Note: the following transcript is a radio script and contains audio cues and other quirks (including imperfect grammar) of the medium. It may contain typos.
Mary Montgomery - Is that a tick right there?
Colleen Evans - Yup the big nasty thing right there? Yeah
Mary Montgomery - Wow!
Colleen Evans [4] - So this is Amblyomma varium, the female she’s about the size of maybe a green grape... [fades down]
This is Colleen Evans — figurative cryptkeeper for one of the world’s strangest zoological attractions, one composed entirely of dead parasites.
Colleen Evans [2]: I’m the collections manager, for the US national tick collection.
And right now she’s talking to lucky college student Mary Montgomery — who we hired to tour the collection with a microphone — a big fat bloodsucker... a species of tick that feeds exclusively on Central American sloths.
Colleen Evans [8] - Any animal really you can think of, there’s probably a tick that feeds on it.
Mammals, sure - that you probably knew… but did you know ticks feed on birds…
Colleen Evans [10] - … ticks from penguins and puffins… all kinds of animals.
… they feed on reptiles… there’s even a species that has evolved to survive underwater, by feeding on sea-snakes.
Colleen Evans 34 - And what they do is they actually go inside the sea-snakes ears.
There are ticks on every continent in the world. Including Antarctica. They have achieved this awesome feat by virtue of being hard to detect, and hard to remove from the animals upon which they feed.
Colleen Evans [18] - And this one is my particular favorite… cosmiomma hippopotamensis… Again it’s very pretty, it’s got a lot of ornamentation. So they’re very gold. But also they feed very specifically on hippopotamus… but very specifically inside their anal canal. So they feed inside hippopotamus butts. And it’s one of those things … [fades down]
The scientific name for ticks is “acari”… Like Atari, with a C instead of a T.
They’re not technically insects, but like spiders and mites, they hail from the arachnid family… and usually - grape sized anomalies aside — they’re tiny. Acari comes from the greek… roughly, it means “a small thing.”
Which reminds me of a quote from Lord of the Rings.
[LOTR clip] Boromir: It is a strange fate that we should suffer so much fear and doubt over such a small thing.
In spite of the name, from an epidemiological perspective ticks are hardly small. Ticks are one of the most efficient carriers of disease on the planet. They’re Trojan Horses… Miniature warships in disguise…sailing the bodies of animals everywhere, and transporting an army of pathogens inside their bellies.
Colleen Evans [3] - The way that ticks are stored is in jars and in vials. And any vial can have 1 to thousands of ticks in it depending… [fades down]
This collection - hardly more than a single carpeted room, crammed with head-high filing cabinets has at least one million of these little bastards, the oldest of which were collected more than a hundred years ago.
Colleen Evans [13] - We have some ticks collected during the Smithsonian Roosevelt safaris in the early 1900s...
But the tick we’re primarily concerned isn’t unusually big or beautiful … it doesn’t hide inside the ears of snakes, or other more exotic places. It wasn’t collected by a former US president.
It’s a generalist, happy to feed on any number of small to medium sized mammals or birds. A humble arthropod, just bigger than a a poppy seed.. A small thing.
Colleen Evans [19] - This one is Ixodes Scapularis.. so that is the deer tick. That’s the one that’s associated with Lyme Disease.
[cue theme]
I’m Taylor Quimby. Do you remember the name of the bacteria that causes Lyme Disease? It’s okay if you don’t - it’s a weird name. Borrelia Burgdorferi. Say it with me - BORRELIA BURGDORFERI!
[Crowd of people shout Borrelia burgdorferi very badly, without confidence, mispronunciations, and not at all in sync with one another!]
I get it. Lyme disease is confusing. And a lot of that confusion is because nobody has ever taken the time to explain the basic biology of the disease. So today we’re taking a break from the history and controversy surrounding Lyme. We're going to shrink your butt down like Mrs. Frizzell and take you on a magic School bus podcast ride into your body, and inside the body of a deer tick… which from here on out, we’ll be calling by a more accurate name… The black-legged tick. What IS Lyme disease? How does it get in you? And what does it do once it's there?
This is the part we know.
Before we get to the parts that we don’t.
This is Patient Zero.
<<<<<>>>>>
Monica Gulia Nuss [5] - There is just so much to learn, I could never get bored of them...
This is Dr. Monika Gulia-Nuss, assistant professor of molecular biology at the University of Nevada Reno - a woman who has spent much of her career studying mosquitoes, and ticks.
Monica Gulia-Nuss [2] - People call me “bug lady.” So…
TQ: Well they’re both gross.
Monica Gulia-Nuss - Well I don’t think so, I think they’re beautiful.
