Image: © The Pierpont Morgan Library/Art Resource

The Black Death killed about a third of Europe’s population, between 1347 and 1351. But not until 1894 did the Swiss scientist Alexander Yersin identify the pathogen that caused the plague, a bacterium later named Yersinia pestis. Shortly thereafter, scientists showed that fleas escaping from dead infected rats carried the bacterium to humans.

It is often assumed, since the cause was not scientifically understood in their day, that people of the Middle Ages did not associate plague with rats. Well before the outbreak of the Black Death, however, there was some understanding of the connection. The evidence is found in medieval manuscripts recounting and illustrating an episode in the Bible known as the Plague of the Philistines, or the Plague of Ashdod.

In 1 Samuel 5–6, the Philistines capture the Ark of the Covenant and place it in the temple of their god Dagon. The next day, they discover that the statue of Dagon has fallen on its face before the ark. The Lord inflicts a plague upon five Philistine cities in retribution for the ark’s theft, and in a number of medieval manuscripts depicting this calamity, rats figure prominently.

One example (above) can be found in a French picture Bible known as the Morgan Bible, completed at the court of Louis IX sometime between 1244 and 1254. In the upper left quadrant of the illumination are five pedimented structures meant to represent the five Philistine cities ravaged by the plague. Bodies are strewn at the base of the walls and portals, and rats swarm over them. The corpses include the unbearded young as well as the old, and a peasant (in cap) as well as city dwellers. The rats bite them all over, especially on the neck and armpits, places where the buboes—painfully swollen lymph nodes—of bubonic plague are found, though other parts of the body are attacked as well. Blood drips from the bites. Beside the representation of the cities stand six men: Five are the leaders of the Philistines and one is the priest, or diviner, counseling them on how to rid their cities of the plague.

One of the textual sources available to the master who would have directed the illustration of this Bible was the Vulgate, translated from Hebrew to Latin by St. Jerome sometime between 382 and 405. Jerome’s Vulgate makes no mention of rats in this episode, but says only that God struck the Philistines “in the secret parts of the buttocks” (percussit in secretiori parte natium), a phrase that has generally been taken to mean that God struck them with emerods, or hemorrhoids.

The oldest surviving version of this story, however, is found in the Septuagint, the Greek translation of the Hebrew Bible dating from the third century B.C. The Septuagint does connect rats with the Philistine plague. In 1 Samuel 5:6, the text reads, “The hand of the Lord was heavy upon Ashdod, and He brought evil upon them, and it burst out upon them into the ships and rats sprang up in the midst of their country, and there was a great tumult of death in the city.” From the detailed description of the plague that follows, including mention of its attack on the “hidden parts,” or groin, medical authorities have long recognized that the disease was most likely the bubonic plague. This and other evidence suggest that a link between rats and plague had been established in textual traditions during the Middle Ages, which is why rats appear in some medieval paintings.

Adapted from “Mice, Arrows, and Tumors: Medieval Plague Iconography North of the Alps,” a chapter by Pamela Berger in Piety and Plague: From Byzantium to the Baroque, edited by Franco Mormando and Thomas Worcester. Copyright © 2007 by Truman State University Press. Reprinted with permission. Berger is a professor of art history and film and Mormando an associate professor of Italian at Boston College.