Short Wave - Tick Check! Meet Your Backyard Bloodsuckers

Episode Date: July 5, 2023

We hope you had a restful holiday! Maybe even got outside for some relaxing fresh air. If so, you might've come across cute and not-so-cute critters like ticks. With ticks in mind, we're heading to Big Thicket National Preserve in Texas. Among the trees and trails, researchers like Adela Oliva Chavez search for blacklegged ticks that could carry Lyme disease. She's looking for answers as to why tick-borne illnesses like Lyme disease are spreading in some parts of the country and not others. Today, what Adela's research tells us about ticks and the diseases they carry, and why she's dedicated her career to understanding what makes these little critters ... tick. (encore)See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. On clear days between October and April in Texas's Big Thicket National Preserve, you can spot groups of researchers wandering the trails. We live early in the morning, about eight, drive for about two hours, until we get to a big ticket. That's Adela Aliva Chavez. She's a medical entomologist, a field all about the tiny critters that make us sick. And she wears a pretty specific outfit.

to hunt for her favorite arachnid, ticks. We are wearing light clothes, so something white, something peach, like a light color, so that if by any chance we get any ticks crawling on us, we can see them. As they walk through the preserve, they do something called dragging. So we come with a piece of white cloth that is attached to a piece of wood.

It's being dragged on the floor, so it's on the vegetation on top of. of the vegetation and it just passes and brushes through. We count to 10 or 100 while we walk, stop, and check if we have an adult tick. We put it in a bile containing a solution that preserves DNA and RNA. Adele's fascination with ticks began early in her life. I grew up in a farm, in a cattle farm in Honduras, and in the cattle, you see a lot of the ticks and also in people. When I was a kid, my twin sister actually felt ill.

At the time, doctors didn't know what was making her sister sick. They later determined she had a vector-borne disease, meaning it was transmitted from something like a tick or a mosquito. Adela's sister got better with antibiotics, but the experience stuck with Adela. She dedicated her career to studying these kinds of diseases to prevent this kind of thing from happening to more families. They actually have such a big impact. the livelihood of the farmers and also like people getting sick with diseases that cannot be diagnosed because nobody knows what they are. Today on the show, we revisit a researcher's quest for accessible solutions for Lyme and other

tick-related diseases. I'm Regina Barber and you're listening to Shortwave, the Daily Science podcast from NPR. So first, let's talk about what's happening with ticks in the wild. There are many different kinds of ticks around the world, and only a few species suck on us humans and spread disease. In the case of the United States, the most prevalent betoporn diseases are tick-borne diseases. From those, the most commonly diagnosed disease here in the United States is Lyme disease. Lyme disease is generally found in black-legged, aka deer ticks, in the eastern half of the U.S.

Once an infected tick bites another animal like a human, it takes about a day for the bacteria to spread, though ticks can suck out nutrients much longer than that. Ticks feed on you for up to seven days and just stay there until they get completely engorge. For reference, they start as small as a poppy seed and feed up to... 100 times their weight in block. So you can see like they are about like a quarter size. Adela says it's crucial to remove the tick in the first 24 hours. If you don't remove the tick in that window, the bacteria can spread.

And then, Adela says, Lyme disease can take hold and be tricky to catch. many people don't realize they have it. Unless you have one particular sign that is what we call the bull's eye, it's where the tick bite you. As the bacteria is disseminating in your skin, it produces an inflammatory reaction. So you see redness, like a circle that is red. And this process takes some time because there are changes that happen in the tick.

And while they're feeding, molecules in their saliva trick your body's immune system. So imagine like when you have a cot, you have a lot of immune cells that come and try to fix where the cut is, right? In the case of the tick, the tick tells them, hey, I want to feed, so stop. You're not fixing anything. Like Jedi Mindtricks. Yeah, like Jodah telling them something like fix cut knot, something like that. We mostly think about this as an East Coast problem.

But? So I'm scared of ticks. I'm so glad you said that they're mostly in the northeast. Because I live in the Pacific Northwest. Oh, well, you have another one over there. So species that you have will be exodus pacificus. Ticks are all over the country. Some ticks and the Lyme and other diseases they carry, they've started popping up in unusual places.

Take the black-legged tick. It's expanding through the northeast, upper Midwest, and mid-Atlantic. One place they're not. not Big Thicket National Preserve in Texas. Which is exactly why Adela is comparing ticks from Big Thicket to ticks and say Minnesota. She wants to understand why Lyme disease infections are rising with the spread of these black-legged ticks and not with the ones in Big Thicket. It starts with how ticks find their hosts.

Ticks have this behavior that is called questing. That's how they get into their hosts. And this questing behavior, what it is, is ticks go up into the vegetation, like a piece of grass, something that they go up to, and then they start waving their front legs. Then as the host passes, they latch with the front legs, and that's how they get into a host. Adela found that this questing process is different depending on where the ticks live.

In Minnesota, they will go up to the top of the vegetation, and they start doing the questing. are waving their legs from side to side. The ones here in Texas don't do that. And we believe that it's because it's so hot here that they would lose too much water if they weren't up in the vegetation. So they are staying low in the vegetation. So when an human is going hiking, all happy into the trails,

they are less likely to encounter ticks if they do it here in Texas than if you do it up north in the northeast or in Minnesota. Adela also says black-legged ticks in Texas feed on lizards, which are less likely than small rodents to get infected with the bacteria that causes Lyme disease. If fewer ticks are infected, they're less likely to transmit the disease to humans later. In Minnesota, you can find up to 50% of the ticks infected with something. Here in Texas, the infection rates are a lot lower. This difference in how they act isn't the only thing contributing to the spread of ticks and tick-borne diseases.

Global warming changes in human behavior and also the way that we are killing the predators that will normally keep deer and mass population down because if they are not host for the ticks to feed on, then the population of the ticks do not thrive. Black-legged ticks tend to like hotter, more humid climates. So as climate change intensifies, we might see longer tick seasons. adding a growing population headed out to the suburbs.

Before we tended to live in cities only, now we're living in suburban areas. So we are coming into the areas where the ticks are. So you can go to your backyard and actually get ticks in your backyard. Recently, because of her large body of work, the United States Department of Agriculture awarded Adela a grant to start developing a vaccine for cattle, to protect against the cattle fever tick.

Her ultimate goal is to create a vaccine that will protect humans from ticks too. And once we see what proteins and what candidates work with cattle, it will be a proof of concept that we can do this. We can kill ticks feeding on a vertebral animal to then move into humans, developing a vaccine that will prevent tick feeding on humans and the spread of different pathogens in humans.

This episode was produced and fact-checked by Rachel Carlson. It was edited by Rebecca Ramirez. The audio engineer for this episode was Andy Huther. Before we head out, a quick shout out to our Shortwave Plus listeners. We appreciate you and thank you for being a subscriber. Shortwave Plus helps support our show and if you're a regular listener, we'd love for you to join so you can enjoy the show without sponsor interruptions. Find out more at npr.plus.org backslash shortwave.

I'm Regina Barber. Thanks for listening to Shortwave, the Daily Science podcast from NPR. You just gave me a master class in medical entomology. I teach a whole class if you want to take it. Maybe I do. I don't have to now. I just aced it.