I did with Tom (Laviste) on this podcast early on. And when I asked him about - I asked him a real general question about climate change and human health, and what he thought the main concerns were. And number one on his list was vector-borne disease. So talk to me about, just at a real high level, what are some of the potential scenarios that we could be seeing with vector-borne disease and climate change?
Dawn: Well, there are probably - there are direct and indirect effects of climate change. So if we consider one kind of obvious direct effect, if you think about global warming, temperate areas becoming warmer annually, and we can see it northward or southward expansion depending, you know, which hemisphere you're in, expansion of mosquito species that tend to be more tropical in distribution into more temperate areas, or what we used to consider "temperate" areas that are becoming warmer. And those mosquitos potentially can carry the viruses that they're good at transmitting. That's a real obvious, easy kind of scenario to lay out.
John: Is it just the temperatures getting warmer in the summer, or is it that the winters are not as cold as they used to be and they...? Yeah, talk to me about that. What part of warming?
Dawn: It's both - it's both. And I think, you know, we just went through three days of snow and freezing weather here in New Orleans, and a lot of snow--more snow than anybody's ever seen here--and so we'll also have these extreme events that are going to go back and forth. So even though, you know, people are, like, rolling their eyes saying, "Oh, climate change, sure. Global warming, sure. Look at New Orleans." But, I mean, that is what you would expect, you know, is those sorts of outside-the-normal types of events. And our mosquitos are pretty good at getting through those types of events. I don't expect any decrease in mosquito populations this coming season. So there's a couple things there though, going back to your question. If it gets too warm that's counterproductive as far as mosquitos and viruses go. At a certain point you're not going to get anymore rapid growth of the virus in the mosquito. And that's actually what it drives--it drives how quickly the virus will amplify in the mosquito, and then can be transmitted to a new host. At a certain point that heat becomes detrimental to a mosquito and they're going to die before they can get a chance to transmit the virus to another person. So you could have - in addition to having a push you can also have a pull in terms of the effect of heat in the summer, and less heat in the winter I guess.
John: That kind of brings us back to this ectotherm-endotherm piece, right? Like, and I think you were focused on the mosquito and not the bird in that case. Talk to me about why.
Dawn: Well, because external temperature does not drive what's going on in the bird, per se, since it self-regulates its body temperature, whereas the mosquito can't do that. So temperature really does affect these cold-blooded insects and other relatives of theirs in a very important way. Temperature and precipitation are really the two driving factors, because precipitation is necessary for the mosquito to survive, to have a place to lay its eggs, and for its larvae to develop and get to the next generation.
John: Mosquitos and birds or course, but mosquitos in particular are good at finding microhabitats and refugia from temperature, right? What are some common refugia for mosquitos that we should know about?
Dawn: Yeah, well, some of the mosquitos that are really important actually have the ability to over-winter in the egg stage, and that gets them through the cold, freezing temperatures and they come back out in the spring. But many of them do not have that ability. And so they will hang out under houses--we have a lot of raised houses here in New Orleans that have little nooks and crannies where they can hang out. They'll go in carports and garages and just hang out up in the corners in dark, semi-humid areas. They'll go into things like cavities in trees that are protected. Any sort of little habitat that's protected from the wind and from direct rain, it will provide them with a place to hang out. And they kind of go into a stupor or torpor. They don't truly hibernate, so when it warms up they'll become active again. And I was - in fact, today I saw some mosquitos out in my yard. You know, they obviously made it through the freeze last week and were doing just fine, looking for somebody to feed on. So yeah, those are the types of little harborage that they'll use to get through. So that's part of their temperature. And, you know, there may be some birds that are nesting in or near some of those habitats, as well. So when they do wake up in the spring and start looking for something to feed on there could be nestling birds or other birds right near there. The other thing that happens with regard to precipitation is when it gets really hot out--so later in the summer when we get - start to get into the high 90s, maybe over 100 degrees--it becomes drier, water sources shrink, and so both birds and mosquitos need water. And so often it's sort of counterintuitive that drought-like conditions can actually drive viral amplification and infection of new hosts, because everybody's got to get to that water source. And so birds and mosquitos come in closer contact, and that can drive viral amplification as a result.
