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Rat Fleas
Measuring about the size of a nail, the rat fleas carry very harmful germs that can even prove to be fatal. The Yersinia pestis bacterium is one of the most famous of such germs. This bacterium was responsible for causing Black Death in the fourteenth century, which lasted from 1348 to 1350 and caused more than 350 million deaths in Europe. Though fleas are also found on cats, dogs and other animals, they are not as deadly as the rat fleas.
