Fleas are ectoparasitic blood-sucking insects with the ability to jump, which commonly infest wild and domestic animals (mainly dogs and cats) but also humans.
Plague is caused by the bacillus Yersinia (Y.) pestis, belonging to the family of the Enterobacteriaceae. It evolved several thousand years ago from Y. pseudotuberculosis.
Plague is caused by Yersinia pestis bacteria. Blood sucking fleas transmit the bacteria among animals, and various species of rodents can become infected.