The humble black-legged tick. There’s a lot about these parasites that we’re going to save for a future episode — the way they get around, what they eat, how they get Lyme disease themselves … all great questions but ones we’re putting aside for the time being. Instead we’re going to focus on the head.
Colleen Evans [26] - Ticks don’t have a head, that’s a common misconception. Ticks are sort of weird sacks of body parts.
Monica Gulia-Nuss [29] - Most of their body really consists of gut.
Unlike insects, which you may remember have three body parts - the thorax, abdomen, and head - the black legged tick has a tear shaped body… and a thing on top. It’s not a face. It has no eyes. It’s totally blind. scientists often call it by a very gross, very memorable name. The mouthparts. These are the bits that work their way into your skin.
On the outside are the palps, which as the name suggests are used to feel around for a good spot to bite. In between them are two sawed blades that rub themselves into the skin , and then flex backwards - which pulls the most important part — a spiky sort of tube — into your body.
That tube has backward facing barbs, sort of like a harpoon so that it’s hard to pull out of your body. And once it’s embedded inside the skin, the tick can start secreting special chemicals through it like a straw, and spitting out all sorts of stuff to help prepare it’s meal.
Colleen Evans [24] - Ticks in that first 24 hours are not feeding… they’re doing things like injecting you with antihistamines...
Antihistamines… so you don’t get a big welt, which might tip you off to the fact that you’ve got a tick inside you.
...anticoagulants...
Anticoagulants… so your blood doesn’t clot.
...they locally immunosuppress you, they have cementing agents…
Cementing agents, to literally bond the tick’s mouthparts to your body.
...they’re doing all this other stuff in order to make sure that you don’t know you’ve been bit.
Ticks have so many superpowers in this moment - that we’re actually using them to make better drugs for humans. There are anticoagulants on the market - synthetic blood thinners - derived from similar compounds excreted by leeches and ticks.
Once they’re done doing all of this… numbing you, glueing to you, medicating you, prepping their meal… then, after a good day or more… they start do drink in earnest.
Monica Gulia-Nuss [26] - At the same time as they’re taking blood they’re also secreting saliva into our bloodstream.
Secreting saliva. Aside from being gross, this is maybe the most important thing that’s happening - because if a tick were ONLY drinking blood, then it wouldn’t be so good at spreading disease. It’s the spit that the Lyme pathogen uses to travel into your body.
Do you remember what it’s called? Borrelia Burgdorferi!
[Crowd shouts Borrelia Burdorferi, with more confidence and generally sounding better than the first time]
Nice.
Now I’ve got some good news and some bad news. First the good news: You won’t contract Lyme Disease the second a tick burrows into your skin. Some refer to this as the 24-48 rule… but biologically, why would that be.
Do you remember where Willy Burgdorfer found the Lyme Disease spirochete?
Alan Barbour - So he provided me with some of the intestines of these ticks… [fades down]
Inside one of the tick’s organs… the midgut.
That’s where Lyme Disease is hiding… waiting for just the right moment to begin multiplying.
Sam Telford - Replication takes resources.
This is Sam Telford, a medical entomologist and long time lyme researcher. And what he’s saying is that, for a bacteria to grow and multiply and move… it’s going to need some energy… food. And that food comes from the host… the tick feeds on you… but Lyme feeds on the tick.
Sam Telford -That’s not good for your host… You’re using their fat reserves, which means they’re less fit, that’s a negative selection pressure, so what’s really happening is that the bacteria goes dormant.
[SFX cuts out]
Translation: If the Lyme bacteria grew willy-nilly all the time, it could harm its gracious eight legged hosts - the ticks. Kill them even. And then the bacteria would never spread somewhere new - it would be the end of the line, so to speak.
So instead, the bacteria goes to sleep, nestled in the tick’s midgut… Like a sci-fi film astronaut cryogenic deep-freeze chamber… traveling to new worlds, and new frontiers… on autopilot.
But once the tick thrusts it’s mouthparts inside your skin… the temperature goes way up… a sign that the bacteria, the astronaut, has arrived at its desired location.
Sam Telford - The change in temperature from ambient to your skin, that temperature differential is a signal for the bacteria, and the other pathogens transmitted by the ticks to wake up.
After the tick has done all the work to prep it’s meal, it starts drinking blood. That gives the bacteria a food source too… so it can multiply without hurting the tick. And it starts traveling from the midgut, up to the tick’s salivary glands, where eventually, it can get spit out into a new host.
Again, the process takes time. Thus, the 24 to 48 hour rule.
Sam Telford - And so it’s not just the fantasy that it’s 24-48 hours because we say it is. Empirically there are studies because some poor graduate student had to sit up all night and pull ticks off every 12 or 6 hours and see whether the animal became infected.
