[Dr. Franklin]

Fun facts: lice are species specific. Human head lice feed only on humans, so can only spread plague by first being infected by a human. So lice can’t start a plague epidemic on their own.

Cram a hundred humans into a trailer rig. All it takes is one human with a disease like Bubonic Plague and one head louse jumping around to spread the disease.

And bed bugs have been around for thousands of years and have never been known to transmit any disease to humans ever.

Lice were known to transmit Trench Fever. Why can't they spread plague?

[mewzilla]

If you'd like to geek out, your answer may be found here...

A refined model of how Yersinia pestis produces a transmissible infection in its flea vector

Ick.

[Valpal1]

Because they don’t. Not every insect can be a vector.