Ticks are a growing problem, no matter where you live

Summary

Podcast Summary: Short Wave – "Ticks are a growing problem, no matter where you live"

Date: June 30, 2026
Hosts: Regina Barber, Producer Hannah Chin
Guests:

• Dr. Andrea Sway (Disease and Vector Ecologist, San Francisco State University)
• Dr. Adela Oliva Chavez (Medical Entomologist, University of Wisconsin-Madison)
• Dr. Jean Tsao (Disease Ecologist, Michigan State University)

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Episode Overview

This episode investigates the growing problem of ticks and the expansion of tick-borne diseases, particularly Lyme disease, across the United States. Hosts Regina Barber and Hannah Chin, along with expert guests, explore the ecological, biological, and behavioral factors that help ticks thrive, how they spread disease, the unexpected role of lizards in Lyme transmission, and new developments in vaccines and prevention. The tone is lively, humorous, and accessible.

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Key Discussion Points & Insights

1. The Mystery Origins of Lyme Disease [00:26–02:30]

• Historical context:
  • Children in Lyme, Connecticut, developed arthritic symptoms in the late 1970s.
  • "Children aren't supposed to have arthritis. So this sort of alerted public health officials to something kind of funny going on." – Dr. Andrea Sway [00:40]
  • By the early 1980s, Lyme disease was traced to the spirochetal bacterium Borrelia burgdorferi, transmitted by ticks.
• Connections to land use changes and increased human contact with tick habitats were highlighted.
  • "It probably increased in prevalence in that time due to a number of land use changes and sort of human settlement pattern changes that put people in higher contact with infected ticks." – Dr. Andrea Sway [01:44]

2. Lyme Disease Geography and Tick Expansion [02:12–02:42; 13:10–13:58]

• Primary hotspots: Great Lakes and Northeastern US, over 95% of cases.
• "But, Gina, scientists know that ticks are on the move. So tick country... is expanding." – Hannah Chin [02:15]
• Factors in expansion:
  • Climate change, altered land use, urban wildlife (deer in urban spaces).
  • Ticks are now found in city parks and green spaces; recommended: check yourself for ticks even outside traditional “tick country.” [13:13]

3. Tick Biology, Life Cycle, and Infection Process [04:11–06:19]

• Four life stages: egg, larva, nymph, adult; require a blood meal at each stage.
• Only two tick species spread Lyme in the US: black-legged (deer) tick and western black-legged tick.
• Ticks aren't born with Lyme; they acquire bacteria from infected animal hosts.
• Infection pathway:
  • Bacteria enter a tick's stomach from blood meal, bind to gut lining, and later migrate to salivary glands for transmission during feeding.
  • "The bacteria will come with the blood that the ticks are taking. It will go to the meat gut that is the stomach of the tick... they will bind to that lining." – Dr. Adela Oliva Chavez [05:01]
• Timeframe matters for transmission:
  • "If you remove the tick in those 24 hours, you won't get sick." – Dr. Adela Oliva Chavez [06:30]

4. Geographic Differences: North vs. South [06:47–09:10]

• In the north, tick infection rates are high (40–60% of adult ticks).
• In the south, infection rates are much lower (as little as 0.2%).
• Differences stem from host animal preferences:
  • Northern ticks feed on small mammals and birds (better reservoirs for Lyme).
  • Southern ticks feed more on reptiles, especially lizards, which can neutralize the bacteria.
• "Ticks in the north tend to feed on small mammals... Ticks in the south tend to look for hosts on the ground... more often reptiles like lizards." – Hannah Chin [07:49]

5. The “Lyme-Killing” Superpower of Lizards [08:32–10:34]

• Western fence lizards can clear Lyme bacteria from infecting ticks:
  • “After feeding on this lizard, even previously infected ticks would become Lyme free.” – Hannah Chin [08:32]
  • Protein in lizard blood destroys the Lyme bacterium (Borrelia burgdorferi).
• Other small reptiles and some mammals (e.g., adaptive rabbits) can also “detox” ticks.
• Removing lizards, paradoxically, decreases Lyme prevalence:
  • Because lizards host far more ticks, their absence means ticks struggle to find blood meals and die off.
  • “If you look at a lizard, they'll have on average 25, 30, sometimes up to 100 ticks on them.” – Dr. Andrea Sway [10:12]
  • “Pulling on one thread isn't going to do the thing that you think it will because it's connected to these other factors.” – Dr. Andrea Sway [10:34]

