Does It Feel Like Mosquitoes Are Getting Worse?
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Hi, everyone. Emily Kwong here. And this month's Nature Quest starts with one of our listeners, Abby Krishstar, who lives in Massachusetts. I grew up in the suburbs of Boston, and mosquitoes were terrible every summer. You know, I got tons of bites. I would swell up. It was so itchy.

And then in my 20s, I moved closer to the city and I realized that there were no mosquitoes. I could leave my door open or windows without screens and like bugs didn't come in. And for this brief period of time, life was divinely, blissfully mosquito free. And then I don't know when it was, maybe about five years ago, I started to notice that suddenly there were mosquitoes again. Just being in our backyard each year in recent years has become...

harder and harder. Like last year, we couldn't even be out there. Now she is locked in a battle with the mosquitoes of Cambridge. Her ping pong games with her husband outdoors are still getting cut short. Because we were just getting eaten alive. So Abby wants us to figure out what is happening? Like why is it that 15 years ago in Cambridge, Somerville, there were no mosquitoes and now like they're everywhere? What changed?

I hate mosquitoes, but they are more than just a nuisance. They are a public health problem. So I brought on producer Hannah Chin to talk about it. Hey, Emily. Yeah, the CDC considers mosquitoes the most deadly animal in the world, in part because they're a vector for a whole host of diseases. There's malaria and dengue globally, West Nile virus and eastern equine encephalitis in the U.S. It's a lot.

And what surprised me most, Emily, is that the same thing that's affecting mosquito populations in Cambridge and creating this spike that Abby noticed, it's also changing how diseases incubate and spread, which could really shift the landscape of scientific research.

Today on the show, we get to the bottom of this Massachusetts mosquito mystery. We're covering why mosquitoes bite, how climate change impacts them, and what experts recommend we do to keep the bloodsuckers at bay. You are listening to Shortwave from NPR.

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All right, short wavers, we are on a nature quest, our monthly segment that brings you a question from a fellow short waver who is paying attention to the environment around them and the ways it's changing. And this month, Hannah and I are investigating why our dear listener, Abby, is seeing more mosquitoes and what she and her neighbors can do about it. But let's talk about mosquitoes first, Hannah. Yeah, so I started by calling some local experts in eastern Massachusetts, and I asked them how

have they noticed more mosquitoes? Oh, absolutely. Yeah. So this is Doug Bidlack. He's an entomologist for the East Middlesex Mosquito Control Project. He's been working with them for the past 25 years. Our numbers have continued to go up since I've been here overall. And I'm talking about total mosquito populations have been going up. So, Abby, you are not imagining it. This is real. Did Doug tell you why, Hannah? Yeah. He says it's really tied to several different shifts in local weather and

All of them are linked to climate change. Okay, so how is climate change affecting mosquitoes everywhere? So it's kind of hard to generalize because there are like 3,500 different species of mosquitoes. Oh no, that's a nightmare. Yeah. In the Massachusetts area alone, there are over 50 different species of mosquito. And not all of them are thriving. For example, Doug told me that Aedes albopictus, commonly known as the Asian tiger mosquito, it's a non-native species they first started noticing in the area in 2017.

Those mosquitoes do really well in hotter temperatures, and so they've been thriving. But other species are declining, maybe because they don't do so well in those conditions. It's been warmer. It's been getting wetter. But it's also become more volatile, more unpredictable. So we have one year where it's very wet and hot, and one year where it's very dry and hot. So some species are, there's winners and losers because of that.

Overall, though, are there more mosquitoes in Massachusetts? Yes, that's what Doug said. And climate change isn't just affecting mosquitoes there. Last year, the Washington Post published a data analysis showing that in many parts of the U.S., mosquito season is multiple days or even weeks longer than it used to be. So again, like those hotter temperatures, increased rainfall, more volatile extremes. So the weather conditions that are good for mosquito life are...

is getting longer in much of the United States.

Does that mean that there are also more mosquitoes around the U.S. too? We don't know. That's because mosquito surveillance programs really vary across the country, so there aren't any exact numbers. But I talked to Rebecca de Jesus Crespo. She's an ecologist at Louisiana State University who specializes in mosquitoes. And she told me that these weather patterns are a pretty good indicator that overall, across species, mosquitoes could be thriving in these spots. If mosquitoes

you have an overall average trend of certain places getting closer to the ideal conditions where on average a mosquito would thrive, the locations where we already have a mosquito present, if those conditions expand temporally, you would have them there for a longer period of time. Yeah. Yeah.

I mean, that makes sense. More time to breed and make more of themselves. Exactly. And more time for them to spread diseases, which, by the way, is not the only thing that they do. So a lot of people think that mosquitoes are here on this planet just to bother us and bite us and annoy us. But that's not their goal. This is Julian Hillier. He's an entomologist at Vanderbilt University. And he says the goal of mosquitoes is the same as pretty much any other animal, right? They need to pass their genetic material on.

which means that the female mosquito needs to lay eggs. To make eggs requires a lot of nutrients. So the goal of drinking blood, which by the way, only females do, is to get the nutrients they need to make eggs so that they can pass on their genetic material to the next generation. But I will say, Emily, all those nutrients, they come with risks like bloodborne pathogens. When you take that blood meal, a female takes that blood meal, she'll drink anything that's in the blood.