John: How interesting. It's funny, as you were saying that I was thinking about a map of the United States. And this is kind of a narrative that I've been developing, which is, you know, tropics at least in the Northern Hemisphere are moving north, bringing with it, you know, humidity, rainfall intensity, heat. And then aridification is moving from the west to the east. And I was trying to imagine, I wonder what the hot spots look like and how they change. And it sounds like it's not easy to predict if drought in fact is driving behavior of hosts to water. That's really interesting. Talk to me about what your vision is for, or scenarios in your mind about where these tropical vector-borne diseases will move, say, in the next 20 years or something like that.
Dawn: Well, I think we're already seeing in the last decade or two the almost annual transmission of things like Dengue virus in the United States. And this was not the case for many decades. And a part of that is definitely warming climate and the dense southern cities where these mosquitos thrive. The other part that we're all so interested in, and we haven't really touched on yet today, is human movement. And air travel from areas of endemic transmission of many of these viruses into the U.S. is becoming more and more common.
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John: Up next, Dawn explains why rising temperatures are altering mosquito habitats and virus transmission rates, and what strategies can help mitigate the growing risks.
John: We've seeing higher incidences of vector-borne disease from the tropics in Florida, Texas, Louisiana, in the south, places that are subtropical. What does that look like in the future?
Dawn: I think we're going to continue to have more and more of these local transmission events occurring, not only with the Dengue and Zika, and possibly Chikungunya, which is another one that has a similar transmission pattern, but also with malaria. We've recently seen a number of locally-transmitted cases of malaria, and I think that's to me a little concerning as well. It's been quite some time since we've had that happen at the numbers we've seen recently. West Nile is going to continue obviously, too, but it's a more temperate virus. We'll probably see it moving further north. We'll probably see more evidence of West Nile transmission in places like Canada, for example, where they have it but it's not real common, you know, in a given year. So I think we should expect that.
John: So that's kind of scary, and I don't like this podcast to be scary.
Dawn: Right.
John: I like to think about solutions. So let's kind of shift gears towards, you know, what do we do? How do we combat the tropics moving north and tropical diseases becoming more common in the U.S.?
Dawn: That's another good question, and I think the answer really relies in resources and in getting the information that we need to be able to focus on controlling these different viruses and the particular mosquitos that transmit them. So I work closely with local mosquito districts, mosquito-control districts, both here in New Orleans and in other parts of the state, and across the region, and some of them are very well-funded and, you know, do their own sort of operational research, which all allows them to focus on specific questions that they know are important in their area, and others are not. Others are just reacting; they spray on a timed basis. They don't look to see whether it's really necessary to spray, which of course is not a safe thing to do, that can result in insecticide-resistance developing in mosquitos, and people being exposed to insecticide when they shouldn't be. So having the ability to - for someone like me, who does research in these areas, to work on things that I can focus on identifying information that's important to them I think is really what we need to do going forward, and developing models that can help us say, "Okay, this is when the risk is highest," and have the models themselves be flexible enough that we can continue to update them going forward. Because conditions are going to change within five years to ten years. And also to have a really strong surveillance system in place so that when new things are introduced--whether it's a new virus, a new mosquito species--that we can react to that appropriately.
John: Really interesting. When I give talks about climate change in the Mississippi River Valley - which is a huge area, right--you grew up in part of it--31 states - U.S. states, and covers, I can't remember, 40-plus percent of the continental U.S. landmass. So just as a background, I've spent tons of time in Ecuador, and you and I have both spent considerable time in South America and in Ecuador. The last time I was in Ecuador, on the way back from the field site we drove through a small town where they were fogging in front of us. So when I give this talk I often say, "Can you imagine that we actually have to fog the French Quarter?" And, you know, it's a little bit of a guise, right, to get people to think about, "Oh, it could be bad," right? Talk to me about what we do - like, what are some of the measures - practical measures that mosquito-control districts take to, you know, fight this battle.
