#11 Oriental Rat Flea
No one likes fleas but one of the worst ones is the Oriental Rat Fleas. This name might be unfamiliar but the diseases they carry probably ring a bell.
These fleas are responsible for the Bubonic Plague. Their main hosts are rodents but they can also latch onto other large mammals, which is a surefire way to spread disease.
Things like the Pneumonic Plague, tapeworm, and murine typhus are a few examples of diseases these fleas can carry.
If the black plague weren’t example enough, an infestation of these fleas can be disastrous.