LONDON — Maybe we owe rats an apology? For hundreds of years we have accused them of killing up to 200 million people in the Middle Ages by spreading the Black Death.
Turns out they were innocent.
The real culprits? Dirty humans.
A new study has found that parasites carried by rats were probably not behind the outbreak of plague in Europe.
The Black Death, one of the worst pandemics in history, devastated European populations between 1346 and 1353 and was caused by the bacterium Yersinia pestis.
It has long been thought that it was transmitted by fleas on the rats that arrived aboard trading ships. But now scientists at the University of Oslo and the University of Ferrara believe that “ectoparasites,” such as body lice and fleas carried by people, are more likely to be the guilty party.
Using mortality data from nine plague outbreaks in Europe between the 14th and 19th centuries, the teams in Norway and Italy tracked how pandemics developed. In seven of the cases there was a closer resemblance to the human model for outbreak spread compared with the alternatives.
The study, published in the Proceedings of the National Academy of Science, said: “While it is commonly assumed that rats and their fleas spread plague during the (14th-century) second pandemic, there is little historical and archaeological support for such a claim.
“Human ectoparasites, like body lice and human fleas, might be more likely than rats to have caused the rapidly developing epidemics.”
Black Death struck terror into medieval populations with symptoms including alien-looking swellings that oozed pus and blood and acute fever. Victims died within a week of infection. Previously scientists thought gerbils may have been to blame and a study in 2015 also examined warmer European climates as a possible culprit.
In the same year, a separate team discovered that the pathogen had been present for twice as long as previously thought. It found that Yersinia pestis was infecting people in Eurasia at least 3,000 years before causing the first known pandemic, the Plague of Justinian in AD 541.
The bubonic form of the disease, seen in the Black Death, is believed to have formed near the turn of the first millennium B.C. and was present in small quantities in Europe until the 19th century.
An outbreak of plague on Madagascar from August to November last year infected more than 2,000 people and killed 195. The World Health Organization said the risk of it spreading was low, but advised people to take precautions in South Africa, Tanzania and Kenya.