Dawn: Well, there's a variety of different things that they'll do. The two main life stages of the mosquito that are targeted are the larval stage, which is the one that's present in water, and the adult stage, which is the one that flies around and obviously feeds on you, takes your blood, and uses that blood to develop eggs that can then go back into the system. So there are larval-control methods and there are adult-control methods. And in general in the United States we do our best to use compounds that are either very bio-friendly, in that they're not a true insecticide, per se. There's a couple of different compounds that are good larvicides--so larval-control compounds--that are actually produced by bacteria. And when the larva ingests or eats these things as it's feeding in the aquatic environment, those bacteria, they're basically a toxin that the bacteria produces, will kill the larva within a day or so. And those are pretty widely used. And there's some other ways that can be utilized as well. But in a good control program they start early in the spring, if it's seasonally-based--and usually it is here in the U.S.--they start early in the spring to assess the mosquito populations, including the larval populations, and attempt to control the larvae first. So that's where you start. If you can suppress the larvae up to a certain point you can suppress the adults. Usually at a certain point through as the season goes on and it gets warmer, and it maybe rains a lot, you can't just use larval control, because you're going to start seeing a lot of additional adult mosquitos out there. And usually if the program is a good program they're doing surveillance where they're trapping the adult mosquitos, identifying them, and looking to see who's out there and how numerous they are. Because they know who the important ones are, who the vector species are, and who the other species are. In Louisiana, for example, there are over 60 mosquito species, and only a few of those are vector species. And so you've got to know who's there and where they are to be able to control them. So as the season progresses you start seeing increases in your adults of an important vector species, and that's when you may start to try to target those adults. Here in Louisiana we have two ways that we target adults, either through trucks spraying--the spraying that you just mentioned from Ecuador where it's kind of a fumigation type thing--or aerial spraying, either by helicopter or by airplane. And so - and there are different compounds that can be used for the adult spraying, but those are true insecticides--they're chemicals that are highly licensed and that can only be sprayed by licensed professionals.
John: Wow. Okay, so we covered sort of chemical-control. What about bio-control? Have there been any success stories there, or is it...?
Dawn: There have. And true bio-control is basically finding some kind of a predator that will eat either the larvae or the adults. There have been no successes for adult bio-control, even though people, you know, will say things like purple martins, or bats, or [CROSSTALK] dragonflies feed on mosquitoes. The fact is, they may feed on mosquitos, but they also feed on other insects. And they don't feed on enough mosquitos to impact the population to any noticeable level. However, there have been successes in larval bio-control, and the best-known one is... First let me back up. So if you think about the animals that live in water and eat in water, there's a few things out there, right? There's fish - and we have something in our local marshes here called "mosquitofish," and they are voracious feeders on mosquito. They don't get very big. The bigger a fish is, the less-interested it becomes in a mosquito larva, because a mosquito larva doesn't get that big. So gambusia or "mosquitofish" only get to be about a couple inches long, and they're very good controllers of mosquitos. The problem is you have to have an environment that's relatively healthy and big enough for them to survive in. So one of the things following Hurricane Katrina, when the City of New Orleans was very - was empty - somewhat empty, and there were lots of abandoned swimming pools that became - you know, the chlorine was gone, people weren't back--they became mosquito-production factories. Our local mosquito-control professionals went out and collected gambusia fish from the marshes and brought them in, and put them in these abandoned swimming pools, and very effectively controlled these essentially mosquito-production factories in the aftermath of Katrina. And that's been done in other parts of the country and world. That's been published, and we know that works.
John: My PhD advisor would be so happy about that narrative, top-down control. That's her gig. So glad you brought that up.
Dawn: Yeah. Small turtles, like little turtles that kids keep in their - you know, as pets, those turtles will eat mosquito larvae. And again, as they get bigger they get less interested in larvae. There are these little aquatic creatures called "copepods" that a certain species have been found to be very predatory on mosquito larvae. And they've been successfully used in areas of southeast Asia to control the mosquito that transmits Dengue virus in water-holding containers. They basically just put some of these things in there and make sure when they get the water out they sieve it through a mesh so that the copepods don't get, you know, drunk with the water, or (inaudible) with the water. They've been able to successfully eradicate Dengue from villages in the area where they use these things.
John: Wow.
Dawn: So those are some of the best examples. There's also a predatory mosquito called "toxorhynchites," where the larvae of that mosquito cannibalize other mosquito larvae. And so you can release the mosquito out in the environment, it lays its eggs in habitat have mosquitos that you want to control, and they hatch out and eat up all the other larvae. The problem is, you have to keep reintroducing it. But most of these methods you have to keep an eye on it and reintroduce the predator on occasion.
John: What I like about this--and this is kind of where I was going with this question; it's related to what we're working on together--is if you're going to build nature-based solutions, green infrastructure in a city, to help abate stormwater issues, you're going to create mosquito habitat. And it sounds like the place where, you know, you gain ground on the mosquito side of that new nature-based solutions or mosquito habitat is by trying to control the larvae. And there are bio-control - successful bio-control methods for doing that, that could really help minimize exposure to tropical disease in those contexts, right?
