Black Death was caused by humans not rats, says study

Computer modelling reveals human fleas and body lice are most likely vector of devastating first outbreak of plague

Harry Cockburn
Tuesday 16 January 2018 14:38 GMT
This 1348 painting shows how plague devastated European cities like Florence
This 1348 painting shows how plague devastated European cities like Florence (Interfoto/Alamy)

For centuries black rats have borne the brunt of the blame for the spread of the Black Death, which killed 25 million people across Europe during the first deadly pandemic in the mid-14th Century.

The plague was thought to have been largely transmitted by infected fleas living on rats, which would then bite humans. In total it is thought the disease has killed between 75 – 200 million people.

But has rattus rattus been unfairly accused of transferring the deadly bacteria?

Computer modelling carried out by a research team from the universities of Oslo and Ferrara suggests the first outbreak may not have been down to the rats, but instead can be “largely ascribed to human fleas and body lice”.

Using mortality data from nine outbreaks of the plague in Europe between the 14th and 19th centuries, the researchers plotted how the disease would likely spread by different means.

Seven out of the nine models indicated that transmission by human fleas and lice was the most likely cause of the disease’s spread, when compared to transfer by rats’ fleas, or airborne transmission.

In the paper, published in the Proceedings of the National Academy of Science, the researchers said: “While it is commonly assumed that rats and their fleas spread plague during the Second Pandemic, there is little historical and archaeological support for such a claim.

“Here, we show that human ectoparasites, like body lice and human fleas, might be more likely than rats to have caused the rapidly developing epidemics in pre-Industrial Europe.”

Speaking to the BBC, Profssor Nils Stenseth, from the University of Oslo said: “We have good mortality data from outbreaks in nine cities in Europe.

“So we could construct models of the disease dynamics [there].”

He added: “The conclusion was very clear. The lice model fits best.”

“It would be unlikely to spread as fast as it did if it was transmitted by rats.

“It would have to go through this extra loop of the rats, rather than being spread from person to person.”

Bubonic plague – believed to be the form of plague responsible for the Black Death – initially causes flu-like symptoms, and also causes lymph glands to swell up into painful “buboes”, often in the armpits, groin and neck.

People infected with plague require rapid treatment with antibiotics.

According to the World Health Organisation from 2010 to 2015 there were 3,248 cases reported worldwide, including 584 deaths.

Currently, the three most endemic countries are the Democratic Republic of the Congo, Madagascar, and Peru.

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