The Black Death:

 

The Culprit: Oriental Rat Flea

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Siphonaptera
Family: Pulicidae
Genus and Species: Xenopsylla cheopis

The Black Death was one of the worst natural disasters in history. In 1347 A.D., a great plague swept over Europe¬†and ravaged cities, causing widespread hysteria and death. One third of the population of Europe died. “The impact upon the future of England was greater than upon any other European country” (Cartwright, 1991). The primary culprits in transmitting this disease were oriental rat fleas carried on the back of black rats.

Sources
Frederick F. Cartwright, Disease and History, Dorset Press, New York, 1991, p. 42.