Dawn: Absolutely, yeah, absolutely. The thing about larval habitat is that various species utilize different types of habitats. Some of them like to utilize manmade containers, some use natural containers like tree holes and plant axels, some like to breed in groundwater. Those habitat tend to be difficult to introduce predators into. So if you're developing green infrastructure and it's an environment that's designed to hold water and then drain water as the water seeps in, if there's a way you can manipulate the habitat to provide space for predators - for natural predators, that would be a good thing. Because, you know, when it rains again those predators are still there and can help you in controlling any mosquitos that are introduced.
John: Super cool, bringing me back to my roots - my PhD roots. So maybe to close out, talk to the listeners about, you know, something in research, or maybe in the application of research that you're really excited about that you think will have a big positive impact on the spread of tropical vector-borne diseases and managing them.
Dawn: So we've been--this is a little bit off-topic, but I think there's a connection that can be made--we worked - in the last few years we've worked with a group of bioengineers from Rice University. They had developed a synthetic vasculature that could be 3D-printed. So think kind of like a little auger chip that you can 3D-print to allow blood or other liquids to run through. And we had this idea that maybe we could get mosquitos to feed on this little chip that held blood going through it. And we were successful in doing that. And so we have continued to develop this system to be able to look at the process of a mosquito feeding on blood. So basically we're developing a sort of a model to use it as a pseudo-host to feed on, where we can deliver different kinds of blood. We can grow cells in that 3D matrix and see how they react to the mosquito's saliva, which is important for the feeding process. We can see how that differs if we put virus in that mosquito and it delivers virus, or if it acquires virus from the blood that we are using. The idea is that this could work as a host system that we can sort of dissect the process of virus-transmission either coming to the mosquito or going from the mosquito, and then begin to look at ways to control or knock out parts of that system in a very fine-scaled way. So that's something that just recently has kind of come into play that I'm really excited about seeing where it can go.
John: That sounds super cool. It's, you know, intersection between "field ecology," if you will, and technology, right? And, you know, where I thought you were going with that is, like, creating a filter for the virus or something like that. But rather I think your goal is to use it as a science tool to figure out key parts of the infection and transmission process that otherwise can't be really measured, because everything is a moving target, right?
Dawn: Right. Or you have to do part of it in a live animal, and you're limited to some of the things that you can do there as well. So it gives you just some additional flexibility.
John: And control, which is key.
Dawn: Yeah.
John: Really cool. That's super cool. Hey, thanks for being on the show with me. It's been really a great learning experience for me, as it always is, talking with you. And so I appreciate your time; thanks for being here.
Dawn: Sure, John. Thank you so much. I've really enjoyed it, too.
John: Cool.
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John: Okay, that's a wrap. I think one of the key takeaways for me in this episode is that vectors are complicated. Yeah, I know that's kind of a cop-out, but really, each disease has a host, sometimes those are humans and sometimes they are not the primary host. In the case of West Nile birds are the primary host and are most vulnerable in the spring during nesting season, because the nestlings are literally sitting ducks. Humans can't carry a high enough viral load to pass it on to others through mosquito blood, but they can get the disease, which can be deadly. What does all of this mean from a science perspective? Well, first, human travel through the air can move the virus to the U.S. from other countries. But birds are the source of transmission, so from a climate-change perspective the relationship between temperature and the virus, the mosquito, and the bird, is paramount. And since mosquitos are cold-blooded we call them "ectotherms," and birds are warm-blooded, we call them "endotherms," temperature will affect the co-evolution of the virus and the mosquito more strongly because birds regulate their body temperature and can move greater distances to avoid inhospitable heat. If it's too hot the virus doesn't fare well in the bug, but it does just fine in the bird, providing a refuge. Second, standing water is important for mosquito habitat and breeding, hence climate-adaptation strategies like green infrastructure in cities that are aimed at reducing stormwater flooding may have unintended consequences of providing habitat for breeding mosquitos. As the tropics move north we need to be mindful of how our adaptation strategies for one transformation--here, rainfall intensity--may have unintended consequences for another transformation like tropical disease. So maybe the bottom line is that climate change and climate adaptation are complicated. The five climate transformations can indeed interact, and the intervention portfolio that we undertake to achieve adaptation needs to address these possible interactions to avoid unintended consequences.
John: That's it for this episode of Audacious Water. If you liked the show please rate and review us, and tell your colleagues and friends. For more information about Audacious Water, and to find in-depth show notes from this episode, visit our website at AudaciousWater.org. Until next time, I'm John Sabo.
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END (AUDACIOUS WATER EPISODE 9 SEASON 4)