If you can’t tell by his tone, Sam Telford knows this subject - like nearly all of them in Lymeworld - is a little bit controversial.
And that’s because, if you start hanging out in Lymeworld, there is a different narrative… anecdotal stories about people who get bit for just a few hours… but still get Lyme Disease.
So what’s the story here? Why the discrepancies?
For starters, even the experts will acknowledge that the 24 to 48 hour rule is more like a guideline than a law of gravity. Ticks do not operate like clockwork, and you could get Lyme after only 23 hours of feeding. It’s just less likely.
And there is another explanation that I find especially interesting.
Some ticks may have started feeding on an animal kickstarted the replication of Lyme Disease… only to fall off their host, find a new one and bite again. These are referred to as “pre-fed ticks”.
Sound unlikely? Maybe.
But when I was in Lyme Connecticut, knocking on doors along Joshuatown Rd, where the first few cases of Lyme disease were reported in the 1970s, I couldn’t help but notice that nearly all of the people I met there had dogs.
[quick dog montage]
So what happens if a tick with Lyme Disease bites your dog, then gets knocked off on your carpet or bed, only to climb up your leg and dig in?
Evidence show s if that happens transmission time can be much lower. One study on mice found 83 percent of pre-fed ticks gave their host Lyme in less than 24 hours.
The messiness of the real world is hard to recreate in the lab. If you get a tick off you quickly it is very unlikely you’ll get Lyme, but can we say 100 percent for sure you won’t?
I would humbly say no - because almost nothing in science is 100%.
[mux/static stab]
And this is where I’ll tell you the bad news. Remember, good news and bad. The bad news, is that there’s there’s one more, frankly much more plausible, explanation for why people think they get Lyme after just a few hours.
Ticks are small. And some of these reports probably come from people who were bitten by two ticks… maybe even weeks apart... but only noticed the second bite. You can’t pull off a tick if you don’t know it’s there.
[mux/static swell and cut off]
<<<<<<>>>>>>
Taylor: Remember The Magic Schoolbus?
[clip of Mrs. Frizzle humming something or other]
In the third episode, Ralphie - the one who wears a green shirt with an R on it, for some reason - he gets a fever. So radical elementary school teacher Ms Frizzle shrinks the titular Magic schoobus, and takes the class on a tour of the human body.
[clip 10:57] But I thought blood was red? That stuff is clear! [fades down]
The reason I’m talking about this absolute classic is because I’m about to rip off this classic sci-fi concept wholesale,
So let’s zoom in... to figure out what happens once the pathogen that causes Lyme enters your body.
[Party sound effects]
The tick is crawling, undetected. It finds a good spot - inside the moist, warm cave of a human armpit. It cuts its way into the skin… and pulls it’s mouthparts into place, and starts swapping fluids with you… the host.
And along for the ride are a bunch of corkscrew-shaped bacteria... spirochetes... The agent of Lyme Disease.
[Crowd very confidently whispers “borrelia burgdorferi”]
Alan Barbour [29] - The most important thing is that it’s just a single cell. It’s a very simple organism.
You may remember the dulcet tones of microbiologist Alan Barbour here… he’ll be our guide on this fantastic voyage.
Alan Barbour [32] - but what it looks like is like a snake on the ground. And it has this kind of… um… these little motors that have, sort of, hair-like projections coming out of the cell, and like an out-board motor… you know that’s rotating… and that gives the motion to the bacteria.
Remember those little motors, they’re gonna be important later on. But zoom in even further and you’ll notice that it’s skin, so to speak, is very textured. In fact, it almost looks like it’s covered in weird little spikes.
Alan Barbour [37] - Spikes… or I would say it’s more like a forest with trees, the canopy on top.
These are outer surface proteins. Why do you care about them?
Because they stimulate your immune system. Your body makes immune cells that respond to the specific shape of that little canopy of trees. You can get Lyme Disease more than once because different strains of Borrelia have different arrangements of spikes, so you’re body doesn’t immediately recognize it if you get it again.
These proteins are the key component of the Lyme Disease vaccine, called Lymerix, that was commercially available in the late 90s… and the key component of the lyme vaccine that you can still get today… for your dog.
Alan Barbour: this is a very ancient form of responding to pathogens that we share with fruit flies and worms and things like that.
In Lyme Disease, the immune system is… well it’s sort of everything. It’s the system that will hopefully fight off the infection, but it’s also what triggers your symptoms… the flood of stuff that sweeps in to fight off an illness: white blood cells, immune cells, and little chemical messengers that call for backup; all of it brings inflammation
Alan Barbour [58] - A lot of the symptoms that people experience, some of the signs of the disease, are from the inflammation itself and not because the bacterium is producing a poison or a toxin or something like that.