6. Can We Leverage Lizard Science for Humans? [10:51–12:15]

• Creating a “lizard blood” Lyme vaccine for humans is unlikely—proteins effective in reptiles don’t generally translate to humans.
• However, scientists are developing anti-tick vaccines to train immune systems to kill ticks:
  • Ticks feed slowly (3–7 days), suppressing the human immune response through their saliva proteins.
  • The new strategy: "We're educating your immune system to recognize those proteins so that they can inactivate them so the tick now activates your immune system and then your immune system can kill the tick." – Dr. Adela Oliva Chavez [12:37]

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Notable Quotes & Memorable Moments

• “Children aren't supposed to have arthritis. So this sort of alerted public health officials to something kind of funny going on.” – Dr. Andrea Sway [00:40]
• “So this bacteria that causes Lyme disease, it goes straight to the tick stomach lining and it just like camps out there.” – Regina Barber [05:21]
• “If you remove the tick in those 24 hours, you won’t get sick.” – Dr. Adela Oliva Chavez [06:30]
• “Ticks in the south tend to look for hosts on the ground below the layers of leaves on the forest floor. So... more often reptiles like lizards.” – Hannah Chin [07:54]
• “After feeding on this lizard, even previously infected ticks would become Lyme free.” – Hannah Chin [08:32]
• “If you look at a lizard, they'll have on average 25, 30, sometimes up to 100 ticks on them.” – Dr. Andrea Sway [10:12]
• “Pulling on one thread isn’t going to do the thing that you think it will be because it’s connected to these other factors. And it's just really complicated.” – Dr. Andrea Sway [10:34]
• “We're educating your immune system to recognize those [tick saliva] proteins so that they can inactivate them so that the tick now activates your immune system and then your immune system can kill the tick.” – Dr. Adela Oliva Chavez [12:37]

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Practical Takeaways

Eliminating Risks

• Tick checks: Always check yourself and your clothes after being outdoors, especially as tick territory grows.
• Early removal: Catching and removing a tick within 24 hours dramatically reduces Lyme risk.
• Tech tools: Consider using The Tick App for local tick info and identification ([13:58]).

Science Frontiers

• Watch for new developments in anti-tick vaccines, a promising direction for Lyme disease prevention.

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Timestamps of Important Segments

• [00:40]: Emergence of Lyme disease as a public health mystery
• [01:44]: Land use and increased human-tick contact
• [02:15]: Ticks and Lyme country are expanding
• [05:01]: How ticks become infected and transmit Lyme
• [06:30]: The 24-hour rule for safe tick removal
• [07:49]: Differences in tick hosts North vs. South
• [08:32]: Discovery of lizards’ Lyme-killing blood
• [10:12]: Why lizards can make things more complicated for tick control
• [12:37]: Anti-tick vaccine research
• [13:13]: Causes for the tick territory expansion
• [13:58]: Resources for tick awareness (The Tick App)

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Conclusion

Final Message:
Ticks and tick-borne diseases like Lyme are now a concern outside their traditional territories. Understanding their biology, the delicate and surprising dynamics of their ecosystems, and advances in science (like novel vaccines) is crucial for prevention and personal health. Everyone, no matter where they live, should be proactive about tick checks and staying informed.

Closing Quote:
“One of the biggest functions of these lizards is being a meal for these ticks to thrive and stay alive and then mate. And detoxing the ticks’ blood of this Lyme-carrying bacteria is kind of a smaller function.” – Hannah Chin [10:19]

Transcript

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[Hannah Chin]

You're listening to Short Wave from NPR.

[Regina Barber]

Hey, Short Waivers. Regina Barber here, and today I am joined by producer Hannah Chin. Hey, Hannah.

