Talk about pests. Fleas are parasitic, meaning they usually live on other creatures without killing them. In fact they need their host’s heart pumping, so that they can suck their blood. But this doesn’t mean that fleas are harmless. In fact, they have been one of the deadliest things for humans in history.
Pulex irritans is the scientific name for the Human Flea but even dog or cat fleas prefer human blood. Fleas can carry many diseases; the most serious being Yersinia pestis or plague (known in the Middle Ages as the Black Plague). They can transmit this directly or through rats and other rodents.
The ease with which fleas transmit diseases is what’s made them so deadly. During the Middle Ages when man brought rats containing the Yersinia pestis virus to Europe from Africa. This is what sparked the Black Plague, which claimed more lives than all the wars in human history.
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