Inflammation is even the mechanism that causes the characteristic bullseye rash of lyme disease… In order to make way for all your immune cells, the blood vessels in your body dilate - they get bigger - which means more blood is flowing through them, and on the outside, it can make your skin look red.
But strangely, the center of the bullseye is where you’d be least likely to find the bacteria. Because it’s using those little outboard motors... motoring away from the tick, setting off the alarms as it goes, and making a break for it.
Alan Barbour [27] - The best place to find the bacteria at that point, would be just beyond that leading edge.
In other words… it’s a race. A race between your immune response, and the bacteria, which is trying to run and hide.
Okay. Let’s zoom back out.
This is called early lyme. And this early on, it’s still pretty much contained to the skin, around or at least close to where the tick bit you.
Around the same time as the rash, patients might start feeling some other symptoms - also caused by the alarm system that’s signaling the rest of the immune troops in their body. These would be Fatigue, mild fever, a headache... all pretty much standard stuff.
But sometimes - it is literally just the rash.
And here, I want to bring in our first case study, from a listener - who sent us this message. Her story is what I’ll call “The best case scenario”.
My Lyme story: I was diagnosed with Lyme’s when I was 18 years old and I was sharing a bed with an outdoor cat and I found a tick in my armpit one day and two days later the typical bullseye rash appeared and I had been just doing a report on Lyme disease for my health class in 12th grade so I knew exactly what it was and I went to the doctor that day got treatment antibiotics for a month and I was fine from then on.
Here’s some good news: For many, if not most of the 300 thousand plus cases diagnosed every year, this is pretty much the whole story: Lyme Disease is caught fairly quickly, and is treated without any serious lasting issues.
Which is not to diminish the seriousness of the horror stories, which can understandably freak people out - it’s just important to know that they are generally, a minority of overall cases.
So in a best case scenario, what happens next? The doctor orders a round of antibiotics — probably doxycycline — a drug that instead of killing the bacteria… sabotages its production… and stops it from multiplying.
Which gives the patient’s body time to build immune cells specialized to hunt down the specific shape of those outer surface proteins we were talking about, and gobble up the bacteria.
[mux drop]
And in a best case scenario, that’s exactly what happens. A couple days after taking antibiotics, the rash clears, the symptoms vanish, and all the patient has to deal with are the potential side effects from doxycycline: sun sensitivity, difficulty swallowing, constipation, dark pee, stomach cramps, diarrhea, discoloration of teeth... you know… the usual.
[mux]
So how often do cases of Lyme Disease resemble this best case scenario? It’s very hard to say, and here’s why:
In the early 2000s, Dr. Allen Steere - the same Dr. Steere who investigated the initial reports in Connecticut - published a study on the approximate number of people with Lyme Disease who get a rash.
And the answer is somewhere between seventy and eighty percent.
But of those, only 20 to 30 percent really get that textbook Bullseye look… Rashes might be oblong, or red throughout, or splotchy on the edges, or a little bluish in the middle.
In his paper, Steere acknowledged that the thousands who never get a rash, or whose rashes aren’t easily identified, may not go to a physician… and quote “lyme disease may not be recognized until the more debilitating, harder-to-treat late manifestations become apparent.”
If you’re one of those thousands who don’t get diagnosed… that little bacteria, with it’s little outboard motors… can outrun your immune response. It wins the race. It can lodge itself in your joints, in your brain, in your heart, and start to do some real damage.
The rash is the most obvious sign of Lyme disease. But the problem with an obvious sign, is that it can make you complacent — make it that you don’t pay attention to the subtle signs that are harder to see. And that in turn, can mean that there are a whole lot of patients that fall to the wayside.
Brian Fallon [50] - People who came into the office with an expanding red rash were the ones who enrolled in the research studies throughout the 80s and 90s and even today.
This is Brian Fallon, Director of the Lyme and tick Borne Diseases Research Center at Columbia University.
Brian Fallon [50] - And the reason is because there was no gold standard diagnostic test for early Lyme disease. So they had to rely on people who presented with a rash. That means that people who presented with viral like or flu like symptoms. Who didn't recall or see the rash. They were not being studied. It means that people who complained of severe fatigue and cognitive problems that started after a tick bite they were not being studied ...
[swell]
Today, we know lots more about what happens when Lyme disease isn’t a best case scenario — when the symptoms aren’t caught early — but we don’t know everything… and Lymeworld thrives on ambiguity.
Dr. Fallon: One of the problems with the Internet is that there's so much information out there it's very hard for patients to know what's real and what isn't real.
Tayor Quimby: It’s hard for reporters, I’ll tell you too.
Dr. Fallon: Yeah… and it’s hard for me too!
[radio, static, cuts off abruptly]
[mux]