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The Black Plague

There are many theories on what the Black Plague really was and how it was spread throughout Europe. Here I’ll present the version that claims the Black Plague was, in fact, the Bubonic Plague as well as explanations for its rise, proliferation, and disappearance.

The bacterium that is thought to have caused the Black Plague is  believed to have originated in Asia. At the time, Asia was populated with rats known as Black rats (Rattus rattus). These rats were carried to Europe along trade routes, carrying with them fleas containing the bacteria, Yersinia petis. This bacteria causes the Bubonic Plague which we know from descriptions of the Black Plague in Europe. As these rats would die, their remains would stay on the streets of towns and cities. It was these remains that began the spread of the Plague. As the rats infested more areas of Europe, so did the Plague, leading to an epidemic.

However, there is a second type of rat known as the Brown Rat (Rattus norvegicus). This is the type of rat that most domestic rats are descended from. These rats are much larger than the Black Rat and eventually displaced the Black Rat in Europe. Brown Rats are less susceptible to carrying the fleas that acted as the vector for the bacteria that causes the Bubonic plague. Thus, when the Brown Rat displaced the Black Rat, the epidemic ended, and the Bubonic Plague  disappeared from Europe. In other words, the ancestors of domestic rats actually ENDED the Black Plague, rather than causing it.

The other thing to note is that the disease was carried by fleas on the rats, rather than the rats themselves. Fleas were a more common occurrence then, infesting animals as well as people. Lower personal hygiene in European populations during the Middle Ages may also have exacerbated the problem. Finally, doctors at the time had limited knowledge on microscopic organisms due to the lack of technology. Therefore, there was little understanding about what caused disease, how to treat it, or even how to prevent it in the first place. In conclusion, all these factors makes it exceedingly difficult to blame the spread of  the Black Plague on rats.

Information found at:

Rattus norvegicus image found at:

Rattus rattus image found at:

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