[Hannah Chin]

Hey. So today I want to start our episode with a mystery.

[Regina Barber]

Ooh.

[Hannah Chin]

It starts the way a lot of old mysteries start. With a group of kids in a tiny town in the middle of the woods.

[Regina Barber]

No, it's a horror movie.

[Andrea Sway]

In the late 1970s, a small cluster of children came down with arthritic symptoms. And, you know, children aren't supposed to have arthritis. So this sort of alerted public health officials to something kind of funny going on.

[Regina Barber]

This is actually terrifying. Like, where did these kids live?

[Hannah Chin]

All these kids lived in Connecticut around a little place called Lyme. And as public health officials investigated, they started to trace it back to the woods. They were like, okay, there's some kind of illness. We don't know what it is. Maybe it's an insect or a virus or a bacteria or something, but we know it's coming from the forest.

[Andrea Sway]

So it wasn't until the early 1980s that the organism was identified as Borrelia burgdorferi, a spirochetal bacteria that was transmitted. Transmitted by ticks.

[Hannah Chin]

This is Andrea Sway. She's a disease and vector ecologist at San Francisco State University. And she says this bacterium had probably been around for a while, maybe even millennia. This was just the first time that we noticed it and, like, had the tools to track it down.

[Andrea Sway]

It probably increased in prevalence in that time due to a number of land use changes and sort of human settlement pattern changes that put people in higher contact with infected ticks.

[Hannah Chin]

And nowadays, Connecticut is still a hotspot for Lyme disease. In fact, if you look at a map of Lyme cases, I actually looked at the CDCs just now. The vast majority of them, like, more than 95%, are in the Great Lakes area and the northeastern U.S. so we're

[Regina Barber]

talking about, like, the upper right hand corner of the United States.

[Hannah Chin]

Yeah, exactly. And historically, that's what we think of as tick country. Right. But, Gina, scientists know that ticks are on the move. So tick country, and by association, Lyme country is expanding.

[Regina Barber]

So today on the show, we're doing a tick check, shortwave style.

[Hannah Chin]

We're taking a long, hard look at ticks, what we know about them, what helps them thrive, and how they acquire and spread Lyme disease.

[Regina Barber]

Plus why their territory is spreading, maybe even into your backyard. You you're listening to Shortwave, the science podcast from npr.

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[Regina Barber]

Follow us to make sure you never miss a new episode. New ones drop every Monday, Tuesday, Wednesday, and Friday.

[Hannah Chin]

Okay, Gina, so we're going to start with like tic 101. Get ready to be a little bit grossed out.

[Regina Barber]

I love school. Let's do it.

[Hannah Chin]

To start, these arachnids have four stages of development. Egg, larva, nymph, and adult. After they hatch, they need to have blood meals at every single stage in order to survive.

[Regina Barber]

Right. It's these blood meals that. That's when they get infected with the disease.

[Hannah Chin]

Exactly. And there's only two kinds of ticks that carry Lyme in the US there's the black legged tick or deer tick, and the Western black legged tick.

[Regina Barber]

Okay, I don't know why that makes me feel a little better.

[Hannah Chin]

And to be clear, these ticks aren't born with Lyme. They only get infected when they feed on an infected animal, like a bunny or a bird or a deer or a human. Okay. And I asked Adela Oliva Chavez about this process. She's a medical entomologist at the University of Wisconsin, Madison.

[Adela Oliva Chavez]

The bacteria will come with the blood that the ticks are taking. It will go to the meat gut that is the stomach of the tick. And in the stomach of the tick, they bind to the epithelial cells. So the Lining of the mid gut of the tick, they will bind to that lining.

[Regina Barber]

So this bacteria that causes Lyme disease, it goes straight to the tick stomach lining and it just like camps out there.

[Hannah Chin]

Exactly. And again, ticks only feed once per developmental stage. Right? So say the larva feeds on an infected host. That same larva will molt into a nymph and then that nymph is now infected and looking to feed. And that's the first time that it can infect other hosts like us.

