Deep Look

To pet a dog is to know peace.

But whos this interloper?

Thats a brown dog tick.

Theyre the most widespread tick in the world, and the most adapted to living among us.

Brown dog ticks are thought to have evolved alongside burrowing carnivores like foxes and weasels and came indoors when we domesticated dogs.

They can be found in and around homes.

And whats worse, they spread bacteria that can be deadly.

They arent the ticks known for carrying Lyme disease.

Those are blacklegged ticks.

The brown dog tick has grooves along its back, and theyre a solid, reddish brown.

See the difference?

No matter what kind of tick they are, they want one thing: blood.

And to find that blood, they use whats called the Hallers organ, one near the tip of each foreleg.

Ticks use them to pick up chemical signals from the air: carbon dioxide, pheromones and humidity.

Scientists believe the Hallers organ even lets ticks detect the body heat of their prey.

All ticks have them, but they use them differently.

The blacklegged tick quests it stays put, waving its forelegs to sense when it can hop aboard a host.

The brown dog tick hunts, using that Hallers organ to home in on a potential target.

As its name suggests, a brown dog tick is happy to take all its meals from dogs.

But in the right conditions, the brown dog tick will dine on you, too.

Thats a problem, because they can transmit bacteria that cause Rocky Mountain spotted fever, a terrible disease that can kill both dogs and humans.

Rocky Mountain spotted fever usually occurs in small clusters in the United States and is relatively rare.

But outbreaks in northern Mexico have killed hundreds of people.

And rising temperatures due to climate change are sparking some troubling tick behavior.

When its particularly hot out, brown dog ticks start craving human blood.

To investigate this, University of California, Davis researchers put a very good dog in a box and a very good human in another, connected by a plastic tube with hungry brown dog ticks inside.

Dont worry theres a screen here and here.

The ticks cant actually get them.

At room temperature, the ticks preferred dogs.

But when researchers heated up the tube, to 100 degrees Fahrenheit, brown dog ticks preferred you guessed it us.

Scientists are still trying to determine why.

In the meantime, researchers are developing vaccines to protect us from the disease.

Tick treatments can keep the pests off of dogs.

But theyre expensive.

In the Sonoran Desert, in Southern California, volunteers remove ticks by putting their tweezers right up against a dogs skin and pulling straight up.

This one is full of dog blood.

And they give the dogs oral medicine for free.

Look at these happy pals!

And then its back to the petting frenzy you both deserve.