Asian gerbils, not rats, to blame for bubonic plague

Giant gerbils from Asia, and not the much maligned rats, may be to blame for the outbreaks of Black Death pandemic that swept across Europe, killing tens of millions of people, scientists say.
Researchers believe numerous outbreaks of the bubonic plague, which arrived in Europe in the mid-14th Century, trace back to gerbils from Asia.
"If we're right, we'll have to rewrite that part of history," said Professor Nils Christian Stenseth, from the University of Oslo.
The Black Death, which originated in Asia, arrived in Europe in 1347 and caused one of the deadliest outbreaks in human history, BBC News reported.

Over the next 400 years, epidemics broke out again and again, killing millions of people.
It had been thought that black rats were responsible for allowing the plague to establish in Europe, with new outbreaks occurring when fleas jumped from infected rodents to humans.

However, Stenseth and his colleagues do not think a rat reservoir was to blame.
Researchers compared tree-ring records from Europe with 7,711 historical plague outbreaks to see if the weather conditions would have been optimum for a rat-driven outbreak.
"For this, you would need warm summers, with not too much precipitation. Dry but not too dry," he said.

"And we have looked at the broad spectrum of climatic indices, and there is no relationship between the appearance of plague and the weather," said Stenseth.
The team believes that specific weather conditions in Asia may have caused another plague-carrying rodent - the giant gerbil - to thrive.
And this then later led to epidemics in Europe.
"We show that wherever there were good conditions for gerbils and fleas in central Asia, some years later the bacteria shows up in harbour cities in Europe and then spreads across the continent," Stenseth said.
The study was published in the journal PNAS.