[Adela Oliva Chavez]

When the tick then bites the human, the blood comes into inside of the tick and the change in temperature inside of the tick because the blood that is coming is around 37 degrees.

[Hannah Chin]

And Adele is using Celsius here, so it's like 98.6 degrees Fahrenheit.

[Adela Oliva Chavez]

So.

[Regina Barber]

So that's the temperature of a human, right, when I'm healthy.

[Hannah Chin]

Exactly. And this temperature trigger, Right. For healthy human blood tells the bacteria in the tick that it's time to replicate. It's time to start moving from the stomach to the salivary glands of the tick. And that's when the transmission process begins.

[Regina Barber]

So this is all happening during like the feeding process where the tick is like on. On us?

[Hannah Chin]

Yes, and that's why the CDC gives this recommendation that you should try to find and remove ticks if possible, within the first 24 hours.

[Adela Oliva Chavez]

There is a lactine, it has to start taking the blood in the bacteria has to replicate and then it's transmitted. So if you remove the tick in those 24 hours, you won't get sick.

[Hannah Chin]

And that's how ticks transmit Lyme disease.

[Regina Barber]

Okay, gotcha. But earlier you said that there are way more Lyme disease cases in like the Great Lakes and the northeast area. So why is there such a difference geographically?

[Hannah Chin]

Yeah, I wanted to know this too. So I talked to a disease ecologist. Her name is Jean Sao, and she specializes in tick borne diseases at Michigan State. She told me there's a variety of different factors at play here. Right. Temperature, humidity, habitat. And we're not going to get into all of them.

[Regina Barber]

Yeah, that's a lot.

[Hannah Chin]

But one big one is that Lyme seems to be more endemic in the north, maybe just because it's been circulating longer. So your probability of getting infected is higher. In the north, 40 to 60% of the adult ticks are infected with the Lyme bacterium, depending on where you are. But in the south, if you look at the adult ticks, it's very low, like 0.2% at a place where we collected a lot of these Ticks. Wow.

[Regina Barber]

Okay, so it's like if you're rolling the dice, right, and there are fewer infected ticks, you might get bitten, but your odds of getting Lyme disease is pretty. Is still pretty low.

[Hannah Chin]

Yeah, it's really just a probability thing. And another factor is in the ticks themselves. Right. The animals that they feed on. And the way they get to them is different. In a number of studies that Jean and her colleagues worked on, they found that ticks in the north tend to feed on small mammals. So birds, rodents, like squirrels and mice and chipmunks, as well as humans. And ticks in the south tend to look for hosts on the ground below the layers of leaves on the forest floor. So sometimes birds, but more often reptiles like lizards. Andrea Sway, who's the researcher that you heard at the beginning, says this is true of her California ticks, as well as they seem to prefer lizards. And this is really important because it turns out some of these lizards have a superpower. They can clear the tick systems of Lyme disease.

[Regina Barber]

That's so cool.

[Hannah Chin]

Yeah. So Back in the 1990s, a group of researchers looked at a key host for ticks on the west coast, the western fence lizard. And they discovered that after feeding on this lizard, even previously infected ticks would become Lyme free. Later studies found a specific protein in the lizard's blood that killed the Lyme disease bacteria, Borrelia burgdorferi. Completely wiped it out, cured the ticks.

[Adela Oliva Chavez]

Cool.

[Hannah Chin]

And Dina, get this. It's not just the western fence lizard. Other small reptiles like the eastern fence lizard and the southern alligator lizard, they also have this Lyme killing blood. There's a white tailed deer too. And I know some rabbits can adapt after multiple tick bites to cleanse sticks of Lyme.

[Regina Barber]

This is so fascinating. Okay, so could we just bring these lizards everywhere and get rid of Lyme disease, like, for good?

[Hannah Chin]

You'd think that would work. I thought the same thing too.

[Adela Oliva Chavez]

Yeah.

[Hannah Chin]

But I talked to Andrea, and she said when she was in grad school in California, she did this experiment where her team removed the western fence lizards from an area just to see what would happen.

[Andrea Sway]

We actually found the exact opposite impact. So when we removed the lizards, Lyme disease prevalence and infection went down.

