Or maybe more specifically, a tick bite. Which is not wrong, you should.

But what exactly is it about a tick bite that makes us sick?

This is Borrelia burgdorferi, one of many bacteria that ticks can pass onto humans and

the one responsible for Lyme disease.

It causes an array of symptoms, which can be anything from fatigue, arthritis, facial

palsy and occasionally a bulls-eye rash. (Erythema migrans, if you want to get technical).

We’ve only known about the pathogen since the early 1980’s, but it’s been around

for much longer than that...potentially for thousands of years longer.

Traces of its effects were even found in Otzi the Iceman, the 5,300-year old hunter found

mummified in the Italian Alps.

But while we’re not sure exactly where and when Borrelia originated, we do know a lot

about how the disease works and how it’s spread.

My name is Raphael Stricker.

I'm a medical doctor. I practice in San Francisco.

I have more than 4000 Lyme disease patients in my practice.

And I've written more than 200 papers about Lyme disease.

Ticks have been called sewers of infection.

Anything that they feed on they can pick up and transmit to you.

These “sewers of infection” need blood to survive.

Sometimes that’s bird blood, sometimes that’s reptile blood, but a lot of the time its mammal

blood, like mice and deer.

If a tick feeds on one of those animals and they are infected with the bacteria, the tick

will carry it and then spread it to other animals, who then spread it to other ticks,

and so on.

Occasionally, those ticks spread the disease to us, and they do that by passing the pathogen

through the tick’s saliva, which some people call a pretty fascinating substance.

Tick saliva is really a pretty fascinating substance.

It has several components.

One is it has an anesthetic that numbs the bite site so that the person doesn't know

that he or she is being infected.

It also has an anticoagulant that keeps the blood from clotting so that the tick can feed

continuously at that site. And then it also has this immunosuppressive substance that

suppresses the immune response at the bite site so that the host can't fight off the infection.

And it's been shown that a tick bite can inject about 70,000 bacteria with the lyme bacteria,

so you're getting a pretty hefty dose of this spirochete, it's called a spirochete, with a tick bite.

So, what does Borrelia burgdorferi actually do to your body?

Technically....nothing.

The bacteria itself doesn’t harm your cells, but your body knows the pathogen shouldn’t

be there, so it launches an all-out assault.

Your immune system will first try to fight off disease by targeting proteins on the bacteria’s

cell walls, but the spirochete can just change which proteins it expresses and evade detection.

So, so much for that idea.

Then, as the pathogen moves through your bloodstream to other parts of your body, your immune system

continues to fight it by producing cytokines, which work to regulate your immune system

and produce inflammation.This inflammation then occurs in the areas that the bacteria

travels to, which, depending on the strain of Borrelia, can occur in the joints, muscles,

heart and even the brain.

But due to the bacteria’s ability to evade detection, this inflammation does nothing

to destroy it and everything to make you feel sick.

So that's what really causes the symptoms.

It's not the bacteria per say it's the body's response to the bacteria that causes a lot

of these symptoms.

Basically, Borrelia burgdorferi isn’t doing much of anything other than trying to survive

in its host.

Well my medical school teacher told me not to anthropomorphize you know bacteria,

basically I mean the goal is to survive.

The goal of any bacteria or any organism is to survive.

So Borelia has evolved a way to do that that's very efficient.

Of course, we're doing whatever we can to make sure the disease can't survive.

Currently lyme disease is treated with antibiotics.

And while a vaccine was created around 16 years ago, it’s no longer being produced

due to low usage and potential side effects.

But there is interest in developing a new vaccine in two different ways.

One idea is to target the proteins expressed by the Borrelia itself, which fights lyme

disease, while the other idea would involve fighting the compounds in tick saliva, which

would fight lyme as well as a number of tickborne diseases.

Because ticks are, after all,

Sewers of infection.

So, if ticks, mice, deer and any other number of animals can be infected with Borrelia burgdorferi,

why don’t they also get Lyme disease?

So deer have a kind of protein in their blood that kills the Lyme bacteria.

And the question always comes up well why don't why can't we put that into humans?

And the answer is because humans aren't deer.

So there you go, humans aren't deer.