So if a person is infected with something, she will drink that pathogen as well. So that when she takes another blood meal later on, that pathogen can be transmitted to another animal. And Julian says those pathogens are also affected by climate change because increased temperature changes how microbes might incubate in mosquitoes' bodies. Wait, tell me more about that. Okay, so humans are homeotherms, meaning no matter what the outside temperature is, our internal temperature remains constant.

Now, mosquitoes don't do that. They're poikilotherms, which means that they allow their temperature to fluctuate with the temperature of their environment. Whoa. So in a mosquito, when it's warmer, the metabolism is much higher. Everything's going faster when it's hotter.

And the idea is that they're also aging faster. For that reason, when you have warmer temperatures, mosquitoes generally have shorter lifespans. So Emily, when it's hot outside, it speeds up all of these processes in the mosquito life cycle.

So biting or laying eggs or fighting disease, spreading infections. So they could be out here living fast, dying young, but be more deadly on their way out. Yes. And then there's a lot of other things to consider, like the individual species or the particular pathogen or the local environment. It's all very, very complicated.

And not to throw one more wrench into it, but on a global scale, climate change is also causing mosquitoes' natural habitats to shift, which will also affect the pathogens that they spread. So the other thing that is going to be happening now is that you're going to have a geographical shift of what pathogens are where. Okay. So it's impossible to say, really. It depends on where you are.

how the local mosquitoes in your area are doing under your local specific conditions and how it intersects with their lifestyle and their natural habitat.

It's a very complicated question of, like, why so many mosquitoes where I live. Exactly. And it's a complicated question that is changing a lot, which is why doing science and continued observation and surveillance of these mosquitoes is really important. And both Julianne and Rebecca told me there are so many things that affect mosquitoes and their ability to transmit disease beyond just the climates.

the weather. There's the presence of humans or animals and the urban heat island effect and whether the mosquitoes are drinking enough water. Like whether they're hydrated or not? Yeah. Rebecca told me that matters too. If you are in a condition where it's becoming less humid and the mosquito feels dehydrated and there are not many water sources, then

It might bite humans more often kind of to quench their thirst. So they're drinking our blood also just because they're thirsty and there isn't enough water for them? Yeah, basically like if they're thirsty, they're going to be more aggressive biters. And you're more likely to attract those mosquitoes when it's hot out too. Like if your body is emitting heat.

CO2, it's sweating, it's emitting all those metabolites. Mosquitoes use chemical cues and cues regarding to the body heat to find a human to bite. Like if you're outside and it's hot, it leads mosquitoes to find you. What a stupendous summertime feedback loop we have found ourselves in. All right. So

Thank you for this incredibly thorough answer as to why so many mosquitoes. What does that mean, though, about living among them? How do we prevent mosquitoes from biting listeners like Abby? So I did ask our local experts what they recommend. And Doug said one of the things he'd tell Abby to do is check her backyard. Especially for like an Asian tiger mosquito or for the species that spread West Nile virus, which are Culex mosquitoes, the larvae live in containers.

It could be your gutters, for example. It could be a birdbath. It could be toys in your yard, that kind of thing. Really anything that collects even a little tiny bit of water, because mosquitoes tend to stay pretty localized after hatching. And a lot of those species don't fly very far. I mean, you might be getting your next-door neighbors, but you can cut down a lot on your own just from your own little property.

And the other thing that Abby and the rest of our listeners can do is keep an eye on local mosquito surveillance. Doug's team is regularly capturing and testing mosquitoes for the pathogens that cause West Nile virus and eastern equine encephalitis. And the Massachusetts Department of Health has an online dashboard they update regularly. It shows risk levels for every area in the whole state. We'll link to it in the show notes.

Vivian Tseng is the director of public health in Sudbury, just west of where Abby lives. And she says risk levels like those can help residents decide when to go out or when to stay in. The hours from dusk to dawn are peak fighting times for many mosquitoes. So as risk is increasing, consider rescheduling outdoor activities that occur during the day.

during the evening or early morning. Yeah, tough because Abby, like I said, she and her husband love to play ping pong out on their patio at night. What should she do about that? So Vivian says that if folks are working or playing outside or maybe planning a camping trip, basically, if they have to be outside, they can try to cover up with long sleeve and pants and get a good repellent. I'm a huge fan of

EPA-registered DEET repellents. I think that those are the most effective. And you definitely should check the product label to be sure on

if you're using it correctly. Important to say, though, not everyone loves DEET. You should check for the safety of the product, particularly for infants. And there are other alternatives, but DEET, I guess she's saying, is what's most effective. Yeah. Vivian also recommended permethrin spray, which you can spray on your clothes to repel insects. It'll last a certain number of washes, and she says it's good for things like camping. Awesome. Hannah Chin, thank you so much for tackling this question. Anytime, Emily. Thanks for having me.

Shortwavers, we are going to have NatureQuest on every last Tuesday of the month. So if you are observing something in your local environment and you want us to investigate with all the science might that we bring, email us your question at shortwave at npr.org. This episode was produced by Hannah Chin and Rachel Carlson. It was edited by Rebecca Ramirez and fact-checked by Tyler Jones. Jimmy Keeley was the audio engineer. Special thanks also to Sam Polson for writing the NatureQuest theme music.

Beth Donovan is our senior director and Colin Campbell is our senior vice president of podcasting strategy. I'm Emily Kwong. And I'm Hannah Shin. Bite that follow button like a mosquito for us. Thank you so much. Talk to you later. Bye.

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