[Regina Barber]

What? Why?

[Hannah Chin]

I was confused about this too, but it actually does make sense.

[Andrea Sway]

What's unique about the California system is that the lizards are so important for feeding the tick. So if you go out and you see sample a bunch of animals, which my lab has done, you'll find, you know, a smattering of ticks on wood, rats and mice and. And squirrels, on the order of maybe one to eight ticks per animal. But if you look at a lizard, they'll have on average 25, 30, sometimes up to 100 ticks on them.

[Regina Barber]

So they really like lizards. I see. Okay, so if they have less to eat, then they might die, right? That makes sense.

[Hannah Chin]

Yeah. In other words, one of the biggest functions of these lizards is being a meal for these ticks to thrive and stay alive and then mate. And detoxing the ticks blood of this lyme carrying bacteria is kind of a smaller function.

[Andrea Sway]

I think what it shows us is these systems are incredibly complex, and pulling on one thread isn't going to do the thing that you think it will be because it's connected to these other factors. And it's just really complicated.

[Regina Barber]

Okay, so it's very complicated. But these lizards, they basically clear lyme disease with their blood. So could we make something similar in a lab, then use it to help defend humans against Lyme disease?

[Hannah Chin]

Probably not. Unfortunately, just because a protein works in lizards doesn't necessarily mean it'll work in for us humans. But there is good news. What if I told you that scientists are working on a vaccine that could train our immune systems to kill ticks?

[Regina Barber]

Great, let's do that.

[Hannah Chin]

So Adela Liva Chavez, she's the medical entomologist, she's working on something like this. It's called an anti tick vaccine. And it hinges on this key fact that ticks are really slow feeders.

[Adela Oliva Chavez]

The feeding process of the tick, depending on the life stage, goes from three days all the way to seven days. So for those seven days, the tick has to be able to be attached to you and not die because your immune system is killing the tick. So what they do is they use their saliva. They inject the saliva into your skin. The saliva will target certain cells, immune cells and cells in your skin, and reduce the immune response so it doesn't get killed. The pathogens get a free pass. They go like, yeah, we can infect. The immune system is reduced.

[Hannah Chin]

And so Adela and her colleagues thought, all right, what if we could just get the immune system to recognize and attack the tick instead of being reduced.

[Adela Oliva Chavez]

So my laboratory is trying to take those proteins that are being injected into

[Hannah Chin]

the human, the ones that are in the tick saliva. Right.

[Adela Oliva Chavez]

And instead of them affecting your immune system, decreasing it, we're educating your immune system to recognize those proteins so that they can inactivate them so that the tick now activates your immune system and then your immune system can kill the tick.

[Hannah Chin]

And all of this is increasingly important, Gina, because tick territory is expanding. Ticks are coming further north to Canada, further west to, say, Minnesota, and even becoming more common down south.

[Regina Barber]

Yeah, we talked about this earlier. Do we know why that is?

[Hannah Chin]

Not really. All of the experts told me it could be a number of things. Warming temperatures due to climate change, increased development and land use in once rural and undeveloped areas. Even seemingly harmless things like deer are a major host for these ticks, and they're increasingly found in urban areas. So nowadays you might find ticks in city parks and green spaces, too. All of that means that even if you weren't living in tick territory before, or if you don't remember doing tick checks in the past, it's probably a good idea to start checking yourself and your clothes for ticks after you've been outside. One of the experts I talked to recommended the Tick app. It has information about tick counts in your local area, instructions on what to do if you're bitten by a tick, and even a spot to submit photos and help you ID that tick.

[Regina Barber]

Han, this is really good to know. Thank you so much for bringing us this story.

[Hannah Chin]

Anytime, Gina.

[Regina Barber]

This episode was produced by Rachel Carlson and edited by showrunner Rebecca Ramirez.

[Hannah Chin]

Tyler Jones checked the facts. Anlee Huang was the audio engineer. Special thanks to Maria Dirkwasser. I'm Hannah Chin.

[Regina Barber]

And I'm Regina Barber. Thanks for listening to Short Wave from N.

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