Black Death Spread by Human-Borne Fleas, Lice? Not Rats?

The Black Death plague that killed millions hundreds of years ago was spread by filthy humans carrying fleas and lice, not by rats, a new study suggests.

It was widely thought that rodents were responsible for the devastating pandemic that swept through Europe from 1346 to 1353, causing 75 to 200 million deaths, according to The Telegraph.

Now scientists from the University of Oslo and the University of Ferrara have challenged that age-old theory, suggesting instead that body lice and fleas living on humans and their clothing could have been the culprit all along.

The study, published on Monday in the Proceedings of the National Academy of Science, used previous data to simulate disease outbreaks and to provide scientists with a clearer understanding of the Black Death.

"We have good mortality data from outbreaks in nine cities in Europe," Prof Nils Stenseth, from the University of Oslo, told BBC News. "So we could construct models of the disease dynamics [there]."

Nils and his colleagues considered three possible ways in which the disease could have spread: rats, airborne transmission and fleas and lice that live on humans and their clothes.

Based upon their findings, Nils said seven out of the nine cities they studied showed the "human parasite model" as the most likely pattern to fit the outbreak, based on how quickly it spread and how many people were affected.

Rats have played a role in the spread of modern plagues and based on this, many experts believe that rats were also responsible for spreading the Black Death pandemic.

“Geneticists and modern historians were putting the rat into the position [of spreading the plague] and were straining bits of evidence,” said Samuel Cohn, a University of Glasgow medieval historian who has criticized the rat-flea theory, according to National Geographic.

However, schools of thought have considered the possibility that the plague had spread by fleas and lice carried by humans, which may have transmitted the disease from one person to another.

Lead study author Katharine Dean said that, when it comes to the topic of plagues, the cause is something that always draws hot debates and this latest research would likely stir controversy.

However, she noted that it was important to understand how the plague was spread and why it happened so quickly.

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